May 2023, 令和四年度土木学会北海道支部技術研究発表会, 土木学会北海道支部優秀学生講演賞　　　　　　　　　　　　　　　
石狩川の感潮区域における大気の影響を踏まえた海水と淡水の相互作用
田中健人,山田朋人

May 2023, 令和四年度土木学会北海道支部技術研究発表会, 土木学会北海道支部優秀学生講演賞　　　　　　　　　　　　　　　
2007年台風9号と2019年台風19号が利根川・千曲川両流域を通過した際における地形性降雨の発生条件
松岡陽生,山田朋人

Oct. 2022, 水文・水資源学会／日本水文科学会 2022年度研究発表会, 優秀発表賞　　　　　　　　　　　　　　　
夏季の北海道とその周辺域における豪雨の抽出とその時空間特性
大屋祐太;山田朋人

Oct. 2022, 水文・水資源学会/日本水文科学会, 水文・水資源学会/日本水文科学会2022年度研究発表会における優秀発表賞　　　　　　　　　　　　　　　
夏季の北海道とその周辺域における豪雨の抽出とその時空間特性
大屋祐太;山田朋人

Sep. 2022, 第30回地球環境シンポジウム, 地球環境優秀講演賞　　　　　　　　　　　　　　　
気候予測データに基づく災害シナリオ作成 ～自治体災害支援システムIDR4Mを活用した避難情報の発令判断支援に向けて～
植村郁彦,鈴⽊章弘,⽯原道秀,⽶⽥駿星,星野剛,⼭本太郎,⼭⽥朋⼈

Sep. 2022, 第30回地球環境シンポジウム, 地球環境シンポジウム優秀ポスター賞　　　　　　　　　　　　　　　
気候予測データベースを活用した自治体の避難判断支援のための防災研修
鈴木章弘;植村郁彦;星野剛;米田駿星;山本太郎;橋本慎一;山田朋人

Sep. 2022, 土木学会, ポスター発表賞　　　　　　　　　　　　　　　
気候予測データベースを活用した自治体の避難判断支援のための防災研修
鈴木章弘;植村郁彦;星野剛;米田駿星;山本太郎;橋本慎一;山田朋人

Aug. 2022, 第30回地球環境シンポジウム, 地球環境優秀講演賞　　　　　　　　　　　　　　　
内外水同時解析を用いた浸水特性の分析
米田駿星;佐藤誠;江口陽祐;山田朋人

Jul. 2021, 日本気象学会北海道支部, 北海道支部発表賞　　　　　　　　　　　　　　　
北海道周辺域で線状降水帯が発生しやすい準季節平均場の将来変化
大屋 祐太;山田朋人

Jun. 2021, 2020年度河川技術論文賞　　　　　　　　　　　　　　　
気候変動予測情報を用いた極値水文量の統計的推定
清水啓太,山田正,山田朋人

May 2021, 土木学会北海道支部, 令和二年度土木学会北海道支部優秀学生講演賞　　　　　　　　　　　　　　　
降雨流出現象の不確実性に関する研究
青木一眞;山田朋人;成岱蔚

May 2021, 土木学会北海道支部, 令和二年度土木学会北海道支部優秀学生講演賞　　　　　　　　　　　　　　　
気象要素を用いる客観手法による梅雨前線の季節進行と年々変動
宮本真希;山田朋人

May 2021, 土木学会北海道支部, 令和二年度土木学会北海道支部優秀学生講演賞　　　　　　　　　　　　　　　
厚真川小流域における崩壊斜面からの流出土砂量の観測
宮崎功太郎;星野剛;山田朋人;橋場雅弘

May 2019, 土木学会北海道支部, 平成30年度土木学会北海道支部優秀学生講演賞　　　　　　　　　　　　　　　
無次元数を用いた十勝川集水域における豪雨の地形依存性評価
竹原由;山田朋人

Nov. 2018, 土木学会水工学委員会, 平成30年度 土木学会水工学論文奨励賞　　　　　　　　　　　　　　　
確率限界法検定に基づく確率分布モデルの信頼区間を導入した新しい水文頻度解析手法
清水啓太;山田朋人;山田 正

Jun. 2018, 2018年度河川技術に関するシンポジウム, 2018年河川技術に関するシンポジウム優秀発表者賞　　　　　　　　　　　　　　　
北海道における気候変動に伴う洪水外力の変化
山田朋人

2018, Japan Society of Civil Engineers, 2018年度河川技術論文賞受賞　　　　　　　　　　　　　　　
北海道における気候変動に伴う洪水リスクの変化
山田朋人;星野剛;舛屋繁和;植村郁彦;吉田隆年;大村宣明;山本太郎;千葉学;戸村翔;時岡真治;佐々木博文;濱田悠貴;中津川誠

Sep. 2017, 第25回地球環境シンポジウム, 第25回地球環境シンポジウム優秀ポスター賞　　　　　　　　　　　　　　　
確率限界法検定に基づく確率水文量の信頼区間に関する研究
清水啓太,山田朋人,山田 正

Dec. 2016, 土木学会応用力学委員会, 応用力学シンポジウムポスター賞　　　　　　　　　　　　　　　
北西太平洋を通過する爆弾低気圧と台風の比較
北野慈和;山田朋人

Sep. 2016, 土木学会地球環境委員会, 平成28年度地球環境論文奨励賞　　　　　　　　　　　　　　　
底面の加熱および冷却を伴う回転水槽実験による傾圧不安定波の再現
一瀬輪子, 北野慈和, 山田朋人, 渡部靖憲, 泉典洋

Jan. 2016, 土木学会北海道支部, 第56回土木学会北海道支部優秀学生講演賞　　　　　　　　　　　　　　　
大陸スケールにおける消雪日の空間分布および年々特性
布川 敦士;山田 朋人

Sep. 2015, 土木学会, 平成27年度第23回地球環境シンポジウム優秀ポスター賞　　　　　　　　　　　　　　　
ディスドロメータを用いた飛沫粒径分布の風速及び高度依存性
岡地寛季;山田朋人;渡部靖憲;猿渡亜由未;大塚 淳一;馬場 康之;水谷 英朗;久保 輝広;二宮 順一;内山 雄介;森 信人

Apr. 2015, 土木学会北海道支部, 平成26年度優秀学生講演賞　　　　　　　　　　　　　　　
CMIP5マルチモデルにおけるブロッキング発生頻度と極端現象の変遷
北野慈和;山田朋人

Apr. 2014, 土木学会北海道支部, 平成25年度土木学会北海道支部優秀学生講演賞　　　　　　　　　　　　　　　
MTSAT近赤外放射情報を用いた夏季のチャオプラヤ川流域における雲の日内特性
渡部大和;山田朋人

Apr. 2013, 土木学会北海道支部令和二年度年次技術研究発表会, 平成23年度土木学会北海道支部優秀学生講演賞　　　　　　　　　　　　　　　
夏季における石狩〜苫小牧館の海陸風循環
福島大輝;山田朋人

Apr. 2013, 土木学会北海道支部, 土木学会北海道支部優秀学生講演賞　　　　　　　　　　　　　　　
密度界面に発生するship waveの物理機構
北野慈和;山田朋人;泉典洋

Regional Characteristics of shape and stagnation of rainfall in Japan using Radar/Raingauge Analyzed Precipitation product
Yuta Ohya, Tomohito J. Yamada
Proceedings of IAHS, 386, 333, 338, Copernicus GmbH, 13 Aug. 2024
Scientific journal, Abstract. Recently, floods and sediment disasters caused by line-shaped rainbands (LRBs) have increased in frequency following events such as the torrential rainfall around Tokyo of September 2015, which flooded the Kinu River, Japan. During this event, the shape of the rainfall area matched the topology of the river basin, causing water levels to rise rapidly and resulting in a serious disaster. Therefore, the shape and duration of heavy rainfall patterns are critical factors that must be considered for flood prevention. In this study, we examined features of LRBs in river basins across Japan using long-term radar raingauge data, and investigated relationships between rainfall intensity, shape, duration, and quantity.

Meteorological characteristics of line-shaped rainbands in northern Japan and its surrounding seas under climate change
Yuta Ohya, Tomohito J. Yamada
Journal of Hydroinformatics, IWA Publishing, 30 Jan. 2024
Scientific journal, Abstract

In recent years, line-shaped rainbands (LRBs) have increased in Hokkaido, Japan. LRBs caused several flood disasters historically, thus the meteorological patterns that cause them need to be investigated. This study aimed to understand statistically the relationship between LRBs and weather patterns during the summer months under climate change conditions. Our study investigates the link between LRBs and meteorological patterns in Hokkaido during July and August, using historical and climate prediction models. With a 2°/4° global temperature rise, LRB occurrences in this region increase by approximately 1.51/2.07 times. The highest occurrences of LRBs correlate with increased water vapor flux from the south and positive pressure anomalies over the Pacific Ocean. Three main meteorological patterns contribute significantly to LRBs: (1) a nearby low-pressure system, (2) a strengthening Pacific High frontal pattern, and (3) approaching or landing typhoons in Hokkaido. These patterns double the LRB occurrence probability, a trait observed across past and projected climates (+2K and +4K experiments). These are important insights for future flood risk management.

FLOOD INUNDATION ANALYSIS IN LOW-LYING RIVER BASIN USING DIFFERENT DIGITTAL ELEVATION MODEL
Kei KOURA, Naoki KOYAMA, Tadashi YAMADA, Tomohito J. YAMADA
Japanese Journal of JSCE, 80, 16, n/a, n/a, Japan Society of Civil Engineers, 2024
Scientific journal

冬季石狩川下流域における筋状雲の抽出と雲域・非雲域下におけるGPS可降水量の定量的評価
Dan HASHIMOTO, Maki MIYAMOTO, Yuta OHYA, Tomohito J. YAMADA
Japanese Journal of JSCE, 80, 16, n/a, n/a, Japan Society of Civil Engineers, 2024
Scientific journal

Regional characteristics of contribution of atmospheric fronts to heavy rainfall in boreal summer over Japan, Northwestern Pacific
Maki Miyamoto, Tomohito J. Yamada
Hydrological Research Letters, 18, 1, 28, 34, Japan Society of Hydrology and Water Resources, 2024
Scientific journal

Spatiotemporal classification of heavy rainfall patterns to characterize hydrographs in a high-resolution ensemble climate dataset
Tsuyoshi Hoshino, Tomohito J. Yamada
Journal of Hydrology, 617, 128910, 128910, Elsevier BV, Feb. 2023
Scientific journal

Comparison of Meteorological Fields and Distribution of Rainfall in Typhoon Lionrock(2016) and Typhoon Phyllis(1981)
Maki MIYAMOTO, Tomohito J. YAMADA
Japanese Journal of JSCE, 79, 27, n/a, n/a, Japan Society of Civil Engineers, 2023
Scientific journal

Analysis of planetary boundary layer feedbacks on the multiple equilibria of the continental water cycle
Abhinav Dengri, Tomohito Yamada
IOP Conference Series: Earth and Environmental Science, 1136, 1, 012012, 012012, IOP Publishing, 01 Jan. 2023
Scientific journal, Abstract

A simple soil-atmosphere interaction model is developed to study the bimodal distribution of soil moisture in regions where there is feedback between precipitation and soil moisture. Our study includes planetary boundary layer (PBL) feedback in the coupled analytical soil-atmosphere interaction model with a varying PBL height and entrainment from the free atmosphere. This study aims to reveal the dominant PBL feedbacks that impact the occurrence of soil moisture bimodality by comparing the evolution of prognostic variables for a detailed PBL scheme (with varying PBL height and entrainment of heat and moisture from the free atmosphere) with the simple PBL scheme (with fixed PBL height and no entrainment). This study has shown the existence of multiple equilibria in the continental water balance for both detailed PBL and simple PBL schemes when the model is integrated for different initial soil moisture up to equilibria. Although both with and without PBL feedback, the results are in qualitative agreement; the soil moisture initialization to realize multiple equilibria of a detailed PBL scheme is larger than the simple PBL scheme. Although the direct quantitative comparison with observation is clearly limited in the simple model, it also demonstrates how the non-linear dynamics of the coupled soil-atmosphere system may be expected to occur in observations.

Changes in sediment erosion rate in the Azuma River basin after the Hokkaido eastern Iburi earthquake in 2018
Kotaro Miyazaki, Tsuyoshi Hoshino, Keita Shimizu, Sourabh Shrivastava, Tomohito J Yamada
IOP Conference Series: Earth and Environmental Science, 1136, 1, 012027, 012027, IOP Publishing, 01 Jan. 2023
Scientific journal, Abstract

The Hokkaido Eastern Iburi earthquake in 2018 induced the largest landslide over the Azuma River basin in Hokkaido, the north island of Japan. This study estimated the sediment erosion rate over the Azuma River basin using the universal soil loss equation (USLE) for the pre- and post-earthquake conditions. The results showed that the potential sediment erosion rate from the entire basin increased by 8–29 times more than the pre-earthquake condition. The primary cause of the increase in sediment erosion rate was deforestation due to the landslide, which generated 13% of the bare land area in the entire basin. In addition, the influence of interannual variability of rainfall on sediment erosion rate was calculated from observed rainfall data. As a result, the minimum annual sediment erosion rate after the earthquake exceeded the maximum before the earthquake, indicating that the post-earthquake sediment erosion rate is substantially higher than the pre-earthquake rate. These findings suggest that in order to assess the sediment erosion risk over the Azuma River basin, it is necessary to predict and monitor the vegetation recovery, considering the interannual variability of rainfall.

Characteristics of line-shaped rainbands regarding duration, shape, and rainfall intensity in northern Japan using the Radar/Raingauge-Analyzed Precipitation Product
Yuta Ohya, Tomohito J Yamada
IOP Conference Series: Earth and Environmental Science, 1136, 1, 012025, 012025, IOP Publishing, 01 Jan. 2023
Scientific journal, Abstract

Line-shaped rainbands (LRBs), including Mesoscale Convective Systems (MCSs), stagnate on river basins and cause floods and landslides. Moreover, the frequency of LRBs is increasing around Hokkaido a part of northern Japan. Due to the complexity of the three-dimensional structures found in LRBs, some research dealt with two-dimensional observation data to identify them for the sake of simplicity. In previous studies, several methods to widely identify LRBs from radar rainfall data in terms of rainfall intensity, shape of rainfall area, and duration have been proposed. However, using the nationally consistent definition, the number of LRBs occurring in this region would be evaluated as very few due to the little rainfall climatology of this area. In this study, based on the previous studies, we adjust many combinations of threshold values, such as rainfall intensity, aspect ratio, and time duration in order to verify of validity the LRBs that occurred in northern Japan. The authors visually identified the six LRBs that caused the disaster and showed thresholds at which they were mechanically extractable by a computer program. The combination of thresholds that included at least six of those disaster-scale cases was “a rainfall area defined by a closed curve with a previous 3-hour rainfall of 40 mm or more, stagnating for 2 hours or more (covering 40% or more of its area), and with a maximum aspect ratio of 2.5 or more.”

Points of consideration on identification of the atmospheric fronts depicted on weather charts
Maki Miyamoto, Tomohito J. Yamada
IOP Conference Series: Earth and Environmental Science, 1136, 1, 012023, 012023, IOP Publishing, 01 Jan. 2023
Scientific journal, Abstract

Atmospheric fronts play an important role on the day-to-day variation of rainfall in Japan, North-western Pacific. They are defined as a discrepancy of air density and have been depicted on surface weather charts for more than 100 years by Japan Meteorological Agency (JMA). This study develops an approach to detect fronts from the charts published from 1978 to 2020 and investigates how detected fronts could be utilized. The fronts which are depicted on the charts might have a diverse physical characteristic in each age. One of factors is a difference in how to represent fronts. The difference also prevents from detecting fronts under a certain accuracy. Previous study demonstrates detecting fronts based on the color available from the charts. However, this approach is applicable for weather charts published after 2000 by JMA. This paper describes consideration points for a unified detection of fronts from the charts for 43 years in detail. Furthermore, we compare fronts detected by several methods and discuss a spatial scale in which their differences could be neglected.

Future Changes in Tropical and Extratropical Cyclones Affecting Hokkaido and Their Related Precipitation Based on Large-Ensemble Climate Simulations
Sho Kawazoe, Masaru Inatsu, Tomohito J. Yamada, Tsuyoshi Hoshino
Journal of Applied Meteorology and Climatology, American Meteorological Society, 22 Dec. 2022
Scientific journal, Abstract

This study investigates the impact of future climate warming on tropical (TC) and extratropical cyclones (ETC) using the database for Policy Decision-making for Future climate change (d4PDF) large ensemble simulations. Cyclone tracking was performed using the Neighbor Enclosed Area Tracking algorithm (NEAT), and TC and ETCs were identified over the western North Pacific (WNP). For cyclone frequency, it was revealed that while a slight underestimation of the total number of TCs and ETCs in both the WNP and near Hokkaido, Japan, exists, the d4PDF reproduced the spatial distribution of both TC and ETC tracks well compared to observations/reanalysis. The 4-K warming scenarios derived from six different sea surface temperature warming patterns showed robust decreases in TC frequency in the tropical WNP and a slight reduction in ETCs near Japan. Next, precipitation characteristics for TCs or ETCs in the vicinity of Hokkaido were examined using 5 km-mesh regional climate ensemble simulations. Four representative cyclone locations near Hokkaido are identified using K-means clustering and revealed distinct precipitation characteristics between clusters, with higher TC-associated precipitation than ETC-associated precipitation and the heaviest precipitation in the southern portion of the prefecture. The 4-K warming scenarios revealed increased precipitation for all cyclone placements for both TCs and ETCs. Lastly, average cyclone intensity, translation speed, and size were examined. It was shown that TCs in future climates are more intense, propagate more slowly, and are smaller in terms of enclosed vorticity area as they approach Hokkaido. For ETCs, mean intensity does not change much, they travel slightly faster, and become smaller.

Land–sea thermal contrast associated with summer monsoon onset over the Chao Phraya River basin
Tomohito J. Yamada, Sourabh Shrivastava, Ryosuke Kato
Theoretical and Applied Climatology, 150, 1-2, 73, 83, Springer Science and Business Media LLC, Oct. 2022, [Peer-reviewed], [Lead author]
English, Scientific journal, Abstract

Earlier onset of the Southeast Asian summer monsoon (SAM) was observed over the Chao Phraya River basin in Thailand using Thai Meteorological Department-derived high-resolution merged rainfall data from 1981 to 2016. SAM variability depends on numerous local and global factors, including thermal conditions over the Bay of Bengal (BoB) and Tibetan Plateau (TbT). Despite tremendous past research efforts, the effect of thermal heat contrast on the SAM remains unclear. Using observational and reanalysis datasets, we found that the absolute value of total heat over the BoB was increasing. However, the interannual variability of total heat was greater over the TbT. Changes in surface temperature (± 1.5 °C), air thickness (± 20 m), and geopotential height over the TbT were associated with the timing of SAM onset. The results also suggested that significant changes in air thickness are driven by surface temperature differences over the TbT, while changes in the integrated apparent heat source and integrated apparent moisture sink of ± 100 W m⁻² resulted in anomalous convective activities over the BoB and mainland of the Indochina Peninsula in years of early and late SAM onset. At the intraseasonal timescale, Madden–Julian oscillation (MJO) was observed over the Indian Ocean and Western Hemisphere for 4–10 days in years of early SAM onset. The opposite situation was found for years of late SAM onset, with MJO located over the Western Pacific Ocean and Maritime Continent.

Particulate Matter Concentrations over South Korea: Impact of Meteorology and Other Pollutants
Shaik Allabakash, Sanghun Lim, Kyu-Soo Chong, Tomohito J. Yamada
Remote Sensing, 14, 19, 4849, 4849, MDPI AG, 28 Sep. 2022, [Peer-reviewed]
English, Scientific journal, Air pollution is a serious challenge in South Korea and worldwide, and negatively impacts human health and mortality rates. To assess air quality and the spatiotemporal characteristics of atmospheric particulate matter (PM), PM concentrations were compared with meteorological conditions and the concentrations of other airborne pollutants over South Korea from 2015 to 2020, using different linear and non-linear models such as linear regression, generalized additive, and multivariable linear regression models. The results showed that meteorological conditions played a significant role in the formation, transportation, and deposition of air pollutants. PM2.5 levels peaked in January, while PM10 levels peaked in April. Both were at their lowest levels in July. Further, PM2.5 was the highest during winter, followed by spring, autumn, and summer, whereas PM10 was the highest in spring followed by winter, autumn, and summer. PM concentrations were negatively correlated with temperature, relative humidity, and precipitation. Wind speed had an inverse relationship with air quality; zonal and vertical wind components were positively and negatively correlated with PM, respectively. Furthermore, CO, black carbon, SO2, and SO4 had a positive relationship with PM. The impact of transboundary air pollution on PM concentration in South Korea was also elucidated using air mass trajectories.

EVALUATION OF NON-STATIONARITY IN EXTREME PRECIPITATION TIME SERIES BASED ON PROBABILITY LIMIT METHOD
Takeshi KODAMA, Keita SHIMIZU, Tomohito J, YAMADA
河川技術論文集, 28, 343, 348, Jun. 2022, [Peer-reviewed]
Japanese, Symposium

日蘭共同研究「Flood Risk and Climate Change Hokkaido （北海道における氾濫リスクと気候変動）」最終報告書　　　　　　　　　　　　　　　
Bob Maaskant, Bas Kolen, Mark Hegnauer, 千葉学, 植村郁彦, 山田朋人
Feb. 2022

CHARCTERISTICS OF SYNOPTIC CONDITIONS DURING SUMMER SEASON ASSOCIATING EXTREME OCCURANCE OF LINE-SHAPED RAINBANDS AROUND HOKKAIDO USING LARGE ENSEMBLE DATA
Yuta OHYA, Maki MIYAMOTO, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 78, 2, I_43, I_48, Japan Society of Civil Engineers, 2022
Scientific journal

Global Warming Effect and Adaptation for a Flooding Event at Motsukisamu River in Sapporo
Yuka Kanamori, Masaru Inatsu, Ryoichi Tsurumaki, Naoki Matsuoka, Tsuyoshi Hoshino, Tomohito J. Yamada
SOLA, 18, 249, 253, Meteorological Society of Japan, 2022
Scientific journal

FEARURES OF OCCURRENCE OF LINEAR AND STAGNANT RAINFALL BANDS UNDER PAST AND FUTURE CLIMATE AROUND HOKKAIDO
OHYA Yuta, YAMADA Tomohito J.
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 78, 5, I_225, I_231, Japan Society of Civil Engineers, 2022
Japanese, Using observations and the Ensemble Climate Prediction Database (d4PDF), we analyzed the occurrence characteristics of linear and stagnant precipitation bands. In recent years, heavy rainfall disasters involving LRB have been frequent all over Japan, and the Japan Meteorological Agency defines a linear precipitation bands from the shape and stagnation time of precipitation zones of 80 mm/3h or more from the aspect of disaster prevention. In Hokkaido, however, several floods and landslides have occurred even with much lower precipitation than that. In this study, LRB are redefined for the Hokkaido region, and the frequency of occurrence, regional distribution, and model characteristics in past and present climates are shown through observations and application to the d4PDF.

A RELATIONSHIP OF ATMOSPHERIC FRONTS AND RAINFALL IN WESTERN JAPAN IN THE RAINY SEASON
MIYAMOTO Maki, YAMADA Tomohito J.
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 78, 5, I_151, I_156, Japan Society of Civil Engineers, 2022
Japanese, In this study, a method for extracting fronts from weather maps treated as weather information was developed and applied to 34 years of weather maps. The front can now be treated as grid data, and it is shown that rainfall within 100 km around the front accounts for more than 30% of the rainfall in the Kyushu region in June and July. Furthermore, it was found that the spatial mean rainfall over the area passed by the front as it moved meridionally over the Kyushu region reached a maximum when the front moved about 300 kilometers. The weather patterns suggest that the north-south movement of the front is affected by moving depression with fronts, the approach of a typhoon or tropical cyclone, and an enhancement of an anticyclone.

ESTIMATION OF EQUATION FOR DROP SIZE DISTRIBUTION OF SEA SPRAY UNDER SEVER WIND CONDITIONS
OKACHI Hiroki, YAMADA Tomohito J.
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 78, 5, I_171, I_177, Japan Society of Civil Engineers, 2022
Japanese, Drop size distribution of sea spray generated from wave breakings can be a confounding factor for rainfall observations at sea, and has significance as a sea-salt particle that causes salt damage and rainfall inland. In this study, field observations of sea spray were conducted using a disdrometer, and drop size distribution equation as a function of wind speed was proposed. The proposed equation enables the estimation of the amount of sea spray that can be mixed during rainfall observations and the estimation of the amount of sea spray that are the source of sea salt particles that cause salt damage and cause rainfall.

Analysis of soil moisture and precipitation bimodal distribution for boreal summer using satellite data over northern India
Dengri Abhinav, Yamada Tomohito
水文・水資源学会研究発表会要旨集, 35, 257, 水文・水資源学会, 2022
Japanese, We study bimodal distribution for soil moisture and precipitation using satellite dataset over the northern Indian region. Strong soil moisture bimodality is present over northern india which is caused by clear transition from dry to wet season.

最近の気候変動予測研究と今後の先端的な気候変動予測に向けて
高薮 出, 辻野 博之, 村田 昭彦, 川瀬 宏明, 仲江川 敏之, 山田 朋人, 山崎 剛, 石川 洋一, 坪木 和久
水文・水資源学会研究発表会要旨集, 35, 113, 水文・水資源学会, 2022
Japanese, 将来の水文・水資源の様相を評価するためには、将来気候変動の予測が必要不可欠である。気候変動予測シミュレーション技術の高度化等による将来予測の不確実性の低減や、気候変動メカニズムの解明に関する研究開発、気候予測データの高精度化等からその利活用までを想定した研究開発を一体的に推進することで、気候変動対策に活用される科学的根拠を創出・提供することを目的とした、文部科学省「気候変動予測先端研究プログラム」が開始された。このプログラムの下、日本域における気候変動予測の高度化を目指して（領域課題３：「日本域における気候変動の高度化」）、1：日本域気候変動の予測システム開発とメカニズム解明、2：極端現象のメカニズム解明による地域・流域に応じた適応策推進に資する気候変動予測情報の創出、3：海外の脆弱地域における高精度気候予測データセットの創出に、我々は取り組んでいる。また、水文・水資源分野を始めとして、多様なユーザーとの対話を通して、気候変動予測の共通認識の醸成を目指している。これらの研究目標の基盤となる研究を、すでに文部科学省「統合的気候モデル高度化研究プログラム」等で実施してきた。その成果の一例として、大気海洋相互作用を表現可能な日本域気候変動予測システム(Time Sequential Experiments with Coupled model; TSE-C）の開発や、近年洪水事例が多発している要因がこれまでの温暖化によるのか、それ以外の要因かを明らかにするイベントアトリビューション研究が挙げられる。気候変動予測の現在地点と今後の計画を紹介し、議論の端緒としたい。

横堤の規模の違いによる河道および遊水池の遊水機能の感度分析
石原 道秀, 山田 朋人
水文・水資源学会研究発表会要旨集, 35, 285, 水文・水資源学会, 2022
Japanese, 気候変動の影響により水害の更なる頻発・激甚化が懸念される中，流域治水関連法が令和3年11月に施行された．流域治水のおける治水計画では，流域を集水域・河川区域・氾濫域の3つから捉え，1)氾濫をできるだけ防ぐ・減らす対策，2)被害対象を減少させるための対策，3)被害の軽減，早期復旧・復興のための対策，をハード・ソフト一体で多層的に進められている¹⁾．これらの対策の具体のうち，本研究と関連するものは遊水池整備である． 遊水池は，洪水を一時的に貯めることで下流に洪水が一気に流れ出すことを防ぐ役割を持つ．遊水池が効果を発揮した一例として，釧路川および釧路湿原における2016年8月の大雨に伴う出水がある．釧路川および釧路湿原では，湿原が持つ遊水機能を高めるために，湿原の下流端に横堤が設置されている．これにより2016年8月の大雨では，湿原に約2.1千万m3の水量（東京ドーム約17杯分）を貯留し，横堤下流側の水位が低減したことが試算されている²⁾．将来予測の不確実性を考慮した上で流域治水を実施するには，外力規模ごとの遊水池の効果の定量化が必要となるはずである．そこで本研究では，ある外力に対する横堤の規模の違いから遊水機能がどう変化するのか把握することを目的に，釧路川および釧路湿原を模した簡易的な数値実験による感度分析を実施した．

泥炭堆積モデルの感度分析による泥炭地の特性を表すパラメータの推定
内藤 大梧, 山田 朋人
水文・水資源学会研究発表会要旨集, 35, 245, 水文・水資源学会, 2022
Japanese, 泥炭地は地域特有の植生と高い地下水位によって成立しており，急速な温暖化の進行や人為的な地域水文環境の変動によって大きな影響を受ける可能性がある．一方で泥炭地の経年変化を数理モデル化した「泥炭堆積モデル(Peat Accumulation model）」においてその目的の多くは気候変動に対する炭素の固定量の変化の算出であり，透水係数をはじめとする各係数や堆積量などについて実際の泥炭地での観測との比較が行われた例は少ない．そのため，泥炭堆積モデルにおいて計算された各係数の値が，実際の値と一致しない可能性がある． ここでは，泥炭堆積モデルの最新モデルの一つであるMPeatについて感度分析を行い，どのようなパラメータがモデルの計算結果により大きな影響を及ぼすのか，観測結果と照らし合わせる必要があるかを明らかにした． 泥炭堆積モデルMPeatの感度分析の結果，泥炭地の半径や透水係数のパラメータ，ヤング率のパラメータ，植物の生産量がモデルの結果に特に大きな影響を与えていることが確認された．泥炭堆積モデルによる堆積予測を行う際には，対象地域の泥炭の特性を観測などにより十分理解する必要があると思われる．

天気図に示された前線の高空間解像度グリッドデータによる表現とその活用
宮本 真希, 山田 朋人
水文・水資源学会研究発表会要旨集, 35, 249, 水文・水資源学会, 2022
Japanese, 日本が位置する中緯度帯において，年間降水量のうち約7割は前線による降水である．前線に伴う豪雨災害は広範囲かつ甚大であり，例えば令和2年7月豪雨や平成30年7月豪雨では西日本を中心に，昭和56年水害では北海道の道央において被害が拡大した．これらは各地域の代表的な豪雨災害であるため，日本全国を対象として，前線に伴い生じる豪雨を議論する必要がある．天気図に示された前線はUtsumi et al. (2014)が提案した手法により1度格子データとして利用可能である．本研究では，より空間解像度の高いグリッドデータを作成し，前線データの活用について議論する．

対象期間は1978年から2020年の6月から10月とした．既往手法に加えて，本研究では，高解像度グリッドデータを作成するために物体認識および形状認識により三角および半円を取り除き，線として前線を表した．さらに，1999年以前の天気図においては前線が黒で描かれており，そのままでは色に基づく前線抽出が行えないため，目視による判断で前線を色付けして43年間の前線データを作成した． 作成した前線データは，前線の幅は約100kmであると仮定した場合，どの抽出方法においても概ね同質である．空間解像度を0.1度した場合においても抽出方法による前線の位置の違いは数十kmにとどまるため，天気図スケールより小さい空間スケールに対しても有用であると推測される．

湖及びダム湖における鉛直水温分布の季節変動について
青木 一眞, 山田 朋人
水文・水資源学会研究発表会要旨集, 35, 197, 水文・水資源学会, 2022
Japanese, 湖の水温は水面の熱収支の問題であり、季節や、それぞれのダム湖が位置する気候によって湖中の水温構造は変化する。水温構造の変化や、それに伴う水質の変化は、湖の生態系や、農業、工業、生活用水などの利水に影響を及ぼす。本研究では全国の湖やダム湖における水温構造、水質変化、全層循環の発生の有無の詳細な検討や、それらの将来における変化を示すことを目標とし、本稿ではその第一段階として十勝ダムにおける東大雪湖について鉛直1次元の水温解析モデルを適用した結果を示す。

暴風雨時における海面付近に分布する飛沫濃度及び水平風速の推定手法
岡地 寛季, 山田 朋人
水文・水資源学会研究発表会要旨集, 35, 43, 水文・水資源学会, 2022
Japanese, 海面抵抗の大きさの指標となる海面抵抗係数は従来風速に対して単調増加として扱われるが，Powell et al. (2003)は暴風時に減少することを観測より示した．近年はある風速を超えると一定値となることが示唆されている．しかし，海面近傍の飛沫の質量密度や水平風速は暴風雨下かつ混相流としての基礎的な物理量であるが，極端現象が生起することが稀有であることや暴風雨下での観測が困難であるという背景を有する．そこで本研究は極端現象下の海面近傍の領域を対象にレーダ観測を実施し，飛沫の質量密度及び水平風速の推定手法を提案する．

夏季の北海道とその周辺域における豪雨の抽出とその時空間特性
大屋 祐太, 山田 朋人
水文・水資源学会研究発表会要旨集, 35, 253, 水文・水資源学会, 2022
Japanese, 本研究は，北海道とその周辺域の観測データおよび大量アンサンブルデータから同地域における降雨量が集中する7-9月に発生した線状かつ停滞性を有する豪雨を客観的に抽出した．特に同地域は日本海・太平洋・オホーツク海の特性の異なる海に囲われ，大雪山系・日高山脈の地形によるエリアごとの気候特性を有するため，こうした特徴に注目し，議論を行う．

気候変動を考慮した流域全体を俯瞰した水害リスクの考え方　　　　　　　　　　　　　　　
山田朋人
日本不動産学会誌, 36, 1(140), 2022, [Lead author]
Japanese, Scientific journal

日蘭共同研究「Flood Risk and Climate Change Hokkaido （北海道における氾濫リスクと気候変動）」詳細報告書１　　　　　　　　　　　　　　　
星野剛, Mark, H, 清水啓太, 山田朋人
2022

Grand Ethiopian Renaissance Dam and hydrologic hegemony over Abbay Basin
Tesfa Gebrie Andualem, Mulatu Kassa, Girum Getachew Demeke, Guna Hewa, Imran Ahmed Dar, Quoc Bao Pham, Tomohito J. Yamada
Sustainable Water Resources Management, 7, 6, Springer Science and Business Media LLC, Dec. 2021, [Peer-reviewed]
Scientific journal

Probability assessment of slope instability in seasonally cold regions under climate change
Yulong Zhu, Tatsuya Ishikawa, Tomohito J. Yamada, Srikrishnan Siva Subramanian
Journal of Infrastructure Preservation and Resilience, 2, 1, Springer Science and Business Media LLC, Dec. 2021, [Peer-reviewed]
Scientific journal, To semi-quantitatively assess the effects of climate change on the slope failures, this paper proposes an effective approach for evaluating the influences of climate change on slope stability in seasonally cold regions. To discuss climate change, this study firstly analyzes the trend of the two main climate factors (precipitation and air temperature) based on the regression analysis results of the meteorological monitoring data during the past 120 years in different scales (e.g., world, country (Japan), and city (Sapporo)), and the downscaled outputs of three different regional atmospheric models (RAMs) with lateral boundary conditions from three different general circulation models (GCMs). Next, to discuss the effects of different climate factors (air temperature, precipitation, etc.) and to determine the key climate factors on the slope instability, a slope stability assessment approach for evaluating the effects of climate changes on slope instability is proposed through the water content simulation and slope stability analysis with considering freeze-thaw action. Finally, to check the effectiveness of the above assessment approach, assessment of instability of an actual highway embankment slope with the local layer geometry is done by applying the past and predicted future climate data. The results indicate that affected by global warming, the air temperature rise in some cold cities is more serious. The climate changes (especially the increase in precipitation) in the future will increase the infiltration during the Spring season. It will lengthen the time that the highway slope is in an unstable state due to high volumetric water content, causing the occurrence of slope failures will be more concentrated in April. While during the Ssummer-Autumn period, the time domain of its occurrence will become wider.

Construction of a High-resolution Ensemble Climate Dataset for Duture Projection of Flood Risk in the Kanto Region　　　　　　　　　　　　　　　
山田朋人, 星野剛, 清水啓太, 成岱蔚
Annual Report of the Earth Simulator April 2020 - February 2021, Oct. 2021

Assessment of Future Flood Risks and Its Cause using Dynamical Downscaling　　　　　　　　　　　　　　　
星野剛, 山田朋人
Annual Report of the Earth Simulator April 2020 - February 2021, Oct. 2021

Using a massive high‐resolution ensemble climate data set to examine dynamic and thermodynamic aspects of heavy precipitation change
Tomohito J. Yamada, Tsuyoshi Hoshino, Akihiro Suzuki
Atmospheric Science Letters, 22, 8, Wiley, 04 Aug. 2021, [Peer-reviewed]
Scientific journal

Flood Inundation Assessment in the Low-Lying River Basin Considering Extreme Rainfall Impacts and Topographic Vulnerability
Thanh Thu Nguyen, Makoto Nakatsugawa, Tomohito J. Yamada, Tsuyoshi Hoshino
Water, 13, 7, 896, 896, MDPI AG, 25 Mar. 2021, [Peer-reviewed]
Scientific journal, This study aims to evaluate the change in flood inundation in the Chitose River basin (CRB), a tributary of the Ishikari River, considering the extreme rainfall impacts and topographic vulnerability. The changing impacts were assessed using a large-ensemble rainfall dataset with a high resolution of 5 km (d4PDF) as input data for the rainfall–runoff–inundation (RRI) model. Additionally, the prediction of time differences between the peak discharge in the Chitose River and peak water levels at the confluence point intersecting the Ishikari River were improved compared to the previous study. Results indicate that due to climatic changes, extreme river floods are expected to increase by 21–24% in the Ishikari River basin (IRB), while flood inundation is expected to be severe and higher in the CRB, with increases of 24.5, 46.5, and 13.8% for the inundation area, inundation volume, and peak inundation depth, respectively. Flood inundation is likely to occur in the CRB downstream area with a frequency of 90–100%. Additionally, the inundation duration is expected to increase by 5–10 h here. Moreover, the short time difference (0–10 h) is predicted to increase significantly in the CRB. This study provides useful information for policymakers to mitigate flood damage in vulnerable areas.

A review of climate-change impact and adaptation studies for the water sector in Thailand
Masashi Kiguchi, Kumiko Takata, Naota Hanasaki, Boonlert Archevarahuprok, Adisorn Champathong, Eiji Ikoma, Chaiporn Jaikaeo, Sudsaisin Kaewrueng, Shinjiro Kanae, So Kazama, Koichiro Kuraji, Kyoko Matsumoto, Shinichiro Nakamura, Dzung Nguyen-Le, Keigo Noda, Napaporn Piamsa-Nga, Mongkol Raksapatcharawong, Prem Rangsiwanichpong, Sompratana Ritphring, Hiroaki Shirakawa, Chatuphorn Somphong, Mallika Srisutham, Desell Suanburi, Weerakaset Suanpaga, Taichi Tebakari, Yongyut Trisurat, Keiko Udo, Sanit Wongsa, Tomohito Yamada, Koshi Yoshida, Thanya Kiatiwat, Taikan Oki
Environmental Research Letters, 16, 2, 023004, 023004, IOP Publishing, 01 Feb. 2021, [Peer-reviewed]
English, Scientific journal, Thailand plays a central economic and policy-making role in Southeast Asia. Although climate change adaptation is being mainstreamed in Thailand, a well-organized overview of the impacts of climate change and potential adaptation measures has been unavailable to date. Here we present a comprehensive review of climate-change impact studies that focused on the Thai water sector, based on a literature review of six sub-sectors: riverine hydrology, sediment erosion, coastal erosion, forest hydrology, agricultural hydrology, and urban hydrology. Our review examined the long-term availability of observational data, historical changes, projected changes in key variables, and the availability of economic assessments and their implications for adaptation actions. Although some basic hydrometeorological variables have been well monitored, specific historical changes due to climate change have seldom been detected. Furthermore, although numerous future projections have been proposed, the likely changes due to climate change remain unclear due to a general lack of systematic multi-model and multi-scenario assessments and limited spatiotemporal coverage of the study area. Several gaps in the research were identified, and ten research recommendations are presented. While the information contained herein contributes to state-of-the-art knowledge on the impact of climate change on the water sector in Thailand, it will also benefit other countries on the Indochina Peninsula with a similar climate.

AN INTERANNUAL VARIATION OF ATMOSPHERIC FRONTS AND SURROUNDING ATMOSPHERIC CONDITIONS FROM MAY TO JULY DURING RAINY SEASON IN SOUTH-WESTERN JAPAN
Maki MIYAMOTO, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 77, 2, I_463, I_468, Japan Society of Civil Engineers, 2021
Scientific journal

内外水同時解析による浸水発生要因に着目した浸水被害特性の評価手法の提案　　　　　　　　　　　　　　　
米田駿星, 佐藤誠, 川村育男, 山田朋人
河川技術論文集, 27, 517, 522, 2021, [Peer-reviewed]

流域治水の検討に資するオランダの遊水地化事業に関する調査報告　　　　　　　　　　　　　　　
戸村翔, 千葉学, 山本太郎, 武田淳史, 植村郁彦, 舛屋繁和, 大村宣明, 吉田隆年, 星野剛, 山田朋人, 中津川誠
河川技術論文集, 27, 591, 596, 2021, [Peer-reviewed]

d4PDFを活用した発電専用ダムによる洪水被害軽減運用手法の効果検証　　　　　　　　　　　　　　　
松本知士, 池田典之, 河田暢亮, 山田朋人, 中津川誠, 中北英一
河川技術論文集, 27, 637, 642, 2021, [Peer-reviewed]

風速シア無し・安定度一定条件のおろし風の水理学的表現の検討　　　　　　　　　　　　　　　
北野慈和, 山田朋人
土木学会論文集B1(水工学), 77, 1315, 1320, 2021, [Peer-reviewed]

アンサンブル気候データを用いた降雨強度-気温の関係の分析　　　　　　　　　　　　　　　
星野剛, 山田朋人
土木学会論文集B1(水工学), 77, 1267, 1272, 2021, [Peer-reviewed]

Analytical Land-vegetation-atmosphere Model to Study Soil Moisture Bimodality　　　　　　　　　　　　　　　
A. Dengri, T. J. Yamada
Journal of Japan Society of Civil Engineers, Ser. B1(Hydraulic Engineering), 77, 235, 240, 2021, [Peer-reviewed]

九州地方を対象とした梅雨期における前線および周辺環境場の年々特性　　　　　　　　　　　　　　　
宮本真希, 山田 朋人
土木学会論文集B1(水工学), 77, 463, 468, 2021, [Peer-reviewed]

情報理論を導入した確率降雨量の統合的将来予測　　　　　　　　　　　　　　　
清水啓太, 山田朋人
土木学会論文集B1(水工学), 77, 163, 168, 2021, [Peer-reviewed]

現代ポートフォリオ理論を用いた降雨時空間分布の不確実性を考慮した流域内各河川への効率的な投資比率について　　　　　　　　　　　　　　　
舛屋繁和, 千葉 学, 山田 朋人
土木学会論文集B1(水工学), 77, 1399, 1404, 2021, [Peer-reviewed]

PROPOSAL OF RAINFALL EVALUATION METHOD BASED ON COMPOUND PROBABILITY USED FOR METEOROLOGICAL ENSEMBLE DATA
Hayase YONEDA, Ikuo KAWAMURA, Shigeo OKAWA, Makoto SATO, Tomohito YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 77, 2, I_1285, I_1290, Japan Society of Civil Engineers, 2021, [Peer-reviewed]
Japanese, Scientific journal

Hydrological frequency analysis of large-ensemble climate simulation data using control density as a statistical control
Daiwei Cheng, Keita Shimizu, Tomohito J. Yamada
Hydrological Research Letters, 15, 4, 84, 91, Japan Society of Hydrology and Water Resources, 2021, [Peer-reviewed]
Scientific journal

Characteristics of Rain and Sea Spray Droplet Size Distribution at a Marine Tower
Hiroki Okachi, Tomohito J. Yamada, Yasuyuki Baba, Teruhiro Kubo
Atmosphere, 11, 11, 1210, 1210, MDPI AG, 09 Nov. 2020, [Peer-reviewed]
Scientific journal, The effects of sea spray on open-ocean rainfall measurements-the drop size distribution (DSD) and rainfall intensities-were studied using a state-of-the-art optical disdrometer. The number of rain droplets less than 1 mm in diameter is affected by several factors, including the type of rainfall and seasonality. Over the ocean, small rain and large sea spray droplets co-exist in the same diameter size class (0.072 to 1000 mm); hence, sea spray creates uncertainty when seeking to characterize the drop size distribution (DSD) of rain droplets over the ocean. We measured droplet sizes at a marine tower using a state-of-the-art optical disdrometer, a tipping-bucket rain gauge, a wind anemometer, and a time-lapse camera, over a period that included typhoon Krosa of 2019. The number of rain droplets of diameter less than 1 mm increased monotonically as the horizontal wind speed became stronger. Thus, the shape parameter μ of the Ulbrich distribution decreased. This decreasing trend can be recognized as an increase in sea spray. During no-rainfall hours (indicated by rain gauges on the ocean tower and nearby land), sea spray DSDs were obtained at various horizontal wind speeds. Furthermore, the proportions of sea spray to rainfall at different rainfall intensities and horizontal wind speeds were determined; at a horizontal wind speed of 16 to 20 m s−1, the average sea spray proportions were 82.7%, 19.1%, and 5.3% during total rainfall periods of 2.1 mm h−1, 8.9 mm h−1, and 32.1 mm h−1, respectively. Representation of sea spray DSDs, as well as rainfall DSDs, is a key element of calculating real rainfall intensities over the open ocean.

Introduction of Confidence Interval Based on Probability Limit Method Test into Non-Stationary Hydrological Frequency Analysis
Keita Shimizu, Tadashi Yamada, Tomohito J. Yamada
Water, 12, 10, 2727, 2727, MDPI AG, 29 Sep. 2020, [Peer-reviewed]
Scientific journal, Nonstationarity in hydrological variables has been identified throughout Japan in recent years. As a result, the reliability of designs derived from using method based on the assumption of stationary might deteriorate. Non-stationary hydrological frequency analysis is among the measures to counter this possibility. Using this method, time variations in the probable hydrological quantity can be estimated using a non-stationary extreme value distribution model with time as an explanatory variable. In this study, we build a new method for constructing the confidence interval regarding the non-stationary extreme value distribution by applying a theory of probability limit method test. Furthermore, by introducing a confidence interval based on probability limit method test into the non-stationary hydrological frequency analysis, uncertainty in design rainfall because of lack of observation information was quantified, and it is shown that assessment pertaining to both the occurrence risk of extremely heavy rainfall and changes in the trend of extreme rainfall accompanied with climate change is possible.

Uncertainty Evaluation in Hydrological Frequency Analysis Based on Confidence Interval and Prediction Interval
Keita Shimizu, Tadashi Yamada, Tomohito J. Yamada
Water, 12, 9, 2554, 2554, MDPI AG, 12 Sep. 2020, [Peer-reviewed]
Scientific journal, The shortage of extreme rainfall data gives substantial uncertainty to design rainfalls and causes predictions for torrential rainfall to deviate strongly from adopted probability distributions used in river planning. These torrential rainfalls are treated as outliers which existing studies do not evaluate. However, probability limit method test which its acceptance region expresses with high accuracy the range where observed ith order statistics could realize. Confidence interval which quantifies uncertainty of adopted distributions can be constructed by assuming that these critical values in both sides of the adopted region follow the same function form applied to actual observed data. Furthermore, its validity is proved through comparison of confidence interval derived from ensemble downscaling calculations. In addition, these critical values are almost in accordance with outliers in samples from the ensemble downscaling calculations. Therefore, prediction interval which expresses the range that an unknown observed datum can take is constructed by extrapolating the critical values for limit estimation of a future datum. In this paper, quantification method of uncertainty of design rainfall and occurrence risk of outliers in the traditional framework, using the proposed confidence interval and prediction interval, is shown. Moreover, their application to future climate by using Bayesian statistics is explained.

Evaluation for Characteristics of Tropical Cyclone Induced Heavy Rainfall over the Sub-basins in The Central Hokkaido, Northern Japan by 5-km Large Ensemble Experiments
Tsuyoshi Hoshino, Tomohito J. Yamada, Hiroaki Kawase
Atmosphere, 11, 5, 435, 435, MDPI AG, 25 Apr. 2020, [Peer-reviewed]
English, Scientific journal, Previous studies have shown that the acceleration of global warming will increase the intensity of rainfall induced by tropical cyclones (TCs) (hereinafter referred to as “TC-induced rainfall”). TC-induced rainfall is affected by TC position and topography (slope shape and direction). Thus, TC-induced rainfall is expected to vary by sub-basin due to varying topographies. However, these relationships have not been explained, as historical TCs, which occurred several decades earlier, do not exhaustively encompass all TC positions that could potentially affect each basin. We used large ensemble regional climate model experiments with 5 km grid spacing, which enabled us to prepare a huge TC database for understanding the characteristics of TC-induced rainfall over sub-basins. We quantified the characteristics of TC-induced rainfall (rainfall volume, relationship between TC position and rainfall intensity, and contribution of TC intensity on rainfall) over four sub-basins in the Tokachi River basin, central Hokkaido, northern Japan. The results reveal differences in TC-induced rainfall characteristics between the sub-basins. In addition, the large ensemble data under a future climate scenario were used to evaluate future changes in the characteristics of TC-induced rainfall for each sub-basin.

Influence of the Long-Term Temperature Trend on the Number of New Records for Annual Maximum Daily Precipitation in Japan
Tomohito J. Yamada, Chhay Ngorn Seang, Tsuyoshi Hoshino
Atmosphere, 11, 4, 371, 371, MDPI AG, 10 Apr. 2020, [Peer-reviewed]
Scientific journal, Record-breaking precipitation events have been frequent in Japan in recent years. To investigate the statistical characteristics of the frequency of record-breaking events, observations can be compared with the values derived from sampling theory with a stationary state. This study counted the number of record-breaking daily and 3-day total precipitation events at 58 rain-gauge stations in Japan between 1901 and 2018. The average number of record-breaking events over the 118-year period was 5.9 for daily total precipitation, which is larger than the theoretical value of 5.4 derived using the assumption that the climate system over the same period was stationary. Sampling theory was used to incorporate the influence of the long-term temperature trend from the Clausius–Clapeyron relation associated with the saturation vapor pressure. In theory, the long-term temperature trend gives a similar number of observed record-breaking events when the long-term temperature trend is approximately 0.5 Kelvin/100 years.

Simulating flash floods using geostationary satellite-based rainfall estimation coupled with a land surface model
Dwi Prabowo Yuga Suseno, Tomohito J. Yamada
Hydrology, 7, 1, MDPI Multidisciplinary Digital Publishing Institute, 01 Mar. 2020
English, Scientific journal, Clarifying hydrologic behavior, especially behavior related to extreme events such as flash floods, is vital for flood mitigation and management. However, discharge and rainfall measurement data are scarce, which is a major obstacle to flood mitigation. This study: (i) simulated flash floods on a regional scale using three types of rainfall forcing implemented in a land surface model
and (ii) evaluated and compared simulated flash floods with the observed discharge. The three types of rainfall forcing were those observed by the Automated Meteorological Data Acquisition System (AMeDAS) (Simulation I), the observed rainfall from the Ministry of Land, Infrastructure and Transportation (MLIT) (Simulation II), and the estimated rainfall from the Multi-purpose Transport Satellite (MTSAT), which was downscaled by AMeDAS rainfall (Simulation III). MLIT rainfall observations have a denser station network over the Ishikari River basin (spacing of approximately 10 km) compared with AMeDAS (spacing of approximately 20 km), so they are expected to capture the rainfall spatial distribution more accurately. A land surface model, the Minimal Advance Treatments of Surface Interaction and Runoff (MATSIRO), was implemented for the flash flood simulation. The river flow simulations were run over the Ishikari river basin at a 1-km grid resolution and a 1-h temporal resolution during August 2010. The statistical performance of the river flow simulations during a flash flood event on 23 and 24 August 2010 demonstrated that Simulation I was reasonable compared with Simulation III. The findings also suggest that the advantages of the MTSAT-based estimated rainfall (i.e., good spatial distribution) can be coupled with the benefit of direct AMeDAS observations (i.e., representation of the true rainfall).

Future change of tropical cyclone induced rainfall over the Tokachi River Basin, Northern Japan using database for policy decision making for future climate change (d4PDF)　　　　　　　　　　　　　　　
Tsuyoshi Hoshino, Tomohito J. Yamada, Hiroaki Kawase
22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division, IAHR-APD 2020: "Creating Resilience to Water-Related Challenges", International Association for Hydro-Environment Engineering and Research (IAHR), 2020
English, International conference proceedings, Previous studies have shown that the acceleration of global warming will intensify the intensity of rainfall induced by tropical cyclones (TCs) (hereinafter referred to as “TC-induced rainfall”). TC-induced rainfall is affected by TC intensity, position and topography (slope shape and direction). It means that TC-induced rainfall is expected to vary by sub-basin due to varying topographies. However, relationships between TC intensity, position and topography have not been explained, as historical TCs, which occurred several decades earlier, do not exhaustively encompass all TC intensities and positions that could potentially affect each basin. In this study, we used large ensemble regional climate model experiments with 5 km grid spacing, which enabled us to prepare a huge TC database for understanding the characteristics of TC-induced rainfall over sub-basins. We quantified the characteristics of TC-induced rainfall (relationship between TC position and rainfall intensity, and contribution of TC intensity on rainfall) over two sub-basins in the Tokachi River basin, central Hokkaido, northern Japan. The results reveal differences in TC-induced rainfall characteristics between the two sub-basins. In addition, the large ensemble data under a future climate scenario were used to evaluate future changes in the characteristics of TC-induced rainfall for the sub-basins.

Comparison of hydrological models to determine flood characteristics for the Tokachi River, Hokkaido (Japan)　　　　　　　　　　　　　　　
Mark Hegnauer, Tsuyoshi Hoshino, Tomohito J. Yamada
22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division, IAHR-APD 2020: "Creating Resilience to Water-Related Challenges", International Association for Hydro-Environment Engineering and Research (IAHR), 2020
English, International conference proceedings, In 2016 Hokkaido (northernmost island in Japan) experienced extreme rainfall, resulting in severe flood damage due to the four typhoons. Climate change is expected to increase the intensity of typhoons that will cause heavy rainfall in Hokkaido in the future. Better understanding the dynamics of these events, a modelling study is conducted to simulate past and future flood dynamics. The study includes an ensemble meteorological events for past and future climate conditions. A set of over 8,000 events are used as input to multiple rainfall-runoff models. The ensemble of models includes both semi and fully distributed models and all cover the river basin of the Tokachi River. The models simulate the hydrological processes differently and differ in the level of detail they simulate these processes. The multimodel ensemble is used to investigate the importance of the different processes in the simulation of extreme flood events in Hokkaido. The results of the model comparison can be used to further develop the models to optimize their use in the flood risk assessment for Hokkaido and potentially Japan. The comparison is a joint effort of a consortium of researchers from Japan and The Netherlands.

Flood risk analysis for the Ishikari River considering rainfall patterns using downscaled D4PDF data　　　　　　　　　　　　　　　
Nguyen Thanh Thu, Makoto Nakatsugawa, Tomohito J. Yamada, Tsuyoshi Hoshino
22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division, IAHR-APD 2020: "Creating Resilience to Water-Related Challenges", International Association for Hydro-Environment Engineering and Research (IAHR), 2020
English, International conference proceedings, This study evaluated the flood risk of the Ishikari River basin under various climate change scenarios by using a large-ensemble dataset (d4PDF) with a high resolution of 5km. The top 20 and the top 36 rainfall events (corresponding to a return period of 150 years for the historical and future simulations, respectively) were selected. The Integrated Flood Analysis System (IFAS) was applied to simulate the flood risk under climate change scenarios after calibration and validation with observed discharge. After validation, we used the rainfall data from a large-ensemble dataset (d4PDF) as input to the IFAS model to assess the future flood risk. We found that the flood risk is expected to increase due to increases in rainfall for both historical and future simulations in the target basin. Moreover, the year of maximum rainfall (372 mm/72hr) does not agree with the year of greatest discharge of 17,982 m3/s under the historical simulation. In the future simulation, we obtained two cases with the same maximum rainfall amount (454 mm/72hr), but the peak discharges differed (30,018 m3/s versus 22,444 m3/s, respectively). This shows that the ranking of rainfall for a certain event does not necessarily coincide with the peak discharge ranking. As a result, river discharge volume depends not only on the total rainfall, but also on the temporal and spatial rainfall distribution. These results of this study will be helpful in developing flood disaster prevention plans in the target basin.

The analysis of future flood risk in Hokkaido, Northern Japan, using database for policy decision making for future climate change (d4PDF)　　　　　　　　　　　　　　　
Tomohito J. Yamada, Tsuyoshi Hoshino
22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division, IAHR-APD 2020: "Creating Resilience to Water-Related Challenges", International Association for Hydro-Environment Engineering and Research (IAHR), 2020
English, International conference proceedings, It is important to develop a plan to adapt to future heavy rainfall because heavy floods have frequently occurred in Japan over the past few years. This study examined the influence of climate change on rainfall characteristics over river basins in Hokkaido, Japan. We used dynamical downscaling to perform large ensemble regional climate experiments with a 5-km grid spacing from the d4PDF database for policy decision-making for future climate change. To evaluate the flood risk from various viewpoints, targets for dynamical downscaling were added: heavy rainfall events under the 2-K warmer condition and full 1-year dynamical downscaling for the past and 4-K warmer conditions. The results enabled us to quantify the influence of the degree of global warming on the annual maximum heavy rainfall and rainfall volume before heavy rainfall events. This research contributes to the expert committees for adaptation planning.

Fatality estimation by life loss evaluation model for the large-scale floods under future climate　　　　　　　　　　　　　　　
Sho Tomura, Manabu Chiba, Taro Yamamoto, Fumihiko Uemura, Shigekazu Masuya, Noriaki Omura, Takatoshi Yoshida, Atsushi Takeda, Tsuyoshi Hoshino, Tomohito Yamada, Makoto Nakatsugawa
22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division, IAHR-APD 2020: "Creating Resilience to Water-Related Challenges", International Association for Hydro-Environment Engineering and Research (IAHR), 2020
English, International conference proceedings, In recent years, large-scale floods frequently caused many fatalities in Japan. In Hokkaido, northern Japan, serious flood damage caused by hit of the three consecutive typhoons and approach of another typhoon in August 2016. After this, it became necessary to grasp accurate flood risk under future climate for considering climate change adaptation measures. The LIFESim model is used widely in Japan, which estimates numbers of fatalities based on water depth in flooded area. However, in the Netherlands, The life loss evaluation model has been used to grasp human damage in the national risk assessment project called Floris. This model considers not only flood depth but also water velocity and rise rate of water. In this study, we simulated floods for heavy rainfall events over the Tokachi River basin in Hokkaido under past and future climate detected from large ensemble climate projection data (d4PDF). We estimated the fatality in the urban area of Obihiro city located in the center of the Tokachi River basin from the simulation results by LIFESim model and life loss evaluation model. Finally, this study elucidated the differences of fatality by each model.

Projection for future change of confidence interval and prediction interval of extreme rainfalls based on Bayesian method using a large ensemble data set　　　　　　　　　　　　　　　
Keita Shimizu, Tadashi Yamada, Tomohito Yamada
22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division, IAHR-APD 2020: "Creating Resilience to Water-Related Challenges", International Association for Hydro-Environment Engineering and Research (IAHR), 2020
English, International conference proceedings, The main purpose of hydrological frequency analysis is to estimate hydrological quantity with design return period. In traditional hydrological frequency analysis, we estimate T-year hydrological quantity by using observed data which were accumulated for several decades. However, observed data of extremes which were accumulated so far are so limited ones that the design hydrological quantity includes uncertainty to a large extent. Moreover, one of the difficulties caused by the shortage of extreme value data is not to predict record heavy rainfall which deviate greatly from an adopted probability distribution used for river planning. So, it is often impossible to evaluate record heavy rainfalls and these rainfalls are treated as unexpected. Therefore, we propose a new hydrological frequency analysis introducing confidence interval and prediction interval based on probability limit method test. By introducing this confidence interval into hydrological frequency analysis, uncertainty of design hydrological quantity can be quantified. Also, by introducing this prediction interval, it can be possible to predict the scale and occurrence risk of catastrophic heavy rainfalls. In addition, another difficulty of hydrological frequency analysis is how to manage non-stationarity of rainfall which is caused by climate change. To manage non-stationarity of rainfall, using Bayesian statistics is effective. In this research, Bayesian update of confidence interval and prediction interval derived from past observed data was conducted by using a large ensemble database. In this research, a theoretical framework of hydrological frequency analysis introducing confidence interval and prediction interval and update method of these intervals using Bayesian statistics are shown.

RELATIONSHIP BETWEEN VERTICAL VORTEX STRUCTURE AND PRECIPITATION INTENSITY IN A LINE-SHAPED RAIN BAND IN HOKKAIDO IN SEPTEMBER 2014
Yuta OHYA, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 76, 2, I_193, I_198, Japan Society of Civil Engineers, 2020
Scientific journal

High wave coniditions due to typhoons measured at an offshore observation tower
Yasuyuki Baba, Teruhiro Kubo, Nobuhito Mori, Yasunori Watanabe, Tomohito Yamada, Ayumi Saruwatari, Junichi Otsuka, Yusuke Uchiyama, Junichi Ninomiya, Tomoya Shimura
22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division, IAHR-APD 2020: "Creating Resilience to Water-Related Challenges", 2020
International conference proceedings, This paper shows some observation results on high wave condition due to typhoons measured at an offshore observation tower. Japan is affected by typhoons every year, and some typhoons cause serious damages in Kii peninsula and its surrounding areas sometimes. In 2018, three typhoons (No.20, 21, 24) approached around the Kii peninsula, and the severe wave conditions caused by the typhoon Jebi (No.21) and the typhoon Trami (No.24) are observed at the observation tower of SOO. During the typhoon Jebi and the typhoon Trami approaching, the maximum significant wave heights reach 9.60m by the typhoon Jebi and 11.09m by the typhoon Trami, respectively. On the other hand, wave condition caused by the typhoon Cimaron (No.20) is relatively milder than the ones by the typhoon Jebi and the typhoon Trami, even though a central atmospheric pressure and the distance between the center of the typhoon and the observation tower are similar to those of the typhoon Jebi and the typhoon Trami. In case of 2018, it is pointed out that the magnitude of high wave condition is associated with the offshore wave direction around Kii peninsula because the observation site opens to the south-west (between about 190deg and 240deg). In this paper, the factors and backgrounds related to high wave conditions by typhoons are discussed based on the observation results including other typhoon cases.

2014年9月に発生した線状降水帯における鉛直渦構造と降水強度の関係　　　　　　　　　　　　　　　
大屋祐太, 山田朋人
土木学会論文集B1(水工学), 76, 193, 198, 2020, [Peer-reviewed]
Abkhazian

船舶レーダによる 2018 年夏季の観測と 散乱理論に基づく粒径分布のパラメタ推定手法　　　　　　　　　　　　　　　
岡地寛季, 山田朋人
土木学会論文集B1(水工学), 76, 181, 186, 2020, [Peer-reviewed]

FACTOR ANALYSIS FOR SPATIAL DEVIATION OF HEAVY RAINFALL IN TERMS OF DYNAMIC AND THERMODYNAMIC EFFECT　　　　　　　　　　　　　　　
星野剛, 山田朋人
土木学会論文集B1(水工学), 76, 19, 24, 2020, [Peer-reviewed]

気候変動予測情報を用いた極値水文量の統計的推定　　　　　　　　　　　　　　　
清水啓太, 山田正, 山田朋人
河川技術論文集, 26, 19, 24, 2020, [Peer-reviewed]

EVALUATION OF HEAVY RAINFALL RISK OF TYPHOON HAGIBIS ASSOCIATED WITH TYPHOON TRACK
Tsuyoshi HOSHINO, Hiroki OKACHI, Yui TAKEHARA, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 76, 1, 414, 423, Japan Society of Civil Engineers, 2020, [Peer-reviewed]
Scientific journal

Assessing climate change impacts on extreme rainfall and severe flooding during the summer monsoon season in the Ishikari River basin, Japan
Thu Thanh Nguyen, Makoto Nakatsugawa, Tomohito J. Yamada, Tsuyoshi Hoshino
Hydrological Research Letters, 14, 4, 155, 161, Japan Society of Hydrology and Water Resources, 2020, [Peer-reviewed]
Scientific journal

Climate Change Impacts on Heavy Snowfall in Sapporo Using 5-km Mesh Large Ensemble Simulations
Sho Kawazoe, Masaru Inatsu, Tomohito J. Yamada, Tsuyoshi Hoshino
SOLA, 16, 233, 239, Meteorological Society of Japan, 2020, [Peer-reviewed]
Scientific journal

Effect of Human-Induced Land Disturbance on Subseasonal Predictability of Near-Surface Variables Using an Atmospheric General Circulation Model
Tomohito J. Yamada, Yadu Pokhrel
Atmosphere, 10, 11, 725, 725, MDPI AG, 19 Nov. 2019, [Peer-reviewed]
Scientific journal, Irrigation can affect climate and weather patterns from regional to global scales through the alteration of surface water and energy balances. Here, we couple a land-surface model (LSM) that includes various human land-water management activities including irrigation with an atmospheric general circulation model (AGCM) to examine the impacts of irrigation-induced land disturbance on the subseasonal predictability of near-surface variables. Results indicate that the simulated global irrigation and groundwater withdrawals (circa 2000) are ~3600 and ~370 km3/year, respectively, which are in good agreement with previous estimates from country statistics and offline–LSMs. Subseasonal predictions for boreal summers during the 1986–1995 period suggest that the spread among ensemble simulations of air temperature can be substantially reduced by using realistic land initializations considering irrigation-induced changes in soil moisture. Additionally, it is found that the subseasonal forecast skill for near-surface temperature and sea level pressure significantly improves when human-induced land disturbance is accounted for in the AGCM. These results underscore the need to incorporate irrigation into weather forecast models, such as the global forecast system.

べイズ手法を用いた信頼区間の将来変化予測-アンサンブル気候予測データへの適用-　　　　　　　　　　　　　　　
清水 啓太, 山田 正, 山田 朋人
土木学会論文集B1(水工学) Vol.75, Nov. 2019, [Peer-reviewed]
Japanese, Scientific journal

ベイズ手法に基づくアンサンブル気候予測データを用いた信頼区間の更新　　　　　　　　　　　　　　　
清水 啓太, 山田 正, 山田 朋人
水文・水資源学会2019年度研究発表会要旨集, Sep. 2019
Japanese, Scientific journal

信頼区間・予測区間を導入した水文頻度解析における不確実性評価　　　　　　　　　　　　　　　
清水 啓太, 山田 正, 山田 朋人
河川技術論文集, Jun. 2019, [Peer-reviewed]
Japanese, Scientific journal

Using Weather Pattern Recognition to Classify and Predict Summertime Heavy Rainfall Occurrence over the Upper Nan River Basin, Northwestern Thailand
Dzung Nguyen-Le, Tomohito J. Yamada
Weather and Forecasting, 34, 2, 345, 360, American Meteorological Society, 01 Apr. 2019, [Peer-reviewed]
Scientific journal,
In this study, self-organizing maps in combination with K-means clustering are used to objectively classify the anomalous weather patterns (WPs) associated with the summertime [May–June (MJ) and July–August–September (JAS)] heavy rainfall days during 1979–2007 over the Upper Nan River basin, northwestern Thailand. The results show that in MJ, intensive rains are mainly brought by the remarkable enhancement of the westerly summer monsoon. Meanwhile, westward-propagating tropical disturbances including tropical cyclones are the primary factors that reproduce heavy rainfall over the Upper Nan in JAS. These results also suggest that the occurrence time of local heavy rainfall is strongly related to the seasonal transition of the summer monsoon over the Indochina Peninsula. The classification results are then implemented with the perfect prognosis and analog method to predict the occurrence (yes/no) of heavy rainfall days over the studied basin in summer 2008–17 using prognostic WPs from the operational Japan Meteorological Agency Global Spectral Model (GSM). In general, the forecast skill of this approach up to 3-day lead times is significantly improved, in which the method not only outperforms GSM with the same forecast ranges, but also its 3-day forecast is better than the 1–2-day forecasts from GSM. However, the false alarms ratio is still high, particularly in JAS. Nevertheless, it is expected that the new approach will provide warning and useful guidance for decision-making by forecasters or end-users engaging in water management and disaster prevention activities.

Analyses of Extreme Precipitation Associated with the Kinugawa River Flood in September 2015 Using a Large Ensemble Downscaling Experiment
Fujita Mikiko, Sato Tomonori, Yamada Tomohito J, Kawazoe Sho, Nakano Masuo, Ito Kosuke
JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN, 97, 2, 387, 401, Apr. 2019, [Peer-reviewed]

RAINFALL OBSERVATION IN THE COASTAL AREA WITH OPTICAL DISDROMETERS IN THE SUMMER OF 2013
岡地寛季, 山田朋人, 渡部靖憲, 猿渡亜由未, 大塚淳一, 森信人, 馬場康之, 久保輝広, 二宮順一, 内山雄介, 水谷英郎
土木学会論文集 G(環境)(Web), 75, 5, I_41, I_46, 公益社団法人 土木学会, 2019, [Peer-reviewed]
Japanese, Scientific journal

2016年北海道豪雨災害を対象としたアンサンブル気象予測を用いた河川水位，河床変動及び氾濫形態の予測可能性　　　　　　　　　　　　　　　
ムハマド イザーズ, ハズミー, ビン スハイミ, 山田朋人, 久加朋子, 清水康行, 奥田醇, 星野剛
土木学会論文集B1(水工学), 75, 1435, 1440, 2019, [Peer-reviewed]
Abkhazian

RESEARCH REPORT ON EXAMINATION AND IMPLEMENTATION STATUS OF CLIMATE CHANGE ADAPTATION IN THE FIELD OF FLOOD CONTROL IN THE NETHERLANDS (2ND REPORT)　　　　　　　　　　　　　　　
千葉学, 戸村翔, 山本太郎, 植村郁彦, 舛屋繁和, 吉田隆年, 大村宣明, 時岡真治, 佐々木博文, 濱田悠貴, 星野剛, 山田朋人, 中津川誠
河川技術論文集, 25, 49, 54, 2019, [Peer-reviewed]

ANALYSIS OF CAUSE OF HEAVY RAINFALL OVER TOKACHI RIVER BASIN UNDER HISTORICAL AND WARMER CLIMATE CONDITIONS USING A LARGE-ENSEMBLE DATASET(d4PDF)
Tsuyoshi HOSHINO, Tomohito J. YAMADA, Dzung Nguyen-Le
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 75, 5, I_25, I_31, Japan Society of Civil Engineers, 2019, [Peer-reviewed]
Scientific journal

FATALITY ESTIMATION BY “FLORIS MODEL” FOR THE LARGE-SCALE FLOODS UNDER FUTURE CLIMATE
Sho TOMURA, Shigekazu MASUYA, Fumihiko UEMURA, Takatoshi YOSHIDA, Noriaki OOMURA, Manabu CHIBA, Taro YAMAMOTO, Hirokazu OKABE, Hirofumi SASAKI, Ayaka KOBAYASHI, Tsuyoshi HOSHINO, Tomohito YAMADA, Makoto NAKATSUGAWA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 75, 2, I_1357, I_1362, Japan Society of Civil Engineers, 2019, [Peer-reviewed]
Scientific journal

Possible hydrological effect of rainfall duration bias in dynamical downscaling
Yuta Tamaki, Masaru Inatsu, Tomohito J. Yamada
Hydrological Research Letters, 13, 4, 55, 61, Japan Society of Hydrology and Water Resources, 2019, [Peer-reviewed]
Scientific journal

REVISING WAVE INDUCED TURBULENT MIXING AND ITS IMPACT ON TROPICAL CYCLONE
髙木 雅史, 森 信人, 二宮 順一, 志村 智也, 内山 雄介, 馬場 康之, 水谷 英朗, 久保 輝広, 渡部 靖憲, 大塚 淳一, 山田 朋人, 猿渡 亜由未
土木学会論文集. B2, 海岸工学 Journal of Japan Society of Civil Engineers. 土木学会海岸工学委員会 編, 75, 2, I_61, 66, 土木学会, 2019, [Peer-reviewed]
Japanese

ULTRASONIC BACKSCATTER MODEL ESTIMATING HEAT TRANSFER BY BUBBLE CLOUD IN THE OCEAN
猿渡 亜由未, 大塚 淳一, 馬場 康之, 久保 輝広, 水谷 英朗, 志村 智也, 二宮 順一, 山田 朋人, 内山 雄介, 森 信人, 渡部 靖憲
土木学会論文集. B2, 海岸工学 Journal of Japan Society of Civil Engineers. 土木学会海岸工学委員会 編, 75, 2, I_67, 72, 土木学会, 2019, [Peer-reviewed]
Japanese

HIGH WAVES DUE TO TYPHOONS IN THE SUMMER OF 2018 OBSERVED AT AN OBSERVATION TOWER
馬場 康之, 久保 輝広, 森 信人, 渡部 靖憲, 山田 朋人, 猿渡 亜由未, 大塚 淳一, 内山 雄介, 二宮 順一
土木学会論文集. B2, 海岸工学 Journal of Japan Society of Civil Engineers. 土木学会海岸工学委員会 編, 75, 2, I_271, 276, 土木学会, 2019, [Peer-reviewed]
Japanese

RAINFALL OBSERVATION IN THE COASTAL AREA WITH OPTICAL DISDROMETERS IN THE SUMMER OF 2013
岡地 寛季, 山田 朋人, 渡部 靖憲, 猿渡 亜由未, 大塚 淳一, 森 信人, 馬場 康之, 久保 輝広, 二宮 順一, 内山 雄介, 水谷 英郎
地球環境研究論文集 : 地球環境シンポジウム, 27, 41, 46, 土木学会, 2019, [Peer-reviewed]
Japanese

信頼区間の導入による確率洪水ピーク流量の不確実性評価― 総合確率法の拡張―　　　　　　　　　　　　　　　
清水啓太, 山田正, 山田朋人
土木学会論文集B1(水工学), Nov. 2018, [Peer-reviewed]
Japanese, Scientific journal

大量アンサンブル気候予測データを用いた大雨の時空間特性とその将来変化の分析
星野剛, 山田朋人, 稲津將, 佐藤友徳, 川瀬宏明, 杉本志織
土木学会論文集B1(水工学), 74, 5, I_13, I_18, Nov. 2018, [Peer-reviewed]

確率限界法検定に基づく信頼区間を用いた確率洪水ピーク流量の不確実性評価　　　　　　　　　　　　　　　
清水啓太, 山田正, 山田朋人
土木学会論文集G(環境), Sep. 2018, [Peer-reviewed]
Japanese, Scientific journal

タンクモデルを参考にした小学校高学年向けの地下水学習の教材開発
岩井尚人, 山中康裕, 根岸淳二郎, 山田朋人
水利科学, 364, 5, 59, 80, Aug. 2018, [Peer-reviewed]
Japanese, Scientific journal, 地下水の持続可能な利用は，その保全にとって必要である。地下水を保全す る態度を育むために，小学校教育の中で地下水について学ぶ機会を作ることは，重要なことである。本研究では，小学校高学年生が地下水涵養に関する森 林の機能などの地下水に関する基本的知識を学べる教材を，タンクモデルを参 考にして開発した。教材は，3 段タンクで構成され，森林領域の下にある帯水 層に設置したスポンジが水を貯留し，その水は装置外へゆっくりと流出するよ うになっている。教材で表現したのは，森林は主要な地下水の涵養域であるこ と，地下水は地表水に比べて滞留時間が長いことの 2 つである。教材を用いた 散水実験では，3 段のタンクそれぞれからの流出ピークのタイムラグや滞留時 間の違いなど，上記 2 点を定量的に確認した。小学校等の教員13名を対象に実 施した教材の実演と，彼らに対する聞き取り調査では，多くの教員は，小学校 児童にとって，上記 2 点が分かりやすいと判断した。

Heavy Rainfall Duration Bias in Dynamical Downscaling and Its Related Synoptic Patterns in Summertime Asian Monsoon
Yuta Tamaki, Masaru Inatsu, Dzung Nguyen-Le, Tomohito J. Yamada
Journal of Applied Meteorology and Climatology, 57, 7, 1477, 1496, American Meteorological Society, Jul. 2018, [Peer-reviewed]
Scientific journal, Dynamical downscaling (DDS) was conducted over Japan by using a regional atmospheric model with reanalysis data to investigate the rainfall duration bias over Kyushu, Japan, in July and August from 2006 to 2015. The model results showed that DDS had a positive rainfall duration bias over Kyushu and a dry bias over almost all of Kyushu, which were emphasized for extreme rainfall events. Investigated was the rainfall duration bias for heavy rainfall days, accompanied by synoptic-scale forcing, in which daily precipitation exceeded 30 mm day⁻¹ and covered over 20% of the Kyushu area. Heavy rainfall days were sampled from observed rainfall data that were based on rain gauge and radar observations. A set of daily climatic variables of horizontal wind and equivalent potential temperature at 850 hPa and sea level pressure, around southwestern Japan, corresponding to the sampled dates, was selected to conduct a self-organizing map (SOM) and K-means method. The SOM and K-means method objectively classified three synoptic patterns related to heavy rainfall over Kyushu: strong monsoon, weak monsoon, and typhoon patterns. Rainfall duration had a positive bias in western Kyushu for the strong monsoon pattern and a positive bias in southern and east-coast Kyushu for the typhoon pattern, whereas there was little rainfall duration bias in the weak monsoon pattern. The bias for the typhoon pattern was related to rainfall events with a strong rainfall peak. The results suggest that bias correction for rainfall duration would be required for accurately estimating direct runoff in a catchment area in addition to the precipitation amount.

北海道における気候変動に伴う洪水外力の変化　　　　　　　　　　　　　　　
山田朋人, 星野剛, 舛屋繁和, 植村郁彦, 吉田隆年, 大村宣明, 山本太郎, 千葉学, 戸村翔, 時岡真治, 佐々木博文, 濱田悠貴, 中津川誠
河川技術論文集, 24, 391, 396, Jun. 2018, [Peer-reviewed]
Japanese

Synoptic climatology of winter daily temperature extremes in Sapporo, northern Japan
M. A. Farukh, Tomohito J. Yamada
International Journal of Climatology, 38, 5, 2230, 2238, Wiley, Apr. 2018, [Peer-reviewed]
Scientific journal

Study on Improvement for Estimation of Lake Water Temperature
Watanuki Akira, Yamada Tadashi
Proceeding of Annual Conference, 31, 198, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2018
Japanese, Recently, various schemes related to solving water problems have been adopted. As these are common, there is planned management of basins. Therefore, it is necessary to accurately understand the state of the water area through monitoring and simulation. However, in the simulation of lake water temperature, it is very difficult to always keep the difference between observed value and calculated value within 1 ° C throughout the year, and as far as the authors know, such estimation method does not exist. Water temperature is an important water quality item in order to know the properties of lakes. Therefore, in this article, we aim to improve the estimation accuracy of lake water temperature with optimal interpolation method in heat budget method. And we studied on the annual number of days when the difference between the estimation result of water temperature and the mesuared value is within 1 ° C.

A STUDY ON IMPROVEMENTS FOR A SIMULATION OF DAILY MEAN WATER TEMPERATURE IN A SHALLOW LAKE
WATANUKI Akira, YAMADA Tadashi
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 74, 5, I_117, I_123, Japan Society of Civil Engineers, 2018
Japanese, In this article, we calculated the daily mean water temperature in a shallow lake by the optimal interpolation which is one of the data assimilation methods. We set three kinds of the weight of optimal interpolation to investigate an accuracy of calculation. As a result, the accuracy became quickly worse within 8 days of interplorating interval. In addition, when the interval of 8 days was longer, it was found that 30 to 50% of results by data assimilation was worse than results of heat budget method because results of both no data assimilation and by data assimilation were almost the same within 8 days.

CHARACTERISTICS OF CONVECTIVE CLOUD IN LINE-SHAPED RAIN BANDS FOR KANTO-TOHOKU HEAVY RAIN IN 2015
Yuta OHYA, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 5, I_229, I_234, Japan Society of Civil Engineers, 2018
Scientific journal

大規模洪水時における内外水同時氾濫解析モデルを用いた時空間的な浸水リスク評価　　　　　　　　　　　　　　　
米田駿星, 佐藤誠, 川村育男, 渡邊一晴, 松本勝治, 山田朋人
河川技術論文集, 25, 43, 47, 2018, [Peer-reviewed]

THE RISK ASSESSMENT OF THE FLOOD DAMAGE BY INNER AND RIVER WATER SIMULTANEOUS FLOOD ANALYSIS WITH UNCERTAINTY OF RAINFALL AND RUNOFF ANALYSIS
Hayase YONEDA, Makoto SATOH, Ikuo KAWAMURA, Masashi YAMAGUCHI, Katsuharu MATSUMOTO, Tomohito YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 5, I_1387, I_1392, Japan Society of Civil Engineers, 2018
Scientific journal

水資源の観点から見た，石狩川中流域に おける稲作の現状と将来への示唆　　　　　　　　　　　　　　　
金子直広, 山田朋人
水利科学, 62, 3, 52, 70, 2018, [Peer-reviewed]

INFLUENCE OF SEA SPRAY AND RAINDROP ON THE MOMENTUM EXCHANGE AT AIR-SEA INTERFACE
Hiroki OKACHI, Tomohito J. YAMADA, Yasunori WATANABE
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 4, I_265, I_270, Japan Society of Civil Engineers, 2018, [Peer-reviewed]
Scientific journal

ANALYSIS OF ANNUAL MAXIMUM PRECIPITATION OVER FIRST-CLASS RIVER DOMAINS IN JAPAN USING A LARGE-ENSEMBLE DATASET(d4PDF)
Tsuyoshi HOSHINO, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 4, I_187, I_192, Japan Society of Civil Engineers, 2018, [Peer-reviewed]
Scientific journal

CHARACTERISTICS OF THREE DIMENSIONAL WIND FIELDS FOR LINE-SHAPED RAIN BANDS
Yuta OHYA, Yoshikazu KITANO, Dzung NGUYEN-LE, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 4, I_43, I_48, Japan Society of Civil Engineers, 2018, [Peer-reviewed]
Scientific journal

ANALYSIS OF SPATIOTEMPORAL CHARACTERISTICS OF ANNUAL MAXIMUM RAINFALL USING A LARGE-ENSEMBLE DATASET(d4PDF) : APPLICATION TO TOKACHI RIVER BASIN
Tsuyoshi HOSHINO, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 74, 5, I_25, I_31, Japan Society of Civil Engineers, 2018, [Peer-reviewed]
Scientific journal

Orographic Dependency of Heavy Rainfall Events in Upper Reach of Tokachi River Basin
Yui TAKEHARA, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 74, 5, I_249, I_255, Japan Society of Civil Engineers, 2018, [Peer-reviewed]
Scientific journal

ESTIMATION OF ANNUAL MAXIMUM RAINFALLS BASED ON A MASSIVE ENSEMBLE CLIMATE PREDICTIONS IN ACTUAL RIVER BASIN
Fumihiko UEMURA, Shigekazu MASUYA, Takatoshi YOSHIDA, Noriaki OOMURA, Manabu CHIBA, Sho TOMURA, Taro YAMAMOTO, Shinji TOKIOKA, Hirofumi SASAKI, Yuki HAMADA, Tsuyoshi HOSHINO, Tomohito YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 5, I_115, I_120, Japan Society of Civil Engineers, 2018, [Peer-reviewed]
Scientific journal

LATENT AND SENSIBLE HEAT COEFFICIENTS BASED ON DRAG COEFFICIENT AFFECTED BY WAVE AGE AND SEA SPRAY
Hiroki OKACHI, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 5, I_1201, I_1206, Japan Society of Civil Engineers, 2018, [Peer-reviewed]
Scientific journal

CLIMATE STABILITY OF IN AN ENERGY BALANCE MODEL ASSOCIATED WITH OCEAN AND LAND PROCESSES
Nobutaka HOSOI, Tomohito YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 5, I_55, I_60, Japan Society of Civil Engineers, 2018, [Peer-reviewed]
Scientific journal

INFLUENCE OF UNCERTAINTY IN TRIBUTARY DISCHARGES ON PEAK WATER LEVEL AND PEAK DISCHARGE IN TOKACHI RIVER
Mai ANDO, Tsuyoshi HOSHINO, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 5, I_1249, I_1254, Japan Society of Civil Engineers, 2018, [Peer-reviewed]
Scientific journal

PROBABILITY RAINFALL CONSIDERING UNCERTAINTY BASED ON A MASSIVE ENSEMBLE CLIMATE PROJECTIONS IN ACTUAL RIVER BASIN
Shigekazu MASUYA, Fumihiko UEMURA, Takatoshi YOSHIDA, Noriaki OOMURA, Manabu CHIBA, Sho TOMURA, Taro YAMAMOTO, Shinji TOKIOKA, Hirofumi SASAKI, Yuki HAMADA, Tsuyoshi HOSHINO, Tomohito YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 5, I_121, I_126, Japan Society of Civil Engineers, 2018, [Peer-reviewed]
Scientific journal

Effects of Rain Droplets and Sea Sprays on the Momentum and Latent Heat Fluxes
H. Okachi, T. J. Yamada, Y. Watanabe, J. Ohtsuka
International Association for Hydro-Environment Engineering and Research (IAHR)-Asia Pacific Division (APD) Congress: Multi-Perspective Water for Sustainable Development, IAHR-APD 2018., 1, 493, 501, 2018, [Peer-reviewed]
English, International conference proceedings, © Proceeding of the 21st LAHR-APD Congress 2018. All rights reserved. Various fluxes are always exchanged at the air-sea surface. Considering flux exchanges in furious storm condition, there are much rain droplets and sea sprays generated from wave breaks. Sea sprays are instantly accelerated by local wind as they are generated. They have substantial mass. Therefore, momentum is conveyed by these droplets from the atmosphere to the ocean Focusing on the raindrops, they have horizontal speed more than wind speed when reaching the near-sea surface. That is, raindrops accelerate horizontal wind speed, however, there is no confirmation. Additionally, sea spray transfers latent heat extracted from the atmosphere in the process of its phase change. In this research, parameterization of momentum exchange at the air-sea surface is reconsidered concerning about drag coefficient. The drag coefficient increases as wind speed increases. We propose an equation which includes the effect of raindrops on the equation of drag coefficient that takes into account of sea spray and the characteristics of momentum exchange coefficient related to rainfall intensity and wind velocity. We also perform marine observation from 2013 to 2016 at an observational tower in Wakayama-prefecture, Japan, where typhoon often hits. Several typhoons passed near the tower for four years. We further conduct wind tunnel experiments to directly observe sea sprays (diameter > 72 μm) for six high wind speed conditions (U10=23∼28m/s).

NEW HYDROLOGICAL FREQUENCY ANALYSIS INTRODUCING CONFIDENCE INTERVAL OF PROBABILITY DISTRIBUTION MODELS BASED ON PROBABILITY LIMIT METHOD TEST
Keita SHIMIZU, Tomohito YAMADA, Tadashi YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 74, 4, I_331, I_336, Japan Society of Civil Engineers, 2018, [Peer-reviewed]
Japanese, Scientific journal

RESPONSE OF THE OCEAN SURFACE LAYER WITH BREAKING WAVES IN FETCH-LIMITED WIND CONDITIONS
SARUWATARI Ayumi, MORI Nobuhito, WATANABE Yasunori, SAKAGAWA Ryota, OTSUKA Junichi, BABA Yasuyuki, KUBO Teruhiro, MIZUTANI Hideaki, NINOMIYA Junichi, YAMADA Tomohito, UCHIYAMA Yusuke
Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 74, 2, I_67, I_72, 公益社団法人 土木学会, 2018, [Peer-reviewed]
Japanese

SEASONAL VARIABILITY OF WATER EXCHANGE AT THE ENTRNCE OF A SEMI-ENCLOSE BAY AND ITS UNDERLYING MECHANISMS
OKADA Nobue, OTSUKA Junichi, YAMADA Tomohito, SARUWATARI Ayumi, NINOMIYA Junichi, UCHIYAMA Yusuke, TADA Hiroaki, ENDO So, BABA Yasuyuki, MIZUTAMI Hideaki, KUBO Teruhiro, MORI Nobuhito, WATANABE Yasunori
Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 74, 2, I_667, I_672, 公益社団法人 土木学会, 2018, [Peer-reviewed]
Japanese

Classification and forecast of heavy rainfall in northern Kyushu during Baiu season using weather pattern recognition
Dzung Nguyen-Le, Tomohito J. Yamada, Duc Tran-Anh
ATMOSPHERIC SCIENCE LETTERS, 18, 8, 324, 329, WILEY, Aug. 2017, [Peer-reviewed]
English, Scientific journal, In this study, the Self-Organizing Maps in combination with K-means clustering technique are used for classification of synoptic weather patterns inducing heavy rainfall exceeding 100mmday(-1) during the Baiu season (June-July) of 1979-2010 over northern Kyushu, southwestern Japan. It suggests that these local extreme rainfall events are attributed to four clustered patterns, which are primarily related to the Baiu front and the extratropical/tropical cyclone/depression activities and represented by the intrusion of warm and moist air accompanied by the low-level jet or cyclonic circulation. The classification results are then implemented with the analogue method to predict the occurrence (yes/no) of local heavy rainfall days in June-July of 2011-2016 by using the prognostic synoptic fields from the operational Japan Meteorological Agency (JMA) Global Spectral Model (GSM). In general, the predictability of our approach evaluated by the Equitable Threat Score up to 7-day lead times is significantly improved than that from the conventional method using only the predicted rainfall intensity from GSM. Although the false alarm ratio is still high, it is expected that the new method will provide a useful guidance, particularly for ranges longer than 2 days, for decision-making and preparation by weather forecasters or end-users engaging in disaster-proofing and water management activities.

REGIONAL REGRESSION ANALYSIS OF DROUGHT RIVER DISCHARGES IN SNOWY COLD AREAS UNDER CLIMATE CHANGE
Yoshitaka Sakata
Journal of JSCE, 72, 5, 253, 264, Feb. 2017, [Peer-reviewed]

Asessment of Climate Change Effect on Pecipitation Amount within River Domains of Hokkaido
Hoshino Tsuyoshi, Yamada Tomohito
Proceeding of Annual Conference, 30, 12, 12, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2017
Japanese, 2016年8月，4つの台風が北海道に相次いで接近・上陸し，全道各地に記録的な大雨をもたらした．これにより，氾濫や橋脚の流出などの大雨による被害が広域的に発生し，北海道だけでなく全国的にも前例のないほどの極めて深刻な水害となった。この記録的豪雨の背景には気候変動の影響が考えられ，気候変動へ適応した新しい水防災対策の構築が喫緊の課題として顕在化した．本研究ではこの新しい水防災対策を構築する上で基礎となる気候変動による流域内の降水量の変化を明らかにすることを目的に，気候予測データベース(d4PDF)に基づいて流域内の降水量を評価した．
十勝川流域において流域平均3日降水量，流域平均10日降水量を調べたところ，どりらも温暖化により降水量が増大する傾向にあり，気候変動により大雨の高頻度化および激甚化が引き起こされることが示唆された．また，流域平均10日降水量も増大していたことから気候変動を踏まえた水防災対策の構築するに当たっては土壌水分量の考慮の重要性がより一層高まるものと考えられる．

Specific energy in the jet stream and formation condition of the atmospheric blocking
Kitano Yoshikazu, Yamada Tomohito J.
Proceeding of Annual Conference, 30, 8, 8, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2017
Japanese, 中緯度における気象擾乱がもたらす極端現象の要因の一つとして，大気ブロッキングが挙げられる．ブロッキングは，移動性高気圧よりもスケールの大きな高気圧が高緯度側に張り出し，大気中上層において通常とは逆転した南北ジオポテンシャル高度勾配，温位勾配が一地域に一定期間（多くの研究では5日程度）継続した場合同定される．また，ブロッキングの強度は，ブロッキング高気圧と周囲との気圧差やブロッキング高低気圧間に形成される東風の強さで定義される．本研究は，Rossby (1950)が提唱し，Armi (1989)，Riffler (2005)により室内実験・現実大気のデータで検証された偏西風が有する比エネルギーの理論を用い，ブロッキングの流れ場が有する比エネルギーの大小からブロッキングを物理的に定義することを目的とする。ジェット気流が有する比エネルギーの式を現実大気場に適用可能とし、ブロッキングが発生するために必要な同エネルギーの下限値を導き出した。

METEOROLOGICAL CHARACTERISTICS OF LINE-SHAPED RAIN BAND EVENT
BASED ON MULTI-DOPPLER RADARS OVER SAPPORO AREA IN 2014
Ohya Yuta, Nagao Kenta, Yamada Tomohito
Proceeding of Annual Conference, 30, 28, 28, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2017
Japanese, 複数のドップラーレーダと変分原理を用いることによって大気の三次元場の議論が可能になる．本研究では，気象庁によって設置・管理されている２基のCバンドレーダを用い，2014年9月に札幌圏で発生した線状降水帯を対象に降水を伴う気象場を分析した．三次元的な風速場の解明によって線状降水帯などの予測及び対策を可能にし，大規模災害を防ぐことに役立つと考えられる．
使用した手法は，航空機搭載型のレーダによる観測のため考案され，その後地上レーダに特化した手法である．同手法は３項からなる二次元変分法を用いて計算する。 3項はそれぞれ極座標系から直交座標への内挿を行う項，質量保存項，平滑化項である.
解析対象は，札幌近郊に住む90万人に避難勧告が出され北海道で初となる特別警報となった2014年9月11日の豪雨である．観測結果を同化し日本付近の大気場を補間した気象庁数値モデルと比較した場合，レーダ解析の結果からはより詳細な風速ベクトルを検知でき，線状降水帯の南東に位置の降水域で大気の水平鉛直循環を発見した．また強い反射強度を示す部分では上昇気流が発生し深い積乱雲の構成に寄与していることも示唆された．

Uncertainty of river discharge associated with rainfall distributions for the 2016 Hokkaido heavy rainfall event
Kobayashi Ayaka, Shibata Kounosuke, Nguyen-Le Dzung, Yamada Tomohito
Proceeding of Annual Conference, 30, 39, 39, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2017
Japanese, 2016年8月の約2週間に4度の台風による豪雨で，北海道内では年降水量に匹敵する降雨量を記録し，河川氾濫や土砂災害等の甚大な災害が発生した．台風10号の大雨により, 南富良野町では堤防決壊及び河川氾濫が発生した. 本研究では, 南富良野町を含む空知川上流部に位置する金山ダムを対象流域とし，台風10号時の降雨流出特性を述べる．

河川整備計画や防災対策は主に地上雨量観測値を用いて行われている．雨量計とは，地上に到達した雨滴を直径20cmの転倒マスで計測するものである．北海道の一級水系流域においては114km²に1つある計算となる．しかし，豪雨をもたらす積乱雲の空間スケールが数kmであり，山間部は地形による降雨強度の時空間的なばらつきが大きい特徴を有することを考慮すると，雨量計の存在する位置により総降雨量の観測値にばらつきが生じる. 一方, レーダー雨量計は面的かつ高解像度での観測が可能だが，間接的に降水強度を推定していることなどにより, 精度限界が存在する．これら２つの観測手法を組み合わせた解析雨量が存在する．解析雨量はレーダーで観測した面的なデータを，地上雨量との比較で補正したものである．本研究で用いる降雨データは，国交省C-band，気象庁C-band，地上雨量計(アメダス及び国土交通省保有のもの)及び解析雨量である．

本研究は，降雨観測位置による不確実性について検討し，それらが対象流域に与える不確実性を定量化，さらには気象モデルによる2日前からの気象予測結果と比較, 検討をした．

ANALYSIS OF ENERGY IN JET STREAM FOCUSING ON THE ANALOGY BETWEEN ATMOSPHERE AND OPEN CHANNEL FLOW
Yoshikazu KITANO, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 73, 4, I_439, I_444, Japan Society of Civil Engineers, 2017, [Peer-reviewed]
Japanese, Scientific journal

STATISTICAL ANALYSIS OF TYPHOON RELATED EVENTS IN HOKKAIDO AND SURROUNDINGS IN THE LAST 56 YEARS INCLUDING THE 2016 HEAVY RAINFALL
Yoshikazu KITANO, Taro YAMAMOTO, Ayaka KOBAYASHI, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 73, 4, I_1231, I_1236, Japan Society of Civil Engineers, 2017, [Peer-reviewed]
Japanese, Scientific journal

SIMULATION OF TROPICAL CYCLONE 201610 (LIONROCK) AND ITS REMOTE EFFECT ON HEAVY RAINFALL IN HOKKAIDO
Dzung NGUYEN-LE, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 73, 4, I_199, I_204, Japan Society of Civil Engineers, 2017, [Peer-reviewed]
English, Scientific journal

METEOROLOGICAL CHARACTERISTICS OF A HEAVY SNOWFALL EVENT BASED ON MULTI-DOPPLER RADARS OVER SAPPORO AREA
Yuta OHYA, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 73, 5, I_269, I_274, Japan Society of Civil Engineers, 2017, [Peer-reviewed]
Japanese, Scientific journal

Relationship between atmospheric blocking and cold day extremes in current and RCP8.5 future climate conditions over Japan and the surrounding area
Yoshikazu Kitano, Tomohito J. Yamada
Atmospheric Science Letters, 17, 11, 616, 622, Wiley, Nov. 2016, [Peer-reviewed]
English, Scientific journal, Atmospheric blocking is one of the most impactful weather patterns in midlatitude regions, causing floods, droughts and unusually high or low temperatures. This study investigates the relationship between extremely cold days over Japan and its surroundings and North Pacific blocking in the European Centre for Medium-rangeWeather Forecasts (ECMWF) re-analysis (ERA-40), phase 5 of the Coupled Model Intercomparison Project (CMIP5) for historical weather and the representative concentration pathway 8.5 (RCP8.5) experiments based on nine climate model datasets in the boreal winter season. Under the climate change conditions based on the RCP8.5 future scenario, extreme cold days (i.e. the first percentile of cold days) over Japan and its surroundings will become weaker but occur more widely when blocking is generated over the northwestern Sea of Okhotsk and its surroundings, because the blocking frequency over this area will decrease and the intensity will weaken.

Climatological Characteristics of Heavy Rainfall in Northern Pakistan and Atmospheric Blocking over Western Russia
Tomohito J. Yamada, Daiki Takeuchi, M. A. Farukh, Yoshikazu Kitano
JOURNAL OF CLIMATE, 29, 21, 7743, 7754, AMER METEOROLOGICAL SOC, Nov. 2016, [Peer-reviewed]
English, Scientific journal, Pakistan and northwestern India have frequently experienced severe heavy rainfall events during the boreal summer over the last 50 years including an event in late July and early August 2010 due to a sequence of monsoon surges. This study identified five dominant atmospheric patterns by applying principal component analysis and k-means clustering to a long-term sea level pressure dataset from 1979 to 2014. Two of these five dominant atmospheric patterns corresponded with a high frequency of the persistent atmospheric blocking index and positive sea level pressure over western Russia as well as an adjacent meridional trough ahead of northern Pakistan. In these two groups, a negative sea surface temperature anomaly was apparent over the equatorial mid-to eastern Pacific Ocean. The heavy precipitation periods with high persistent blocking frequency in western Russia as in the 2010 heat wave tended to have 1.2 times larger precipitation intensity compared to the whole of the heavy precipitation periods during the 36 years.

Cyclic steps on ice
M. Yokokawa, N. Izumi, K. Naito, G. Parker, T. Yamada, R. Greve
Journal of Geophysical Research: Earth Surface, 121, 5, 1023, 1048, American Geophysical Union (AGU), May 2016, [Peer-reviewed]
English, Scientific journal, Boundary waves often form at the interface between ice and fluid flowing adjacent to it, suchas ripples under river ice covers, and steps on the bed of supraglacial meltwater channels. They may alsobe formed by wind, such as the megadunes on the Antarctic ice sheet. Spiral troughs on the polar ice capsof Mars have been interpreted to be cyclic steps formed by katabatic wind blowing over ice. Cyclic stepsare relatives of upstream-migrating antidunes. Cyclic step formation on ice is not only a mechanical butalso a thermodynamic process. There have been very few studies on the formation of either cyclic steps orupstream-migrating antidunes on ice. In this study, we performed flume experiments to reproduce cyclicsteps on ice by flowing water, and found that trains of steps form when the Froude number is larger thanunity. The features of those steps allow them to be identified as ice-bed analogs of cyclic steps in alluvial andbedrock rivers. We performed a linear stability analysis and obtained a physical explanation of the formationof upstream-migrating antidunes, i.e., precursors of cyclic steps. We compared the results of experimentswith the predictions of the analysis and found the observed steps fall in the range where the analysispredicts interfacial instability. We also found that short antidune-like undulations formed as a precursor tothe appearance of well-defined steps. This fact suggests that such antidune-like undulations correspondto the instability predicted by the analysis and are precursors of cyclic steps.

確率課程論に基づいた降雨流出解析における不確実性評価の理論的枠組みの提示
吉見和紘, Chao-Wen WANG, 山田正, 山田朋人
土木学会論文集B1（水工学）, 72, 4, Mar. 2016, [Peer-reviewed]
Japanese, Scientific journal

Estimation of daily mean water temperature using sensible and latent heat fluxes which are calculated at one altitude with meteorological data in lake -Example in Lake Inba
WATANUKI Akira, YAMADA Tadashi
Proceeding of Annual Conference, 29, 87, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2016
Japanese, The heat budget method is often used as a method to estimate water temperature. But meteorological data at two altitudes are needed to calculated sensible and latent heat fluxes using the gradient method and the Bowen ratio energy balance method. And the bulk method is able to calculate those at one altitude with meteorological data but bulk transfer coefficient must be generally given and atmosphere stability is calculated as neutrality. In this article, we calculated sensible and latent heat fluxes using the iterative approximation method, the bulk method and Kondo's theory at one altitude with meteorological data and estimated daily mean water temperature. As a result, the prediction didn't improve.

A STUDY ON LANDSLIDE ANALYSIS INDUCED BY RAINFALL BASED ON THE STOCHASTIC PROCESS
WANG Chao-Wen, YOSHIMI Kazuhiro, YAMADA Tadashi, YAMADA Tomohito
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 72, 4, I_1279, I_1284, Japan Society of Civil Engineers, 2016
Japanese, Most of the past studies on the analysis of landslides are evaluated by determinism. It means the analysis are only two results, stable and unstable. However in the real environment, there are a lot of uncertainty factors that would affect the occurrence of landslides. In the study, the authors consider the hydrological uncertainty and the variability of soil parameters of the slope to propose a new method for the risk evaluation of landslide induced by rainfall. The uncertainty has two types, one is the limitation of observation or experiment and the other one is and the error of data. For the landslides analysis, the uncertainty analysis can be separated by the external force from rainfall and the resistance force of slope stability. In considering the external force, it would focus on the analysis the relationship between rainfall and storage by using storage function model based on the uncertainty rainfall and the analysis of slope stability would consider the deviation of the soil parameters. Finally the occurrence of landslides can be summarized as like the risk evaluation during rainfall based on the stochastic process theory.

Fundamental Study of Real-time Short-term Rainfall Prediction System in Watershed: Case Study of Kinu Watershed in Japan
Tao Lu, Tomohito Yamada, Tadashi Yamada
12TH INTERNATIONAL CONFERENCE ON HYDROINFORMATICS (HIC 2016) - SMART WATER FOR THE FUTURE, 154, 88, 93, ELSEVIER SCIENCE BV, 2016, [Peer-reviewed]
English, International conference proceedings, This study focuses on the improvement of the accuracy and construction of a real-time, short-term rainfall prediction system in watershed, comparing the prediction results with radar observed rainfall intensity, to provide a reliable tool for disaster and water resource management. The short-term prediction of rainfall is very important for hydrologie forecasting for watershed with a short response time, especially under the global warming and extreme weather. Last September 9th (2015), heavy rain came a day after Tropical Storm Etau and triggered widespread flooding in Kinu Watershed. We use the Weather Research and Forecasting Model (WRF) to confirm the uncertainty of the rain prediction in Kinu watershed first, then will modify the WRF to suit the 6h, 12h, 24h rainfall prediction in Kinu watershed. Also, radar rainfall data will be employed to correct the WRF prediction in real-time meaning. Finally, we will check the possibility of general application of the system in other watersheds. We now are working on reproducing the heavy rain in Kinu watershed last September. We tried different microphysics, which describes the formation of cloud, to find one to reproduce the heavy rain in this case. The coverage, location of rain bands and distribution of heavy rainfall are applied to comparisons between calculations and observations by C-band radar. We found no Microphysics does well in this case and the area of heavy rain is underestimated by WRF, but the accumulated precipitation is overestimated. Detail insight at microphysics and modification are required. (C) 2016 The Authors. Published by Elsevier Ltd.

A nonlinear filter based on Fokker-Planck equation and its application on rainfall-runoff analysis
Daiwei Cheng, Yoshimasa Morooka, Tadashi Yamada, Tomohito J. Yamada
2016 3RD INTERNATIONAL CONFERENCE ON SYSTEMS AND INFORMATICS (ICSAI), 603, 608, IEEE, 2016
English, International conference proceedings, Rainfall-runoff process is the central issue of hydrology. The prediction of the runoff has many practical significances. In 1974, M. Hino had firstly applied the Kalman filter in forecasting the rainfall- runoff process, since then many new filters had been suggested and applied in rainfall- runoff process. However, there is no filter can help to recognize the physical meaning of the random external force.
On the other hand, recently, K. Yoshimi and T. Yamada have tried to use Fokker-Planck equation to study the uncertainty of stream flow due to the random fluctuation in precipitation. And this can be used in the filter theory to deal with nonlinear systems and also to find the physical meaning of the system noise.
The present study is based on K. Yoshimi and T. Yamada's work, aimed at directly using Fokker-Planck equation in the prediction step of filtering, and applied it in the rainfall-runoff process

The evaluation of uncertainty in rainfall-runoff process using stochastic process theory
Cheng Daiwei, Yamada Tadashi, Yamada Tomohito
Proceeding of Annual Conference, 29, 128, 128, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2016
Japanese, When dealing with the hydrological system, it is very hard to use the first principle directly because of the large scale of the system. So modeling and simplify has to be done. However, there are information neglected by these models and it causes the uncertainty when people want to predict the system. A lot of research had been done in order to solve the above problem. For example, Yoshimi and Yamada had tried to consider the uncertainty of rainfall as a kind random external force of the rainfall-runoff system and to explain the system by stochastic differential equation. However, the infiltration process has not been considered in their study This study is based on Yoshimi and Yamada’s work and aimed at find out the how the uncertainty of rainfall affects the runoff when you consider the infiltration process.

THE RELATIONSHIP BETWEEN EXPLOSIVE CYCLON THROUGH NORTHERN JAPAN AND PACIFIC BLOCKING
Yoshikazu KITANO, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 72, 4, I_121, I_126, Japan Society of Civil Engineers, 2016, [Peer-reviewed]
Scientific journal

RELATIONSHIP BETWEEN EXPLOSIVELY DEVELOPING EXTRATROPICAL CYCLONE INTENSITY AND LOCATION OF ATMOSPHERIC BLOCKING IN CURRENT AND FUTURE CLIMATE CONDITIONS
Yoshikazu KITANO, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 72, 5, I_233, I_239, Japan Society of Civil Engineers, 2016, [Peer-reviewed]
Scientific journal

The Comparison between Explosive Cyclone and Typhoon over Northern Japan in the Current and Future Climate
Yoshikazu Kitano, Tomohito J. Yamada
Procedia Engineering, 154, 726, 732, Elsevier BV, 2016, [Peer-reviewed]
Scientific journal

IN SITU MEASUREMENTS OF ATMOSPHERIC AEROSOL OVER THE OCEAN
SARUWATARI Ayumi, WATANABE Yasunori, YAMADA Tomohito, OTSUKA Junichi, BABA Yasuyuki, MIZUTANI Hideaki, KUBO Teruhiro, UCHIYAMA Yusuke, MORI Nobuhito, NINOMIYA Junichi
Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)), 72, 2, I_537, I_547, 公益社団法人 土木学会, 2016, [Peer-reviewed]
Japanese, Sea spray is one of the important factors to affect weather conditions over the ocean in terms of constituting an aerosol as well as determining air-sea transport of heat, moisture and momentum. The final goal of this study is to explain the relationship between sea-spray generation and conditions of the atmosphere and ocean for a more accurate prediction of the amount of sea spray. This study conducted three-year field observations of atmospheric aerosol at an offshore observatory in Tanabe Bay, Wakayama. Large-scale (> 100 km) distribution of atmospheric aerosol was found to dominate the concentration of the observed aerosol less than 1 μm in normal weather conditions. During storm events with strong winds from the Pacific Ocean, however, the observed concentration monotonically increased with the wind speed, which is considered to be a result of the increase in oceanic aerosol derived from sea spray.

A STUDY ON DESTRUCTION OF THERMOCLINE AND VERTICAL MIXING BASED ON FIELD MEASUREMENT
KUBO Shinya, NINOMIYA Junichi, MORI Nobuhito, BABA Yasuyuki, MIZUTANI Hideaki, KUBO Teruhiro, UCHIYAMA Yusuke, WATANABE Yasunori, YAMADA Tomohito, OTSUKA Junichi, SARUWATARI Ayumi
Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 72, 2, I_487, I_492, 公益社団法人 土木学会, 2016, [Peer-reviewed]
Japanese,  This study focuses on the process of thermocline's destruction and reformation during typhoons using field observation data. The thermocline has a large effect on the circulation and would be a factor to make water worse. Therefore, it is necessary to understand its process deeply. In this study, the stability of density stratification was evaluated based on the Brant-Vaisala frequency and the Richardson number. The results suggested that high wave destroyed the stratification and high wind mixed ocean water vertically more energetically during stratified season. On the other hand, is was found that stratification was unstable regardless of typhoon intensity during unstratified season. Moreover, the characteristics of water-mass were evaluated on the TS diagram during unstratified season.

UPPER-OCEAN DYNAMICS AND WATER-EXCHANGE AT THE ENTRANCE OF A SEMI-ENCLOSE BAY UNDER STRATIFIED AND UNSTRATIFIED CONDITIONS
UCHIYAMA Yusuke, YOSHIKI Tomomichi, TADA Hiroaki, BABA Yasuyuki, MIZUTANI Hideaki, KUBO Teruhiro, MORI Nobuhito, SARUWATARI Ayumi, OTSUKA Junichi, NINOMIYA Junichi, WATANABE Yasunori, YAMADA Tomohito
Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering), 72, 2, I_493, I_498, 公益社団法人 土木学会, 2016, [Peer-reviewed]
Japanese,  For rigorious description of upper ocean dynamics and resultant volume transport at the mouth of Tanabe Bay, Wakayama, Japan, a comprehensive field campaign was conducted from summer to fall of 2015. The vertical structure of transient dynamics in the surface boundary layer and consequent water exchange at the mouth are characterized by high-frequency variability peaked at around the semi-diurnal period as well as in the lower-frequency subtidal band centered at 3 day period, consistent with the previous modeling study. A spectral coherence analysis indicates that near-surface currents are mainly driven by wind stress peaked at the diurnal frequency, whereas subsurface currents fluctuate rather by semi-diurnal internal tides. The upper ocean cools down gradually, corresponding to seasonal transition from summer to fall condition. However, an abrupt cooling event is observed albeit in a calm local forcing condition where an offshore subtidal cold water intrusion induced remotely by the fluctuating Kuroshio path plays an essential role.

降雨の不確実性に基づく確率過程論を導入した堤防の信頼性評価
Chao-Wen WANG, 吉見和紘, 山田正, 山田朋人
土木学会論文集G（環境）, 71, 5, I_1, I_6, Japan Society of Civil Engineers, Sep. 2015, [Peer-reviewed]
Japanese, Scientific journal, Most of the past studies on the levee destruction are determinism that for the different flood conditions the levee is failure or not failure. However in the real environment, there are a lot of uncertainty factors that would affect the analysis result of the levee stability very seriously. In this study, the authors would consider the variability of soil parameters of levee and propose the new idea for the reliability evaluation of levee during floods by using the probability theory.
 In consideration of the different water level conditions, the probability of safety factor of levee can be estimated. When the levee is completely saturated, the safety factor is 80% smaller than 1.2 with considering the uncertainty of the soil parameters in the levee with 7.5 m height. And another water levels, like 7.50 m, 7.25 m and 7.0m is be estimated, here the high water level is 7.0 m assumed.
 In conclusions, with considering the variability of the soil parameters, the safety factor of levee is a distribution. Furthermore the driving force and resistance force of levee can be summarized as the reliable design analysis. Finally in this study, the risk of flood (including of levee destruction and overflow) can be evaluated with the change of water level.

確率過程論の導入による水文学的集中化法を用いた人体における放射能強度の確率分布に関する研究
崔 瑂芝, 佐々木 翔太, 吉見 和紘, 山田 正, 山田 朋人
第23回地球環境シンポジウム講演集, 23, 189, 192, 土木学会, Sep. 2015
Japanese

確率微分方程式の導入による降雨流出過程における降雨の不確実性の評価
吉見和紘, 山田正, 山田朋人
土木学会論文集B1(水工学), 71, 1, I_259, I_264, Japan Society of Civil Engineers, Mar. 2015, [Peer-reviewed]
Japanese, Scientific journal, This paper explained the uncertainty of discharge due to the uncertainty of rainfall theoretically and mathematically. The lumped rainfall-runoff model is represented by SDE (stochastic differential equation), because the temporal variation of rainfall is expressed by its average plus deviation, which is approximated by Gaussian distribution. As a result, this paper has shown that it is possible to evaluate the uncertainty of discharge by using the relationship between SDE and Fokker-Planck equation. Moreover, the results of this study show that the uncertainty of discharge increases as rainfall intensity rises and non-linearity about resistance grows strong. These results are clarified by PDFs (probability density function) that satisfy Fokker-Planck equation about discharge. It means the reasonable discharge can be estimated based on the theory of stochastic processes, and it can be applied to the probabilistic risk of flood management.

A NEW DIFFERENTIAL EQUATION OF MIXING LENGTH CONSIDERING ATMOSPHERIC STABILITY AND ITS APPLICABILITY TO ATMOSPHERIC BOUNDARY LAYER
QIAN Chaochao, YAMADA Tadashi
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 71, 5, I_283, I_288, Japan Society of Civil Engineers, 2015
Japanese, Numerical calculations of climate change and weather forecast has been widely carried out, and Monin-Obukhov length based vertical distribution of wind velocity (Log+Linear law) is used in the calculations typically. However, it is not suitable for the numerical calculations because the stability scale of Monin-Obukhov is an algebraic expression. Also, it is very difficult to give a physical interpretation that the scale of the mixing length is negative when the atmosphere is instable. In addition, the scale on the vertical direction of the mixed layer should be set a priori when the atmosphere is instable. In order to solve these problems, a new differential equation of physically rigorous mixing length with considering atmospheric stability has been proposed in this study. The precision of wind velocity distribution in the vertical direction was confirmed by both observed data and Monin-Obukhov length bese Log+Linear law in the study. The proposed stability length can be used more conveniently than existing Monin-Obukhov length based mixing length to deal with the boundary layer in atmospheric calculations such as GCM or weather models.

ROTATING FLUID EXPERIMENT WITH BOTTOM SUBJECTED TO HEATED AND COOLED
Ichinose Rinko, Kitano Yoshikazu, Yamada Tomohito, Watanabe Yasunori, Izumi norihiro
Proceeding of Annual Conference, 28, 100131, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2015
Japanese, The weather condition in the middle latitudes is controlled by westerly wind and high and low pressures, and these phenomena are interpreted as the baroclinic instability waves. A rotating fluid experiment by Fultz and Hide are known as the typical laboratory experiments of baroclinic instability waves. In this study, we introduced a new equipment having the unique feature characterized by the heated and cooled bottom. By this condition, 4-6 zonal wave numbers were observed and flow field were dynamically changed with time. At the sametime, it was observed that the vorticity on center changed with baroclinic waves with time.

A BASIC STUDY ON INTRODUCTION OF THEORY OF STOCHASTIC PROCESS INTO RAINFALL-RUNOFF ANALYSIS
YOSHIMI Kazuhiro, WANG Chao-Wen, YAMADA Tadashi, YAMADA Tomohito
Proceeding of Annual Conference, 28, 100107, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2015
Japanese, In this paper, we showed a theoretical framework to evaluate uncertainties of runoff process based on the theory of stochastic process. If a runoff model can be expressed an ordinary differential equation such as the storage-function, we can rewrite it as a stochastic differential equation (SDE) to include disordered component of rainfall. Moreover we can obtain the time evolution of probability density function about discharge from the correspondence relationship between SDE and the Fokker-Planck equation. Through means of this, we could show the uncertainty of discharge caused by rainfall uncertainty theoretically. This result shows the chance of introduction of this concept into river planning.

A case study of long-and short-term hydraulic state changes in embankment in Hokkaido
Satoshi Nishimura, Tetsuya Tokoro, Tomohito Yamada, Norihiro Izumi, Maria Fernanda Rivas
6th Japan-China Geotechnical Symposium, SJGS 2015, 34, 39, 2015
International conference proceedings, Mechanical stability of embankments such as road embankments and river dykes is significantly influenced by their internal hydraulic states, as represented by phreatic surface location and pore water pressure distribution. The mass transfer across the embankment surfaces through water infiltration and evapotranspiration, and the internal migration of pore water to/from foundation soil layers are considered to play a major role in dictating the evolution of the hydraulic state. This paper reports a case study in which hydraulic state variations in an embankment in Hokkaido were monitored over 9 months, including a winter period with ground surface freezing and a significant snow cover. The studied embankment was relatively new, constructed with artificially mixed clay and sand which were generated by nearby excavation. The monitoring records indicate a consistent trend of under-drainage to the foundation layer all during the 9 months, with the pore water pressure at deeper parts registering minimum values during winter and reaching maxima during summer. Explanations for this and other observed features were sought by performing unsteady unsaturated seepage flow analysis with some assumed surface input models. Although the adopted models are fairly crude, the analysis results offer important insights into factors that govern the hydraulic state of low-permeability embankment in snowy cold regions.

ESTIMATING GROUNDWATER LEVEL CHANGES BASED ON LAND SUBSIDENCE IN THE ISHIKARI RIVER BASIN
Tomohito J. YAMADA, Koki WACHI, Eiichi SUZUKI
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 71, 5, I_55, I_60, Japan Society of Civil Engineers, 2015, [Peer-reviewed]
Japanese, Scientific journal

THE STUDY OF THE ATMOSPHERIC CIRCULATION AND THE RIVER BASIN WATER BUDGET BY USING AN AGCM WITH THE REPRESENTATIION OF HUMAN IMPACTS
Daiki TAKEUCHI, Tomohito J. YAMADA, Yadu N. POKHREL
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 71, 5, I_189, I_196, Japan Society of Civil Engineers, 2015, [Peer-reviewed]
Japanese, Scientific journal

RAINFALL RE-ESTIMATION ASSOCIATED WITH DIFFERENCES IN THE DETECTION TIME OF RAINFALL BETWEEN X-BAND MP RADAR AND RAINGAUGE
Akihiro SUZUKI, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 71, 5, I_257, I_262, Japan Society of Civil Engineers, 2015, [Peer-reviewed]
Japanese, Scientific journal

ROTATING FLUID EXPERIMENT WITH BOTTOM SUBJECTED TO HEATED AND COOLED
Rinko ICHINOSE, Yoshikazu KITANO, Tomohito. J. YAMADA, Yasunori WATANABE, Norihiro IZUMI
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 71, 5, I_289, I_294, Japan Society of Civil Engineers, 2015, [Peer-reviewed]
Japanese, Scientific journal

UNCERTAINTY OF PEAK RUNOFF HEIGHT ASSOCIATED WITH UNCERTAINTY OF WATER HOLDING CAPACITY AND RAINFALL PATTERN
Intan SUPRABA, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 71, 5, I_17, I_22, Japan Society of Civil Engineers, 2015, [Peer-reviewed]
English, Scientific journal

AN APPLICATION OF HYDROLOGIC METHODOLOGY TO THE INTERNAL DOSE CALCULATION: THE INTAKE OF RADIOACTIVITY ON AGRICULTURAL PRODUCTS DERIVED FROM FALLOUT
Syota SASAKI, Hayase YONEDA, Tadashi YAMADA, Tomohito J. YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 71, 4, I_49, I_54, Japan Society of Civil Engineers, 2015, [Peer-reviewed]
English, Scientific journal

Multi-GCM by multi-RAM experiments for dynamical downscaling on summertime climate change in Hokkaido
Inatsu Masaru, Sato Tomonori, Yamada Tomohito J, Kuno Ryusuke, Sugimoto Shiori, Farukh Murad A, Pokhrel Yadu N, Kure Shuichi
Atmospheric Science Letters, 16, 3, 297, 304, 2015, [Peer-reviewed]
Scientific journal, © 2015 Royal Meteorological Society. The experiments with three general circulation models (GCMs) by three regional atmospheric models (RAMs) for the dynamical downscaling (DDS) have been performed to evaluate the uncertainty in the global warming response during summertime in Hokkaido, Japan. The results of a 10-year RAM integration nested into GCM under present or future climate conditions were synthesized after applying bias correction. For the target decades during which the global-mean temperature increases by 2K in each GCM, the DDS results indicate that surface air temperature and precipitation mostly depend on the GCM imposed as the lateral boundary condition.

POTENTIAL WATER STORAGE CAPACITY OF MOUNTAINOUS CATCHMENTS BASED ON CATCHMENT CHARACTERISTICS
SUPRABA Intan, YAMADA Tomohito J
水工学論文集 土木学会水工学委員会 編, 59, 4, I_151, 156, 土木学会, 2015
English, The majority of water catchments in Japan are located in mountainous areas that can produce large quantities of runoff, which may lead to flooding, erosion, and landslides. Thus, it is important to know the minimum total rainfall required to generate surface runoff by estimating the water storage capacity of each catchment. The threshold of minimum total rainfall required to generate surface runoff occurs when at least 95% of total rainfall becomes total loss rainfall such as infiltrates into the ground. The variation in this value is dependent on the catchment characteristics. Based on the relationship between total rainfall and total loss rainfall, the average values of minimum total rainfall required to generate surface runoff and total loss of saturated rainfall were 51.3 mm and 108.5 mm, respectively. Catchments consisting of a smaller area of sedimentary rock and higher values of drainage density, elongation ratio, and catchment width tended to have smaller values of minimum total rainfall required to generate surface runoff.

Synoptic climatology associated with extreme snowfall events in Sapporo city of northern Japan
M. A. Farukh, Tomohito J. Yamada
ATMOSPHERIC SCIENCE LETTERS, 15, 4, 259, 265, WILEY-BLACKWELL, Oct. 2014, [Peer-reviewed]
English, Scientific journal, Synoptic-scale atmospheric circulations are crucial for extreme snowfall events. On the basis of topmost 100 snowfall intensity days in Sapporo, Hokkaido, Japan over winter seasons from 1992 to 2011, this study uses principal component analysis and K-means clustering to characterize synoptic circulation patterns. Composite maps were constructed for sea-level pressure, 850 hPa moisture and wind field, and 500 hPa geopotential height. The circulation patterns of the topmost seven snowfall events were triggered by the advection of very cold airmass from eastern Siberia, anomalously huge moisture with northerly strong wind, active and stationary Aleutian low, and 500 hPa deep cold-core low over the southern Hokkaido.

Proposal of a Hydrological Model to Estimate a Number of Radioactive Atoms in the Human Body, Radioactivity and Internal Total Exposure Caused by Ingestion of Radioactive Isotopes
SASAKI SHOTA, YAMADA TADASHI, YAMADA TOMOHITO
水文・水資源学会誌, 27, 4, 170, 181, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 05 Jul. 2014
Japanese, This study provides a readily comprehensible hydrology-based model for estimation of the number of radioactive isotopes in the human body, intensity of radioactivity, and internal total exposure without the need for consideration of any complicated mechanism. For example, the International Commission on Radiological Protection has developed an exact model, which is regarded by radiologists as the standard method. However, that method is too complex for non-professional researchers of radiology, including hydrologists, to understand. In contrast, here we calculate the exposure attributable to the ingestion of radioactive isotopes by regarding the human body as a single tissue. Although this study does not involve consideration of a complicated mechanism, it does provide results with accuracy equal to the measured values of intensity of radioactivity obtained using a whole body counter.

A Fundamental Study on Water Profiles in Non-uiform Open Channel Flows with Stream-wise and Cross Sectional Variation of Channel Properties
QIAN Chaochao, YAMADA Tadashi
Water Science, 58, 1, 64, 99, Japan Forest Conservation Association, 2014
Japanese

DIURNAL CHARACTERSTICS OF CLOUD TYPES OVER CHAO PHRAYA RIVER BASIN DURING JUNE TO AUGUST BASED ON MTSAT INFRA-RED DATASET
WATANABE Yamato, YAMADA Tomohito, SUSENO Dwi Prabowo Yuga, SAKOLNAKHON Kamol P.N., TONJAN Somkuan, CHAIYASAN Chatchai
PROCEEDINGS OF THE JAPANESE CONFERENCE ON HYDRAULICS, 70, 4, I_313, I_318, Japan Society of Civil Engineers, 2014
Japanese, Chao Phraya river basin is one of the largest basins in the Indochina Peninsula where is located at the South East Asian monsoon region. This study focuses on the diurnal patterns of several cloud types in the rainy season especially during June to August. We used MTSAT (Multi-functional Transport Satellite) Infra-red information from which we classified the clouds into 7 types and then analyzed diurnal characteristics of each cloud type especially in the years 2010 and 2011. 2010 was a drought year and clouds appeared earlier than in the climatology (1996-2011) and 2011, on the other hand, was a flood year and clouds appeared approximately 1 hour later than in the climatology. We obtained results which showed all types of clouds had each diurnal pattern of appearance. Furthermore, those patterns were similar between 2010 and 2011, however they shifted a few hours earlier in 2011 than in 2010.

Atmospheric blocking and its relation with climate changes in the CMIP5 models
KITANO Yoshikazu, YAMADA Tomohito
Proceeding of Annual Conference, 27, 100121, 100121, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2014
Japanese, In middle latitudes, atmospheric blocking is one of the crucial meteorological phenomena. It has a persistent feature leading to extreme events such as heat waves , cold waves , drought and severe precipitation over the surrounding area. The purpose of this study is to reveal the relationship between atmospheric blocking and climate change effects. Mainly, we discuss the change of temperature distribution in mid-latitudes and blocking indexes.

Activity report of a research group JSHWR 2013, "Present and future distributions of specific drought rate in Hokkaido, Japan"
Sakata Yoshitaka, Chikita Kazuhisa, Nakatsukawa Makoto, Yamada Tomohito, Kudo Keisuke, Koike Akio, Hamahara Yoshinari, Kimura Mineki, Usutani Tomohide, Uehara Hiroyuki
Proceeding of Annual Conference, 27, 100049, 100049, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2014
Japanese, We make an oral presentation of activity results of the research group JSHWR 2013, "Present and future distributions of specific drought rate in Hokkaido, Japan." The purpose of this group is to map present and future specific rates at drought periods in Hokkaido, using an amout of hydrologic and climate data, field measurements in no gauging areas, and spatial analyses based on GIS. The main works in 2013 were to prepare the past hydrologic and climate data over the half century, and to convert the data into GIS format. Other works such as GIS and trend analyses were made only on trial. The conferences were held at 27 May 2013, 26 December 2013, and 20 February 20 2014 to discuss the methods and plans for this research.

THE EFFECTS OF VELOCITY AND DENSITY PROFILES ON THE ATMOSPHERIC INTERFACE
Yoshikazu KITANO, Tomohito YAMADA, Norihiro IZUMI
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 70, 4, I_871, I_876, Japan Society of Civil Engineers, 2014, [Peer-reviewed]
Japanese, Scientific journal, Schmid & Henningson discussed the point disturbance in the homogeneous medium of piecewise linear boundary layer using the method of stationary phase. In addition to this study, we include the density profile to consider the inhomogeneous boundary layer like atmospheric boundary layer. We assume first that the fluid is inviscid and incompressible, density being convected but not diffused. Then the fundamental equations are the Navier-Stokes equations, continuity equation and incompressibility equation and we derive the 3-dimentional Taylor-Goldstein equation. Under the Boussinesq approximation, we obtain the exact solution about the point disturbance propagation on the arbitrary horizontal plane. Using internal Froude number, we explain the characteristics of the solutions.

ESTIMATION FOR EXTREME RAINFALL AND SNOWFALL BASED ON RELATIONSHIP BETWEEN DAILY TEMPERATURE AND PRECIPITATION INTENSITY ASSOCIATED WITH THE CLAUSIUS-CLAPEYRON EQUATION
Taiki FUKUSHIMA, Tomohito YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 70, 4, I_529, I_534, Japan Society of Civil Engineers, 2014, [Peer-reviewed]
Japanese, Scientific journal, This paper discussed estimation method of probable maximum value of extreme precipitation. We analyzed the 99th percentile of 10-minutes and 1-hour precipitation for each daily average temperature bin based on observational data in Sapporo. Even if temperature is lower than zero degrees, 99th percentile precipitation intensities tend to have an approximation equation that rate of the precipitation increase was almost same as the Clausius-Clapeyron like relation. We estimated the future 99th percentile rainfall intensity under climate change condition by using the projected future temperature in a dynamically downscaled temperature in the Regional Spectral Model (RSM).

Simultaneous Image Measurement of Sprays and Air Bubbles Formed during Wind Wave Breaking Event
OTSUKA JUN'ICHI, WATANABE YASUNORI, TASHIRO KOKI, OYAMA TAKAHIRO, SARUWATARI AYUMI, YAMADA TOMOHITO
土木学会論文集 B2(海岸工学)(Web), 70, 2, I.41-I.45 (J-STAGE), I_45, Japan Society of Civil Engineers, 2014
Japanese, Sprays and air bubbles formed during wind wave breaking events under various wind conditions were simultaneously visualized using two high-speed video cameras and a back-light imaging technique. The shapes of the sprays and entrained bubbles were quantitatively measured on the basis of novel level-set image detecting algorithm. Spectrum slope of spray and bubble size were found to decrease from approximately 2.2 mm and 1.5 mm respectively. It was also found that the volume rate and wind-wave Reynolds number (RB), the number density and RB are both related to positive correlation.

Modulations of the heat transfer across wind wave surfaces
WATANABE YASUNORI, TASHIRO KOKI, OTSUKA JUN'ICHI, OYAMA TAKAHIRO, YAMADA TOMOHITO
土木学会論文集 B2(海岸工学)(Web), 70, 2, I.56-I.60 (J-STAGE), I_60, Japan Society of Civil Engineers, 2014
Japanese, High speed infrared imaging measurements were performed for identifying mechanical factors to govern surface skin temperatures on wind waves under moderate to strong winds. Surface renewals owing to turbulent disturbances are found to predominantly determine the skin temperature amplitude and phase lags to surface elevation, which is parameterized by a so-called wind-wave Reynolds number (RB). The modulations of the skin temperature variations are observed at RB ~ 4 × 104, indicating governing dynamics to produce surface turbulence is altered at the boundary.

Water Exchange at the Mouth of Tanabe Bay in Kii Peninsula, Japan
UCHIYAMA YUSUKE, MATSUKAWA DAISUKE, KANKI RYOSUKE, BABA YASUYUKI, MORI NOBUHITO, MIZUTANI HIDEAKI, WATANABE YASUNORI, OTSUKA JUN'ICHI, YAMADA TOMOHITO, SARUWATARI AYUMI, NINOMIYA JUN'ICHI
土木学会論文集 B2(海岸工学)(Web), 70, 2, I.446-I.450 (J-STAGE), I_450, Japan Society of Civil Engineers, 2014
Japanese, Tanabe bay is a small embayment connected directly to the Pacific Ocean to the south, whereas frequently suffers from harmful algal blooms due to sewage effluent and the local aquaculture industry. For preserving the ecosystem in the bay, it is necessary to understand an oceanic structure in the bay along with water exchange at the bay entrance. We thus conduct a comprehensive investigation consisting of a shipboard measurement, a season-long platform observation, and a triply nested high-resolution ocean modeling. The water exchange at the bay mouth is largely affected by semi-diurnal tidal currents and episodic subtidal intrusion of the offshore water controlled by mesoscale circulations.

Extreme precipitation intensity in future climates associated with the Clausius-Clapeyron-like relationship
Yamada Tomohito J, Farukh Murad. A, Fukushima Taiki, Inatsu Masaru, Sato Tomonori, Pokhrel Yadu N, Oki Taikan
Hydrological Research Letters, 8, 4, 108, 113, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2014
English, This paper introduces a method named "hybrid-downscaling" to estimate the future extreme hourly precipitation intensity based on observational evidence of the 99th percentile precipitation intensity against air temperature in Sapporo and Tokyo, Japan. The future projected air temperature under the Special Report on Emissions Scenarios (SRES) A1B was used after dynamical downscaling using 3 different regional atmospheric models (RAMs) with lateral boundary conditions from 3 different general circulation models (GCMs). We analyzed the 99th percentile of hourly precipitation intensity against daily mean air temperature in Sapporo and Tokyo. The 99th percentile precipitation intensity tended to have an approximate equation in which the rate of increment was similar to the Clausius-Clapeyron rate of change in the saturated water vapor. This study also showed that the precipitable water vapor and the convective instability followed the Clausius-Clapeyron-like rate of change during the hours with the 99th percentile precipitation intensity.

The role of gps precipitable water vapor and atmosphere stability index in the statistically based rainfall estimation using MTSAT data
Dwi Prabowo Yuga Suseno, Tomohito J. Yamada
Journal of Hydrometeorology, 14, 6, 1922, 1932, Amer meteorological soc, Dec. 2013
English, Scientific journal, A rainfall estimation method was developed based on the statistical relationships between cloud-top temperature and rainfall rates acquired by both the 10.8-μm channel of the Multi-Functional Transport Satellite (MTSAT) series and the Automated Meteorological Data Acquisition System (AMeDAS) C-band radar, respectively. The method focused on cumulonimbus (Cb) clouds and was developed in the period of June-September 2010 and 2011 over the landmass of Japan and its surrounding area. Total precipitable water vapor (PWV) and atmospheric vertical instability were considered to represent the atmospheric environmental conditions during the development of statistical models. Validations were performed by comparing the estimated values with the observed rainfall derived from the AMeDAS rain gauge network and the Tropical Rainfall Measuring Mission (TRMM) 3B42 rainfall estimation product. The results demonstrated that the models that considered the combination of total PWV and atmospheric vertical instability were relatively more sensitive to heavy rainfall than were the models that considered no atmospheric environmental conditions. The use of such combined information indicated a reasonable improvement, especially in terms of the correlation between estimated and observed rainfall. Intercomparison results with the TRMM 3B42 confirmed that MTSAT-based rainfall estimations made by considering atmospheric environmental conditions were more accurate for estimating rainfall generated by Cb cloud. © 2013 American Meteorological Society.

人間活動を考慮した陸面過程モデルの北海道への適用
KONO TAKENORI, KONO TAKENORI, YAMADA TOMOHITO, POKHREL YADU NATH
地球環境研究論文集, 21, 5, I.177-I.182, I_182, Japan Society of Civil Engineers, 17 Sep. 2013
Japanese, Water is a fundamental resource for human sustenance. However, the amount of water that is easily accessible is limited and therefore proper management of water resources is very important to fulfill the increasing demand and hence to maintain the standard of living for the escalating population. Recent studies have shown that human activities such as irrigation and reservoir operation have significantly affected the natural flow systems, and therefore accounting these human factors in the model is critically important to simulated land surface hydrologic processes realistically. Recently an integrated model "MATSIRO with human impacts" was developed by incorporating the human factors into the MATSIRO model. In this study, the global model was applied for Japan with a particular focus on Hokkaido region because Hokkaido is the largest agricultural region in Japan and agriculture accounts for the largest portion of human water use. Using the model, we show how the simulated hydrologic variables such as evapotranspiration and soil temperature are affected due to irrigation.

STUDY ON RUNOFF ANALYSIS CONSIDERING VERTICAL INFILTRATION IN A SLOPE
YOSHIMI Kazuhiro, YAMADA Tadashi
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 69, 5, I_145, I_150, Japan Society of Civil Engineers, 2013, [Peer-reviewed]
Japanese, It is important to clarify the runoff process of catchment water which reached the surface of the ground, and it has been studied intensively in the field of hydrology. In general, it is thought that the runoff phenomenon consists of multiple runoff components. In the past, some runoff models with multi-layer construction are proposed. Although these models' parameters have physical meanings, their reproducibility of hydrograph is not significant. A runoff model based on Kinematic Wave considering infiltration mechanics is newly proposed in this paper. Moreover, this model is applied to the Kusaki dam basin(254km²), and the availability is shown.

Introduction to Radiological Hydrology: A Kinematic Model to Estimate the Effective Dose of Radioactive Substances in the Human Body for Radiological Protection
Tadashi Yamada, Tomohito J. Yamada, Syota Sasaki
PROCEEDINGS OF THE 35TH IAHR WORLD CONGRESS, VOLS I AND II, 356, 368, TSINGHUA UNIV, 2013, [Peer-reviewed]
English, International conference proceedings, The present study provides a readily understandable kinematic-based model to estimate the effective dose of radioactive substances in the human body without the need for consideration of any complicated mechanism. For example, the International Commission on Radiological Protection has developed an exact model, which is considered by radiologists the standard method of calculating the effective dose. However, this method is too complex for non-professional researchers of radiology to understand because it divides a human body into similar to 20 organs. In contrast, here we calculate the effective dose by regarding the human body as a single vessel. Although the present study does not involve consideration of a complicated mechanism, it does provide results with an accuracy equal to those of existing research.

Overestimated water storage Reply
Pokhrel Yadu N, Hanasaki Naota, Yeh Pat J. -F, Yamada Tomohito J, Kanae Shinjiro, Oki Taikan
NATURE GEOSCIENCE, 6, 1, 2, 3, Jan. 2013, [Peer-reviewed]

LAND AND SEA BREEZE ASSOCIATED TEMPERATURE GRADIENT BETWEEN ISHIKARI AREA AND YUHUTSU AREA
FUKUSHIMA TAIKI, YAMADA TOMOHITO, MIYAZAKI SHIN
土木学会論文集 B1(水工学)(Web), 69, 4, I.1759-I.1764 (J-STAGE), I_1764, Japan Society of Civil Engineers, 2013
Japanese, This paper discussed the land and sea breeze circulation (LSBC)between Ishikari and Yuhutsu areas in Hokkaido. The diurnal variation of LSBC during boreal summer(July and August) of 1985-2009 was mainly investigated by using various data. LSBC was observed between Ishikari and Sapporo up to 13km from coastal zones of the Japan Sea. Tomakomai to Atsuma area also showed LSBC around16km from coastal zones of the Pacific Ocean. For inland region that area from Chitose to Naganuma, southerly wind was observed all day long. The reason is related to a fact that this inland region has strong southerly wind associated with the meridional temperature gradient between Ishikari and Yuhutsu area. Thermal balance between SST and temperature of land could be important to control the horizontal scale of LSBC. In the La-Nina years, SST over the Japan Sea at the vicinity of Sapporo area was higher than the climatology, and LSBC was enhanced and expanded its spatial scale.

FREQUENCY OF ATMOSPHERIC BLOCKING ASSOCIATED WITH MERIDIONAL SURFACE TEMPERATURE CHARACTERISTICS IN BOREAL WINTER IN THE MID-LATITUDES
YAMADA Tomohito, HATA Yoshihiro
PROCEEDINGS OF THE JAPANESE CONFERENCE ON HYDRAULICS, 69, 4, I_397, I_402, Japan Society of Civil Engineers, 2013
Japanese, Atmospheric blocking is one of the main causes of extreme meteorological events such as spells of extremely cold weather, heat wave and continuous heavy rainfall in the mid-latitudes. The European Centre for Medium-Range Weather Forecasts Reanalysis Dataset (ERA-40) was analyzed to clarify both the characteristics of the latitudinal surface temperature field and the frequency of atmospheric blocking (FAB) in December, January, and February between 1960 and 1999. In years with a small meridional surface temperature gradient between the low and high latitudes, the FAB was larger than the average for the 40-year climatology, as well as persisting for longer and having a longitudinally larger spatial scale. A noticeable characteristic of these years was a larger dominant eddy scale length at the 500-hPa level compared to the average for the climatology. The amplitude of the dominant eddy scale length was also enhanced.

DOWNSTREAM MIGRATING STEPS ON ICE
NAITO KENSUKE, IZUMI NORIHIRO, YOKOKAWA MIWA, YAMADA TOMOHITO
土木学会論文集 B1(水工学)(Web), 69, 4, I.1123-I.1128 (J-STAGE), I_1128, Japan Society of Civil Engineers, 2013
Japanese, In recent years, cyclic steps are discovered in a variety of environments, such as deep ocean floors and ice floors on planets other than the earth. Water can exists only in the form of ice in the extraterrestrial environments, where temperature is commonly by far lower than that on the earth. Therefore, cyclic steps in the extraterrestrial environments are expected to be often found on ice. In order to obtain basic knowledge on the formation of ice steps, we have performed a series of experiments in a cold room of Institute of Low Temperature Science, Hokkaido University, and reproduced ice steps migrating in the downstream direction. In this paper, we formulated the formation process of ice steps, and provide a reasonable explanation of the downstream migrating ice steps based on the experimental results.

THE CLOUD CLIMATOLOGY OVER SOUTHEASTERN ASIAN REGIONS BY USING MTSAT CLOUD CLASSIFICATION
WATANABE YAMATO, YAMADA TOMOHITO, SUSENO DWI, PRABOWO YUGA
土木学会論文集 B1(水工学)(Web), 69, 4, I.301-I.306 (J-STAGE), I_306, Japan Society of Civil Engineers, 2013
Japanese, There are many extreme hydrometeorological phenomena such as heavy rain and drought events in the world. A considerable shortage of observing stations was motivated us to utilize the remote sensing for observing water resources and related information from space. In this study we used MTSAT (Multi-functional Transport Satellite) to acquire cloud type characteristics. The observation target was the western pacific region. The spatial distribution between MTSAT and JMA(Japan Meteorological Agency) cloud classification showed reasonably good agreement while our result estimated many Cb(Cumulonimbus) focusing on June to September 2010. The Cb cloud was estimated 20 to 60% larger than the 15-year climatology(1996-2010) over northern part of Thailand in 2011.

SUB-SEASONAL HYDROLOGICAL FORECAST SKILLS IN A DROUGHT EVENT ASSOCIATED WITH LAND INITIALIZATIONS INCLUDING HUMAN ACTIVITIES IN AN ATMOSPHERIC GENERAL CIRCULATION MODEL
YAMAHARA KOKI, YAMADA TOMOHITO, POKHREL YADU
土木学会論文集 B1(水工学)(Web), 69, 4, I.1807-I.1812 (J-STAGE), I_1812, Japan Society of Civil Engineers, 2013
Japanese, In recent years, the damage caused by extreme weather events has frequently been reported in many parts of the world. Therefore the improvement of prediction accuracy for extreme events is an urgent issue. This study conducted to evaluate the sub-seasonal forecast skill with land initializations in an Atmospheric General Circulation Model (AGCM) targeting a severe drought event which occurred in the North American continental in boreal summer of 1988. The experiment using land initialization with influence of human activities, sub-seasonal forecast skill for near surface temperature improved its skill comparing with another forecast experiment without realistic land initializations. We obtained the result of forecast that soil moisture states could come to have a long dry state by considering human activities at the drought event.

Seasonal variation of land-atmosphere coupling strength over the West African monsoon region in an atmospheric general circulation model
Tomohito J. Yamada, Shinjiro Kanae, Taikan Oki, Randal D. Koster
Hydrological Sciences Journal, 58, 6, 1276, 1286, Taylor & Francis, 2013
English, Scientific journal, The seasonal variation of land-atmosphere coupling strength has been examined using an extended series of atmospheric general circulation model (AGCM) simulations. In the Western Sahel of Africa, strong coupling strength for precipitation is found in April and May, just prior to and at the beginning of the monsoon season. At this time, heat and water fluxes from the surface are strongly controlled by land conditions, and the unstable conditions in the lower level of the troposphere, as induced by local land state, allow the surface fluxes to influence the variability of convective precipitation-and thus the timing of monsoon onset.Editor Z. W. KundzewiczCitation Yamada, T.J., Kanae, S., Oki, T., and Koster, R.D., 2013. Seasonal variation of land-atmosphere coupling strength over the West African monsoon region in an atmospheric general circulation model. Hydrological Sciences Journal, 58 (6), 1276-1286. © 2013 IAHS Press.

大気密度成層における擾乱の発達過程
KITANO YOSHIKAZU, YAMADA TOMOHITO, IZUMI NORIHIRO
地球環境研究論文集, 20, 5, I.205-I.210, I_210, Japan Society of Civil Engineers, 13 Sep. 2012
Japanese, There are many unknown issues about line-shaped rainbands (LRBs) which is one of the meso-scale meteorological phenomena making torrential rainfall events in Japan. For disaster prevention, it is very important to reveal the formation mechanism of LRBs. In order to know the mechanism, the authors try to examine the instability of the density stratification. In this study, the rainfall and thermodynamic effects are not considered. To simplify the discussion, this theory considers only the up/down motion of the disturbance in the stratified atmosphere. Using this theory, the authors correlate the region of horizontal disturbance and the two parameters which characterize the shape of LRBs, i.e. the Froude number and the rate of density difference.

Diurnal Characteristics of Rainfall over the Contiguous United States and Northern Mexico in the Dynamically Downscaled Reanalysis Dataset (US10)
Tomohito J. Yamada, Myong-In Lee, Masao Kanamitsu, Hideki Kanamaru
JOURNAL OF HYDROMETEOROLOGY, 13, 3, 1142, 1148, AMER METEOROLOGICAL SOC, Jun. 2012
English, Scientific journal, The diurnal characteristics of summer rainfall in the contiguous United States and northern Mexico were examined with the United States reanalysis for 5 years in 10-km horizontal resolution (US10), which is dynamically downscaled from the National Centers for Environmental Prediction National Center for Atmospheric Research (NCEP-NCAR) Global Reanalysis 1 using the Regional Spectral Model (RSM). The hourly precipitation outputs demonstrate a realistic structure in the temporal evolution of the observed rainfall episodes and their magnitudes across the United States without any prescriptions of the observed rainfall to the global reanalysis and the downscaled regional reanalysis. Nighttime rainfall over the Great Plains associated with eastward-propagating, mesoscale convective systems originating from the Rocky Mountains is also represented realistically in US 10, while the original reanalysis and most general circulation models (GCMs) have difficulties in capturing the series of nocturnal precipitation events in summer over the Plains. The results suggest an important role of the horizontal resolution of the model in resolving small-scale, propagating convective systems to improve the diurnal cycle of summer rainfall.

The onset of the West African monsoon simulated in a high-resolution atmospheric general circulation model with reanalyzed soil moisture fields
T. J. Yamada, S. Kanae, T. Oki, Y. Hirabayashi
ATMOSPHERIC SCIENCE LETTERS, 13, 2, 103, 107, WILEY-BLACKWELL, Apr. 2012, [Peer-reviewed]
English, Scientific journal, The simulation of the onset of the West African monsoon (WAM), associated with the northward shift of the Intertropical Convergence Zone (ITCZ) occurring in May, June, and July, is a challenging task for atmospheric general circulation models (AGCMs), because of complex water and energy balance through the land-atmosphere interaction as well as atmospheric processes. We provide evidence that a combination of state-of-the-art global fields of reanalyzed soil moisture anomalies and a sufficiently high-resolution (similar to 50 km) AGCM produces a successful simulation of the northward shift of the ITCZ and the following onset of the WAM in July. Copyright (C) 2011 Royal Meteorological Society

Climatology of line-shaped rainbands over northern Japan in boreal summer between 1990 and 2010
Tomohito J. Yamada, Jun Sasaki, Naoki Matsuoka
ATMOSPHERIC SCIENCE LETTERS, 13, 2, 133, 138, WILEY-BLACKWELL, Apr. 2012, [Peer-reviewed]
English, Scientific journal, Line-shaped rainbands (LRBs) are severe storm events that cause torrential rainfall across the mid-latitudes and are difficult to accurately predict because of their complex physical processes. We examined the occurrence of LRBs in boreal summer in northern Japan over the period 1990-2010. In years with anomalously many LRBs, the development of LRBs over northern Japan was driven by a combined positive anomaly of warm sea-surface temperatures and westerly moisture flux associated with the prominent pattern of the surface pressure anomalies between the main island of Japan and the Sea of Okhotsk. In contrast, the number of LRBs were significantly small with opposite characteristics. Copyright (C) 2012 Royal Meteorological Society

Evolution of the 2011 Tohoku earthquake tsunami on the pacific coast of Hokkaido
Yasunori Watanabe, Yuta Mitobe, Ayumi Saruwatari, Tomohito Yamada, Yasuo Niida
Coastal Engineering Journal, 54, 1, Mar. 2012, [Peer-reviewed]
Scientific journal, A numerical computation of the 2011 Tohoku earthquake tsunami was performed to identify fundamental features of the tsunami evolution along the coast of Hokkaido, Japan. Edge waves formed at multiple locations where the refracted tsunami focused, governing local surface oscillations and regional variations in tsunami height along the Pacific coast of Hokkaido. The computation reasonably reproduced the distribution of surveyed tsunami height as well as the time records of surface elevation recorded at ports in Hokkaido. The major features of the frequency spectrum for the 2011 Tohoku tsunami were identical to those for the 2003 Tokachi-oki earthquake tsunami; inherent local properties of surface oscillation caused by the passage of edge waves existed, determined by the local bathymetry. © 2012 World Scientific Publishing Company and Japan Society of Civil Engineers.

EVOLUTION OF THE 2011 TOHOKU EARTHQUAKE TSUNAMI ON THE PACIFIC COAST OF HOKKAIDO
Yasunori Watanabe, Yuta Mitobe, Ayumi Saruwatari, Tomohito Yamada, Yasuo Niida
COASTAL ENGINEERING JOURNAL, 54, 1, 1250002.1-1250002.17, WORLD SCIENTIFIC PUBL CO PTE LTD, Mar. 2012
English, Scientific journal, A numerical computation of the 2011 Tohoku earthquake tsunami was performed to identify fundamental features of the tsunami evolution along the coast of Hokkaido, Japan. Edge waves formed at multiple locations where the refracted tsunami focused, governing local surface oscillations and regional variations in tsunami height along the Pacific coast of Hokkaido. The computation reasonably reproduced the distribution of surveyed tsunami height as well as the time records of surface elevation recorded at ports in Hokkaido. The major features of the frequency spectrum for the 2011 Tohoku tsunami were identical to those for the 2003 Tokachi-oki earthquake tsunami; inherent local properties of surface oscillation caused by the passage of edge waves existed, determined by the local bathymetry.

2011年7月新潟・福島豪雨時における線状降水帯の形状特性・環境場に関する考察
WADA TAKUYA, YAMADA TOMOHITO, SUSENO YUGA DWI PRABOWO
水工学論文集(CD-ROM), 56, 4, ROMBUNNO.67, I_402, Japan Society of Civil Engineers, 20 Feb. 2012
Japanese, Meteorological characteristics of the formation and environment of the Niigata-Fukushima heavy rainfall on 28~30 July 2011 were studied. Line-shaped rainfall systems were observed by using synthetic radar and Xband MP radar on 29 July at 09~17 and on 30 July at 00~04. The purpose of this study is to classify these events and to reveal the reason why these occur and stagnate. It was found that the former event can be classified as Back Building type while the latter can be classified as Back Building composite type. The development environments were focused by the convergence, relative humidity, wind and temperature by using the Japan Meteorological Agency GPV mesoscale model dataset. Results indicate that convergence area, flow of high-humidity air at 950hpa and incursion of dry-low-temperature air generated the event on 29 July at 09~17. The event on 30 July at 00~04 was generated by the effect of cold air at 400hpa which flowed into high-humidity region.

A STUDY ON THE EFFECTS OF DIFFERENCE FROM RAINFALL PATTERN ON RUNOFF PHENOMENON IN TONE UPPER RIVER BASIN
YOSHIMI Kazuhiro, OKABE Masato, YAMADA Tadashi
Journal of Japan Society of Civil Engineers, Ser. G (Environmental Research), 68, 5, I_255, I_260, Japan Society of Civil Engineers, 2012, [Peer-reviewed]
Japanese, To clarify the effects of difference from rainfall pattern on runoff phenomenon contributes to the further development of the integrated flood control measures by the combination of various conventional flood control methods. Elucidating those effects is very useful to examine flood control plan. In this study, authors made pseudo rainfall patterns based on Typhoon Kathleen in September 1947 in Tone upper river basin and examined the effects of difference from rainfall pattern we created on runoff phenomenon. In consequence, it was indicated that peak discharge at Yattajima point of observation fluctuated from 19000 m³/s to 27000 m³/s depending on rainfall pattern. Furthermore, it was indicated that peak discharge at that point exceeds design flood discharge depending on rainfall pattern.

THE USE OF GEOSTATIONARY BASED RAINFALL ESTIMATION FOR CHARACTERIZING STORM SEVERITY
SUSENO Dwi, Prabowo Yuga, YAMADA Tomohito J
PROCEEDINGS OF THE JAPANESE CONFERENCE ON HYDRAULICS, 68, 4, I_175, I_180, Japan Society of Civil Engineers, 2012
This research deals with the use of geostationary satellite based rainfall estimation for characterizing storm severity. The objectives of this research are to estimate storm rainfall intensity by using Multi-functional Transport Satellite (MTSAT) blended with C-band rainfall radar data and to show the severity of the identified storm rainfall intensity by representing its return period map. A regional frequency analysis (RFA) method developed by Hosking and Wallis (1997) is used to define the frequency distribution of long-term hourly maximum rainfall over Hokkaido Island. RFA indicates that Generalized Normal/Log Normal three parameters (GNO/LN3) is suitable to describe the frequency distribution of long-term hourly maximum rainfall over Hokkaido Island. Characterization of severity of 24 August 2010 storm event has been performed over Ishikari river basin, Hokkaido according to estimated rainfall using MTSAT data. Even though the return period map shows underestimation in comparison with the current situation of flood event in Ishikari river basin, this information is useful for flood control and mitigation.

Two-dimensional, threshold-based cloud type classification using MTSAT data
Dwi Prabowo Yuga Suseno, Tomohito J. Yamada
REMOTE SENSING LETTERS, 3, 8, 737, 746, TAYLOR & FRANCIS LTD, 2012
English, Scientific journal, A new two-dimensional threshold diagram (2D-THR) has been developed based on maximum likelihood cloud classification results, which can readily be applied for Multi-functional Transport Satellite (MTSAT) split window datasets. Because 2D-THR was trained using northern summer 2010 data for Japan and its surrounding area, it is typically suitable only for summer. Comparison of snapshot cloud type distributions showed that 2D-THR images and the corresponding night-time microphysical colour composite images as well as 2D-THR images and Japan Meteorological Agency (JMA) cloud type images are in good agreement. A time series inter-comparison of the hourly 2D-THR cloud classification results with the JMA cloud type classification data product was performed by calculating spatial correlation of cloud percentage for 1 degrees x 1 degrees grid cells. For cumulonimbus, high-level, middle-level and low-level clouds over tropical and subtropical areas in the northwestern Pacific Ocean region, the spatial correlation between 2D-THR and JMA is moderate. Thus, 2D-THR cloud classification algorithm can be applied in both regions.

Application of adaptive mesh refinement to tsunami computation
Yasunori Watanabe, Yuta Mitobe, Yasuo Niida, Tomohito Yamada
Proceedings of the International Offshore and Polar Engineering Conference, 218, 223, 19 Sep. 2011
International conference proceedings, Adaptive mesh refinement (AMR) is one of the powerful computational tools to enhance local computing resolution at less cost. In this paper, computational performances of AMR for tsunami computer simulations were examined in terms of the accuracy and computational cost through computational tests for long wave propagation initiated by collapse of a water column on still water. AMR was also applied to a practical tsunami evolution - 2003 Tokachi-oki earthquake tsunami, which was compared with observed water elevation for examining the applicability of this method to practical tsunami events. It was found through the numerical tests that the present method is capable of efficiently performing reliable computations of tsunami propagation at high resolution. Copyright © 2011 by the International Society of Offshore and Polar Engineers (ISOPE).

東京における120年時間降雨量データを用いたひと雨降雨形態の日変化形の検討
WADA TAKUYA, YAMADA TOMOHITO
水工学論文集(CD-ROM), 55, 4, ROMBUNNO.81, I_486, Japan Society of Civil Engineers, 22 Feb. 2011
Japanese, Various problems concerning the global environment such as climate change, urbanization, and the heat island phenomenon are paid to attention, especially in terms of rainfall characteristics. This paper focused on characteristics of diurnal patterns of rainfall at Tokyo (Ohtemachi) based on 120-years hourly data from 1890 to 2008. Diurnal patterns were analyzed by using the "P/D" diagnostics which indicates the shape of a single rainfall event by the peak rainfall amount and its duration (whole duration). The P/D diagnostics showed the intensification of short-time rainfall amount in recent. In addition, we proposed a new "P/D" diagnostics which indicates the shape of a single rainfall event with the peak rainfall amount and its duration (from the starting time to the peak time). The results we obtained are following. 1) There is an increasing tendency in the short-time afternoon rainfall. 2) The duration to reaching peak amount for each single rainfall event is clearly decreased particularly at 15LST and 19LST in the recent two decades.

DIURNAL VARIATION OF RAINFALL PROFILES BASED ON 120YEARS HOURLY DATA AT TOKYO
Takuya WADA, Tomohito YAMADA
Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering), 67, 4, I_481, I_486, Japan Society of Civil Engineers, 2011, [Peer-reviewed]
Scientific journal

HYDROLOGICAL FORECAST SKILL ASSOCIATED WITH LAND SURFACE INITIALIZATIONS
YAMADA TOMOHITO J, KOSTER RANDAL D, KANAE SHINJIRO, OKI TAIKAN
水工学論文集(CD-ROM), 54, ROMBUNNO.56, 22 Feb. 2010
English

HYDRAULIC EXPERIMENTS ON RIVER BED TERRAIN IN RIVERMOUTH
aikawa makoto, Qian chaochao, igarashi gou, ichiki shintarou, yamada tadashi
Proceeding of Annual Conference, 23, 87, 87, THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, 2010
Japanese, 河口部では，河川流，沿岸流，潮汐流，波浪など様々な流れが混在しており，非常に複雑な流れをしていることが一般的に知られている．これらの流れにより河口部の河床では，複雑な河床変動が生じており，河床の形成や発達の解明は困難である．よって本研究では沿岸流，潮汐流，波浪といった条件を除き河川流に着目した水理実験を行った．本実験は下流端水位や流量の条件を変化させ，河川流が河床の形成及び流速への影響を明らかにすることを目的とする．

Estimation of predictability with a newly derived index to quantify similarity among ensemble members
Tomohito J. Yamada, Randal D. Koster, Shinjiro Kanae, Taikan Oki
MONTHLY WEATHER REVIEW, 135, 7, 2674, 2687, AMER METEOROLOGICAL SOC, Jul. 2007
English, Scientific journal, This study reveals the mathematical structure of a statistical index, Omega, that quantifies similarity among ensemble members in a weather forecast. Previous approaches for quantifying predictability estimate separately the phase and shape characteristics of a forecast ensemble. The diagnostic Omega, on the other hand, characterizes the similarity (across ensemble members) of both aspects together with a simple expression. The diagnostic Omega is thus more mathematically versatile than previous indices.

夏季インドモンスーン域における降水予測可能性
YAMADA TOMOHITO, KANAE SHINJIRO, OKI TAIKAN
水工学論文集(CD-ROM), 51, ROMBUNNO.53, 318, Japan Society of Civil Engineers, 22 Feb. 2007
Japanese, The predictability of the Indian summer monsoon is examined from an ensemble of 16 atmospheric general circulation model simulations with prescribed sea surface temperatures (SST). The predictability is estimated with a statistical index (Ω) to quantify similarity among the ensemble members. The model simulations show that the predictability of precipitation and the low-level moisture flux during May and June are much larger than that in July and August. The role of land-atmosphere interaction is also focused. During May and June the predictability of soil moisture and near surface temperature are increased by large predictability of precipitation. At the same time, the predictability of cumulus type precipitation could be improved or maintained by positive feedback of large predictability of soil moisture and near surface temperature through atmospheric instability in atmospheric boundary layer. Finally, we suggest two new statistical methods to estimate the phase and shape predictability, and discuss the monthly change of the predictability of the Indian summer monsoon using 3 types of predictability including Ω.

GLACE: The Global Land-Atmosphere Coupling Experiment. Part II: Analysis
Zhichang Guo, Paul A. Dirmeyer, Randal D. Koster, Gordon Bonan, Edmond Chan, Peter Cox, C. T. Gordon, Shinjiro Kanae, Eva Kowalczyk, David Lawrence, Ping Liu, Cheng-Hsuan Lu, Sergey Malyshev, Bryant McAvaney, J. L. McGregor, Ken Mitchell, David Mocko, Taikan Oki, Keith W. Oleson, Andrew Pitman, Y. C. Sud, Christopher M. Taylor, Diana Verseghy, Ratko Vasic, Yongkang Xue, Tomohito Yamada
JOURNAL OF HYDROMETEOROLOGY, 7, 4, 611, 625, AMER METEOROLOGICAL SOC, Aug. 2006
English, Scientific journal, The 12 weather and climate models participating in the Global Land-Atmosphere Coupling Experiment ( GLACE) show both a wide variation in the strength of land-atmosphere coupling and some intriguing commonalities. In this paper, the causes of variations in coupling strength-both the geographic variations within a given model and the model-to-model differences-are addressed. The ability of soil moisture to affect precipitation is examined in two stages, namely, the ability of the soil moisture to affect evaporation, and the ability of evaporation to affect precipitation. Most of the differences between the models and within a given model are found to be associated with the first stage-an evaporation rate that varies strongly and consistently with soil moisture tends to lead to a higher coupling strength. The first-stage differences reflect identifiable differences in model parameterization and model climate. Intermodel differences in the evaporation-precipitation connection, however, also play a key role.

GLACE: The Global Land-Atmosphere Coupling Experiment. Part I: Overview
Randal D. Koster, Zhichang Guo, Paul A. Dirmeyer, Gordon Bonan, Edmond Chan, Peter Cox, Harvey Davies, C. T. Gordon, Shinjiro Kanae, Eva Kowalczyk, David Lawrence, Ping Liu, Cheng-Hsuan Lu, Sergey Malyshev, Bryant McAvaney, Ken Mitchell, David Mocko, Taikan Oki, Keith W. Oleson, Andrew Pitman, Y. C. Sud, Christopher M. Taylor, Diana Verseghy, Ratko Vasic, Yongkang Xue, Tomohito Yamada
JOURNAL OF HYDROMETEOROLOGY, 7, 4, 590, 610, AMER METEOROLOGICAL SOC, Aug. 2006
English, Scientific journal, The Global Land-Atmosphere Coupling Experiment ( GLACE) is a model intercomparison study focusing on a typically neglected yet critical element of numerical weather and climate modeling: land atmosphere coupling strength, or the degree to which anomalies in land surface state ( e. g., soil moisture) can affect rainfall generation and other atmospheric processes. The 12 AGCM groups participating in GLACE performed a series of simple numerical experiments that allow the objective quantification of this element for boreal summer. The derived coupling strengths vary widely. Some similarity, however, is found in the spatial patterns generated by the models, with enough similarity to pinpoint multimodel "hot spots" of land-atmosphere coupling. For boreal summer, such hot spots for precipitation and temperature are found over large regions of Africa, central North America, and India; a hot spot for temperature is also found over eastern China. The design of the GLACE simulations are described in full detail so that any interested modeling group can repeat them easily and thereby place their model's coupling strength within the broad range of those documented here.

An Outline of Heavy Rainfall Disasters in Hidaka Region, Hokkaido Caused by Typhoon No.10 in 2003
Hasegawa, K, T.Araya, T. Ogawa, S. Kikuchi, M. Kuroki, T. Komatsu, H. Saga, Y. Shimizu, O. Shimizu, H. Suzuki, Y. Suzuki, G. Tanaka, S. Tohma, M. Nakatsugawa, S. Hatta, Y. Murakami, T. Yamashita, T. Yamada, Y. Watanabe, Y. Watanabe, M. Fujita
Journal of Hydroscience and Hydraulic Engineering, 24, 1, 41, 56, May 2006, [Peer-reviewed]
English

Influence of "realistic" land surface wetness on predictability of seasonal precipitation in boreal summer
S Kanae, Y Hirabayashi, T Yamada, T Oki
JOURNAL OF CLIMATE, 19, 8, 1450, 1460, AMER METEOROLOGICAL SOC, Apr. 2006
English, Scientific journal, Outputs from two ensembles of atmospheric model simulations for 1951-98 define the influence of "realistic" land surface wetness on seasonal precipitation predictability in boreal summer. The ensembles consist of one forced with observed sea surface temperatures (SSTs) and the other forced with realistic land surface wetness as well as SSTs. Predictability was determined from correlations between the time series of simulated and observed precipitation. The ratio of forced variance to total variance determined potential predictability. Predictability occurred over some land areas adjacent to tropical oceans without land wetness forcing. On the other hand, because of the chaotic nature of the atmosphere, considerable parts of the land areas of the globe did not even show potential predictability with both land wetness and SST forcings.
The use of land wetness forcing enhanced predictability over semiarid regions. Such semiarid regions are generally characterized by a negative correlation between fluxes of latent heat and sensible heat from the land surface, and are "water-regulating" areas where soil moisture plays a governing role in land-atmosphere interactions. Actual seasonal prediction may be possible in these regions if slowly varying surface conditions can be estimated in advance. In contrast, some land regions (e.g., south of the Sahel, the Amazon, and Indochina) showed little predictability despite high potential predictability. These regions are mostly characterized by a positive correlation between the surface fluxes, and are "radiation-regulating" areas where the atmosphere plays a leading role. Improvements in predictability for these regions may require further improvements in model physics.

相似性を示す統計指標の数学的構造
YAMADA TOMOHITO, KANAE SHINJIRO, OKI TAIKAN
水工学論文集, 49, 1, 1, 6, Japan Society of Civil Engineers, 01 Feb. 2005
Japanese, It is shown that a similarity parameter has new mathematical structure. Heretofore, the correlation coefficient is used for quantifying the correlation relationship between two ensemble members. Koster et al<SUP>1</SUP> introduced a statistical parameter, called Ω to quantify the similarity among several ensemble members with calculating the ensemble numbers and the two types of variances. However the mathematical structure of Ω had not been revealed in their studies. The present authors applied to derivate Ω for understanding the mathematical meaning of it. As results, we could have a knowledge that Ω consists of mainly two terms. One is the average value of cross correlation coefficients (ACCC) across all ensemble members. Another is the similarity of the mean value and the variance across all ensemble members. Therfore, the authorscan conclude that Ω shows the similarity of the 'shape' of all ensemble members and the mathematical characteristics is more capacious than the correlation coefficient. The paper ends with some remarks on the mathematical characteristics of 'as a new evaluation methodology for the predictabity of numerical forecast.' in monthly or seasonal time scale.

Contribution of land surface states to precipitation variability in boreal summer with an atmospheric general circulation model　　　　　　　　　　　　　　　
Tomohito Yamada, Shinjiro Kanae, Taikan Oki
85th AMS Annual Meeting, American Meteorological Society - Combined Preprints, 1833, 1843, 2005
English, International conference proceedings

Regions of strong coupling between soil moisture and precipitation
RD Koster, PA Dirmeyer, ZC Guo, G Bonan, E Chan, P Cox, CT Gordon, S Kanae, E Kowalczyk, D Lawrence, P Liu, CH Lu, S Malyshev, B McAvaney, K Mitchell, D Mocko, T Oki, K Oleson, A Pitman, YC Sud, CM Taylor, D Verseghy, R Vasic, YK Xue, T Yamada
SCIENCE, 305, 5687, 1138, 1140, AMER ASSOC ADVANCEMENT SCIENCE, Aug. 2004, [Peer-reviewed]
English, Scientific journal, Previous estimates of land-atmosphere interaction (the impact of soil moisture on precipitation) have been limited by a lack of observational data and by the model dependence of computational estimates. To counter the second limitation, a dozen climate-modeling groups have recently performed the same highly controlled numerical experiment as part of a coordinated comparison project. This allows a multimodel estimation of the regions on Earth where precipitation is affected by soil moisture anomalies during Northern Hemisphere summer. Potential bene its of this estimation may include improved seasonal rainfall forecasts.

大気大循環モデルにおける大気陸面過程相互作用の比較分析
YAMADA TOMOHITO, KANAE SHINJIRO, OKI TAIKAN
水工学論文集, 48, 1, 223, 228, Japan Society of Civil Engineers, 01 Feb. 2004
Japanese, The extent of the coupling strength between the land and the atmosphere controls the behavior of the atmospheric processes. Precipitation is induced by the soil moisture variation. K02 focused on the coupling strength between four AGCMs. It is mentioned that the coupling strength has much model dependence. The authors are participating the GLACE (Global Land-Atmosphere Coupling Experiment) which follows the K02 experiment. Before undertaking the GLACE experiment, it is conducted the K02 experiment to compare or evaluate our AGCM (CCSR/NIES) result with K02 results. As a result, the coupling strength on the precipitation process is much weaker than the latent heat flux. This is the same characteristics in three of four models in other K02 participants. Moreover, the coupling strength on the latent heat flux shows the relatively high value over the Central Eurasia or the North America.

大量アンサンブル気候予測データを用いた風向別風速極値の将来変化の分析
北野慈和, 大庭雅道, 早田直広, 服部康男, 星野剛, 山田朋人, 日本気象学会大会講演予稿集(CD-ROM), 121, 2022

厚真川小流域の崩壊斜面からの流出土砂の観測及び厚真川流域における地震前後の土砂侵食リスクの定量的な評価—北海道胆振東部地震における厚真川流域の土砂災害に関する分野横断型調査研究
宮崎 功太郎, 星野 剛, 山田 朋人, 泉 典洋, 土田 宏一, 研究所紀要 / [北海道河川財団] [編], 32, 184, 202, Dec. 2021
北海道河川財団, Japanese

厚真川山地小流域を対象とした水・土砂流出および地形特性—Characteristics of runoff, sediment transport and topography over the sub-catchment in Aduma river basin—北海道胆振東部地震における厚真川流域の土砂災害に関する分野横断型調査研究
宮崎 功太郎, 星野 剛, 山田 朋人, 泉 典洋, 橋場 雅弘, 研究所紀要 / [北海道河川財団] [編], 31, 179, 197, Dec. 2020
北海道河川財団, Japanese

観測・予測の不確実性と河川流量・水位の関係
山田正, 吉見和紘, 吉見和紘, 山田朋人, 気象研究ノート, 236, 2018

SEASONAL VARIABILITY OF WATER EXCHANGE AT THE ENTRNCE OF A SEMI-ENCLOSE BAY AND ITS UNDERLYING MECHANISMS
岡田信瑛, 内山雄介, 多田拓晃, 遠藤颯, 馬場康之, 水谷英朗, 久保輝広, 森信人, 渡部靖憲, 大塚淳一, 山田朋人, 猿渡亜由未, 二宮順一, 土木学会論文集 B2(海岸工学)(Web), 74, 2, 2018

RESPONSE OF THE OCEAN SURFACE LAYER WITH BREAKING WAVES IN FETCH-LIMITED WIND CONDITIONS
猿渡亜由未, 坂川諒太, 大塚淳一, 馬場康之, 久保輝広, 水谷英朗, 二宮順一, 山田朋人, 内山雄介, 森信人, 渡部靖憲, 土木学会論文集 B2(海岸工学)(Web), 74, 2, 2018

第48回メソ気象研究会・気象災害委員会研究会の報告
佐藤友徳, 山田朋人, 金田幸恵, 横井覚, 筆保弘徳, 時岡真治, 天気, 65, 591, 595, 2018, [Peer-reviewed]

Modeling large-scale human alteration of land surface hydrology and climate
Yadu N. Pokhrel, Farshid Felfelani, Sanghoon Shin, Tomohito J. Yamada, Yusuke Satoh, Geoscience Letters, 4, 1, Dec. 2017, [Peer-reviewed]
Rapidly expanding human activities have profoundly affected various biophysical and biogeochemical processes of the Earth system over a broad range of scales, and freshwater systems are now amongst the most extensively altered ecosystems. In this study, we examine the human-induced changes in land surface water and energy balances and the associated climate impacts using a coupled hydrological–climate model framework which also simulates the impacts of human activities on the water cycle. We present three sets of analyses using the results from two model versions—one with and the other without considering human activities
both versions are run in offline and coupled mode resulting in a series of four experiments in total. First, we examine climate and human-induced changes in regional water balance focusing on the widely debated issue of the desiccation of the Aral Sea in central Asia. Then, we discuss the changes in surface temperature as a result of changes in land surface energy balance due to irrigation over global and regional scales. Finally, we examine the global and regional climate impacts of increased atmospheric water vapor content due to irrigation. Results indicate that the direct anthropogenic alteration of river flow in the Aral Sea basin resulted in the loss of ~510 km3 of water during the latter half of the twentieth century which explains about half of the total loss of water from the sea. Results of irrigation-induced changes in surface energy balance suggest a significant surface cooling of up to 3.3 K over 1° grids in highly irrigated areas but a negligible change in land surface temperature when averaged over sufficiently large global regions. Results from the coupled model indicate a substantial change in 2 m air temperature and outgoing longwave radiation due to irrigation, highlighting the non-local (regional and global) implications of irrigation. These results provide important insights on the direct human alteration of land surface water and energy balances, highlighting the need to incorporate human activities such as irrigation into the framework of global climate models and Earth system models for better prediction of future changes under increasing human influence and continuing global climate change., Springer Science and Business Media LLC, English

確率限界法検定に基づく確率水文量の信頼区間に関する研究
清水 啓太, 山田 正, 山田 朋人, 地球環境シンポジウム講演集, 25, 101, 106, Sep. 2017
土木学会, Japanese

Field Measurements at Tanabe-Nakashima Observation Tower in the Summer of 2016
馬場康之, 水谷英朗, 久保輝広, 内山雄介, 森信人, 渡部靖憲, 山田朋人, 猿渡亜由未, 大塚淳一, 二宮順一, 京都大学防災研究所年報(CD-ROM), 60, 664‐671, Sep. 2017
Japanese

ディスドロメータを用いた野外飛沫観測
岡地寛季, 山田朋人, 渡部靖憲, 猿渡亜由未, 大塚淳一, 森信人, 馬場康之, 水谷英朗, 久保輝広, 二宮順一, 内山雄介, 土木学会北海道支部論文報告集(CD-ROM), 73, ROMBUNNO.B‐04, Feb. 2017
Japanese

Uncertainty of Rainfall Amount and River Discharge in Mountainous Catchments Associated with Spatial Distribution of Rainfall Observation and Meteorological Prediction
小林 彩佳, 岡地 寛季, グエンレ ズン, 山田 朋人, 地球環境研究論文集 = Global environment engineering research : 地球環境シンポジウム, 25, 63, 69, 2017
土木学会, Japanese

Determination of Sea Spray Droplet Distribution Under Marine Observation and Wind Tunnel Experiment
OKACHI Hiroki, YAMADA Tomohito, Watanabe Yasunori, OOTSUKA Junichi, Proceeding of Annual Conference, 30, 0, 95, 95, 2017
海面由来の砕破飛沫に着目した研究では，大気海洋間での運動量・熱交換に与える飛沫の影響が議論されている．現在，海面抵抗は風速が大きくなるにつれて増加するとされている．しかし風速30m/s以上の暴風下では発達した風波と海表面上に分布する砕破飛沫の影響により海面の抵抗が著しく低下-若しくは一定になるという提案がある．砕破飛沫は蒸発することで周りの大気から潜熱を奪う冷却効果を持つ．潜熱を吸収し温度上昇した飛沫が海面に落下することで海面水温を上昇させる．このプロセスにより飛沫が大気海洋間の熱交換に影響を与える．この過程を解明するために飛沫観測する必要があるが，暴風雨下では降雨を伴うため飛沫の物理過程の解明は困難である．一方で雨滴に着目をすると，海洋及び陸での降雨観測は地球全体の水循環を把握するために不可欠である．しかし海洋観測では降雨のみならず砕破飛沫の混合が考えられる．そのため飛沫及び降雨の研究において両者を分類することは不可欠である．本研究では和歌山県田辺湾沖での雨滴及び砕破飛沫の直接観測と砕破飛沫の室内風洞実験を試みた．<br /> 野外観測では雨滴と砕破飛沫の混合したデータから両者を分類し，砕破飛沫の粒径分布を抽出した．また降雨時の粒径分布では風速の増加と共に飛沫の影響と考えられる1mm以下の粒径を持つ粒子数の増加が確認できた．室内実験からは風速が増加するに連れて粒子数の増加，体積の増加，運動量交換に寄与する抵抗係数の減少が確認できた．, 水文・水資源学会, Japanese

Field Measurements at Tanabe-Nakashima Observation Tower in the Summer of 2015
馬場康之, 水谷英朗, 久保輝広, 内山雄介, 森信人, 渡部靖憲, 山田朋人, 猿渡亜由未, 大塚淳一, 二宮順一, 京都大学防災研究所年報(CD-ROM), 59, ROMBUNNO.59B,41, Sep. 2016
Japanese

WRFを用いた降雨再現実験において微物理過程および初期条件の感度分析
盧 涛, 山田 朋人, 山田 正, 地球環境シンポジウム講演集, 24, 99, 101, Aug. 2016
土木学会, Japanese

水惑星条件下における海表面温度変化に対する極端現象の応答
一瀬 輪子, 北野 慈和, 山田 朋人, 地球環境シンポジウム講演集, 24, 141, 143, Aug. 2016
土木学会, Japanese

底面に冷熱源を持つ回転水槽実験における回転初期の遷移過程と高さ依存性
一瀬輪子, 北野慈和, 山田朋人, 渡部靖憲, 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 72, 2016

底面摩擦を考慮した円形跳水現象の定式化
有雅正修, 山田朋人, 横川美和, 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 72, 2016

氷界面波が形成する密度流の速度分布と温度分布測定の試み
長谷川貴士, 角田尭史, 泉典洋, 横川美和, 山田朋人, 土木学会北海道支部論文報告集(CD-ROM), 72, 2016

氷床上を流れるカタバ風の流速および温度の測定実験
角田尭史, 長谷川貴士, 泉典洋, 横川美和, 山田朋人, 土木学会北海道支部論文報告集(CD-ROM), 72, 2016

氷上のステップ地形の発達:理論解析とアナログ実験の比較
横川美和, 泉典洋, 内藤健介, PARKER Gary, 山田朋人, GREVE Ralf, 日本堆積学会大会プログラム・講演要旨, 2016, 2016

気候変動への対応を視野に入れた盛土内水位予測モデルの開発
西村聡, 所哲也, 泉典洋, 山田朋人, 地盤工学研究発表会発表講演集(CD-ROM), 51st, 2016

Marine observation with disdrometer under strong wind condition
Okachi Hiroki, Yamada Tomohito, Watanabe Yasunori, Saruwatari Alum, Otuka Junichi, Mori Nobuhito, Baba Yasuyuki, Mizutani Hideaki, Kubo Teruhiko, Ninomiya Junnichi, Uchiyama Yuusuke, Proceeding of Annual Conference, 29, 0, 35, 35, 2016
Associated with global warming, the effects of sea level rise are linked to frequency and intensity of storms and other weather events. Previous researches argue that sea spray affects the development of typhoons. This study reports a marine observation on Tanabe bay near Wakayama Prefecture utilizing a measurement instrument called parsivel. Parsivel can detect the diameter of a droplet and the distribution of velocity. In our observation point, we reveal the presence of spray droplets with 1.5mm ~ 5.510mm diameter when typhoon events occurs in 2015. We discuss the relationship between sea spray and wind velocity when storm events occurs.<br>, 水文・水資源学会, Japanese

ディスドロメータを用いた飛沫粒径分布の風速及び高度依存性
岡地寛季, 山田朋人, 渡部靖憲, 猿渡亜由未, 大塚淳一, 馬場康之, 水谷英朗, 久保輝広, 二宮順一, 内山雄介, 森信人, 地球環境シンポジウム講演集, 23rd, 149, 150, 02 Sep. 2015
Japanese

北海道における融雪土砂災害の危険性の現状と将来予測
松岡 直基, 山田 朋人, 中林 宏典, 地球環境シンポジウム講演集, 23, 47, 50, Sep. 2015
土木学会, Japanese

火星北極冠における円形跳水現象
有雅 正修, 山田 朋人, 泉 典洋, 地球環境シンポジウム講演集, 23, 197, 201, Sep. 2015
土木学会, Japanese

北半球における夏季のブロッキング現象が極端高温日に与える影響
布川 敦士, 北野 慈和, 山田 朋人, 地球環境シンポジウム講演集, 23, 151, 153, Sep. 2015
土木学会, Japanese

Field Measurements at Tanabe-Nakashima Observation Tower in the Summer of 2014
馬場康之, 水谷英朗, 久保輝広, 内山雄介, 森信人, 渡部靖憲, 山田朋人, 猿渡亜由未, 大塚淳一, 二宮順一, 京都大学防災研究所年報(CD-ROM), 58, ROMBUNNO.58B,36, 320, Sep. 2015
京都大学防災研究所, Japanese

将来の短時間豪雨の推定と降雨の不確実性 : 北海道を対象とする総合的ダウンスケール手法の開発と適用 (特集 地域で動き出す気候変動への"適応")
山田 朋人, 生活と環境, 60, 7, 39, 44, Jul. 2015
日本環境衛生センター, Japanese

THE EFFECT OF THE SPATIAL DISTRIBUTION OF RAINFALL IN TONE UPPER BASIN ON THE DISCHARGE IN RUNOFF PHENOMENA
Shimizu Yuta, Yoshimi Kazuhiro, Yamada Tadashi, Proceeding of Annual Conference, 28, 100106, 2015
The track of each typhoon follows different traces. And the rainfall characteristics of each typhoon such as the occurrence time of the peak are also different. Even if supposing the typhoon of the same scale came again, it may not trace the same track. The rainfall characteristics like the spatial distribution of the rainfall may not be same. In other words, the water level may be beyond a high water level by the spatial difference of rainfall pattern in spite of being the same scale as a past typhoon. In this study, it was aimed at explicating how the spatial distribution of rainfall will affect the discharge in a basin. As the object of Kathleen typhoon that brought the most damage in the past in Tone River basin., THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

降雨の不確実性に起因する流出高の不確実性の時間発展を記述したFokker-Planck方程式に関する基礎的研究
吉見和紘, 諸岡良優, 山田正, 山田朋人, 地球環境シンポジウム講演集, 23rd, 2015

底面の加熱および冷却を伴う回転流体水槽実験
一瀬輪子, 山田朋人, 北野慈和, 渡部靖憲, 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 71, 2015

回転する水路に形成されるサイクリックステップ
有雅正修, 山田朋人, 横川美和, 泉典洋, 土木学会北海道支部論文報告集(CD-ROM), 71, 2015

カタバ風によって流れ-氷界面に形成される界面波
角田尭史, 石黒友紀, 泉典洋, 横川美和, 山田朋人, 土木学会北海道支部論文報告集(CD-ROM), 71, 2015

氷上を流れる流体による界面波の形成実験
石黒友紀, 角田尭史, 泉典洋, 横川美和, 山田朋人, 土木学会北海道支部論文報告集(CD-ROM), 71, 2015

CHARACTERISTICS OF RAINFALL AND TYPHOONS IN SOUTHEAST ASIA ASSOCIATED WITH LARGE-SCALE SEA SURFACE TEMPERATURE ANOMALIES
小林 彩佳, 山田 朋人, 竹内 大輝, 地球環境研究論文集 = Global environment engineering research : 地球環境シンポジウム, 23, 263, 268, 2015
土木学会, Japanese

THE RELATIONSHIP BETWEEN NORTHEASTWARD SHIFT OF WINTER BLOCKING OVER THE NORTH PACIFIC AND DISTRIBUTION OF EXTREME LOW TEMPERATURE DAYS OVER SURROUNDING JAPAN UNDER FUTURE CLIMATES
北野 慈和, 山田 朋人, 地球環境研究論文集 = Global environment engineering research : 地球環境シンポジウム, 23, 177, 182, 2015
土木学会, Japanese

P222 北海道における気候変動適応研究のための水文・気象ダウンスケールデータの情報公開ツール「近未来ビューワ」の開発(ポスターセッション)
小松 麻美, 小倉 勉, 松岡 直基, 佐藤 隆光, 山田 朋人, 稲津 將, 佐藤 友徳, 大会講演予講集, 107, 253, 253, 2015
日本気象学会, Japanese

P224 CMIP5マルチモデルを用いたブロッキング発生頻度と極端現象の発生位置の変遷(ポスターセッション)
北野 慈和, 山田 朋人, 大会講演予講集, 107, 255, 255, 2015
日本気象学会, Japanese

P231 北パキスタンにおける豪雨発生時の大規模気象場の特徴(ポスターセッション)
竹内 大輝, 山田 朋人, Fantkh Murad A., 大会講演予講集, 107, 262, 262, 2015
日本気象学会, Japanese

P312 「超高解像度観測と数値モデルによる大雪や突風をもたらす降雪雲の動態に関する研究」の概要紹介(ポスター・セッション)
山田 芳則, 藤吉 康志, 山田 朋人, 佐藤 友徳, 牛尾 智雄, 南雲 信宏, 大会講演予講集, 107, 330, 330, 2015
日本気象学会, Japanese

P236 底面からの加熱及び冷却を伴う回転水槽実験(ポスターセッション)
北野 慈和, 一瀬 輪子, 山田 朋人, 渡部 靖憲, 泉 典洋, 大会講演予講集, 107, 267, 267, 2015
日本気象学会, Japanese

北海道における夏季気候変動に関するマルチGCM×マルチRAM実験による力学的ダウンスケーリング
INATSU MASARU, SATO TOMONORI, YAMADA TOMOHITO, KUNO RYUSUKE, SUGIMOTO SHIORI, FARUKH M.A, POKHREL YADU N, KURE SHUICHI, 日本気象学会大会講演予稿集, 106, 106, 125, 125, 30 Sep. 2014
日本気象学会, Japanese

マルチGCM‐マルチRAMダウンスケーリング実験による北海道の冬季気候予測の不確実性評価
SATO TOMONORI, INATSU MASARU, YAMADA TOMOHITO, KUNO RYUSUKE, SUGIMOTO SHIORI, FARUKH M.A, POKHREL Y.N, KURE SHUICHI, 日本気象学会大会講演予稿集, 106, 106, 477, 477, 30 Sep. 2014
日本気象学会, Japanese

パキスタンに豪雨をもたらすインドモンスーンの蛇行パターン及びブロッキングの特徴
TAKEUCHI DAIKI, YAMADA TOMOHITO, FARUKH MURAD AHMED, 地球環境研究論文集, 22, 5, I.263-I.269, I_269, 03 Sep. 2014
Pakistan experienced an extreme rainfall event in July to August 2010. Two of the major contributing factors behind this extreme event were upper level stagnant blocking over western Russia and meandering pattern of Indian monsoon. In this study, monsoon patterns were identified. The kind of monsoon pattern that affected 2010 Pakistan flood consists of 64% of total flooding events in Pakistan. We focus on sea level pressure anomaly on 3 identified patterns of monsoon meandering. In 2010 Pakistan flooding case, the sea level pressure anomaly over the Middle East was lower, whereas, the anomaly over Northwestern Russia was higher. Moreover, 2010 Pakistan flooding case was affected by stagnant upper level (500hPa) blocking to descend cold air from Siberia to Pakistan. The number of monsoon meandering pattern which affects Pakistan flood tended to increase from June to August. On the other hand, the number of simultaneous occurrence of upper level blocking tended to decrease from June to August., Japan Society of Civil Engineers, Japanese

MTSAT近赤外放射情報を用いた夏季のチャオプラヤ川流域における雲の日内特性
WATANABE YAMATO, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 58, 70, ROMBUNNO.B-02, 318, Feb. 2014
土木学会, Japanese

強風下に伴う混合気液界面の熱画像計測
TASHIRO KOKI, WATANABE YASUNORI, YAMADA TOMOHITO, OTSUKA JUN'ICHI, OYAMA TAKAHIRO, 土木学会北海道支部論文報告集(CD-ROM), 70, ROMBUNNO.B-65, Feb. 2014
Japanese

Clausius‐Clapeyron式に基づく日平均気温と降水強度の関係式を用いた将来における1時間降水強度の極値推定法
FUKUSHIMA TAIKI, YAMADA TOMOHITO, FARUKH MURAD AHMED, 土木学会北海道支部論文報告集(CD-ROM), 70, ROMBUNNO.B-01, Feb. 2014
Japanese

乱流‐氷界面に発達する界面波
NAITO KENSUKE, IZUMI NORIHIRO, YOKOKAWA MIWA, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 70, ROMBUNNO.B-37, Feb. 2014
Japanese

回転水槽における砂面に表面流がもたらす地形形成
ARIGA MASANOBU, YAMADA TOMOHITO, IZUMI NORIHIRO, YOKOKAWA MIWA, 土木学会北海道支部論文報告集(CD-ROM), 70, ROMBUNNO.B-39, Feb. 2014
Japanese

風洞水槽における有義波高の影響を考慮した鉛直風速分布に関する考察
OYAMA TAKAHIRO, YAMADA TOMOHITO, WATANABE YASUNORI, OTSUKA JUN'ICHI, 土木学会北海道支部論文報告集(CD-ROM), 70, ROMBUNNO.B-64, Feb. 2014
Japanese

2013年台風18号の降雨形態の特徴
NAKADAI GINGA, WATANABE YAMATO, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 70, ROMBUNNO.B-13, Feb. 2014
Japanese

重力風による氷床上でのステップ地形の形成に関する実験的研究
SUMIDA TAKASHI, NAITO KENSUKE, IZUMI NORIHIRO, YOKOKAWA MIWA, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 70号, 70, ROMBUNNO.B-38, Feb. 2014
Japanese

全球気候モデルと室内実験におけるブロッキング現象に関する考察
KITANO YOSHIKAZU, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 70, ROMBUNNO.B-11, Feb. 2014
Japanese

2010年のロシア熱波とパキスタン豪雨の発生メカニズムと因果関係の検討
TAKEUCHI DAIKI, FARUKH MURAD AHMED, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 70, ROMBUNNO.B-12, Feb. 2014
Japanese

Water Temperature Variation at the Mouth of Tanabe Bay during Typhoon Passing
馬場 康之, 水谷 英朗, 久保 輝広, 内山 雄介, 森 信人, 渡部 靖憲, 大塚 淳一, 山田 朋人, 猿渡 亜由未, 二宮 順一, 土木学会論文集B2(海岸工学), 70, 2, I_476, I_480, 2014
公益社団法人 土木学会, Japanese

Indian Monsoon Paths and Blocking Effects on Pakistan Extreme Rainfall Events
TAKEUCHI Daiki, YAMADA Tomohito J, Murad Ahmed Farukh, PROCEEDINGS OF ENVIRONMENTAL AND SANITARY ENGINEERING RESEARCH, 70, 5, I_263, I_269, 2014
Pakistan experienced an extreme rainfall event in July to August 2010. Two of the major contributing factors behind this extreme event were upper level stagnant blocking over western Russia and meandering pattern of Indian monsoon. In this study, monsoon patterns were identified. The kind of monsoon pattern that affected 2010 Pakistan flood consists of 64% of total flooding events in Pakistan. We focus on sea level pressure anomaly on 3 identified patterns of monsoon meandering. In 2010 Pakistan flooding case, the sea level pressure anomaly over the Middle East was lower, whereas, the anomaly over Northwestern Russia was higher. Moreover, 2010 Pakistan flooding case was affected by stagnant upper level (500hPa) blocking to descend cold air from Siberia to Pakistan. The number of monsoon meandering pattern which affects Pakistan flood tended to increase from June to August. On the other hand, the number of simultaneous occurrence of upper level blocking tended to decrease from June to August., Japan Society of Civil Engineers, Japanese

CATCHMENT STORAGE ESTIMATION BASED ON TOTAL RAINFALL-TOTAL LOSS RAINFALL RELATIONSHIP FOR 47 CATCHMENTS IN JAPAN
SUPRABA Intan, YAMADA Tomohito J, 水工学論文集 土木学会水工学委員会 編, 58, 4, 169, 174, 2014
One of the main objectives of research in hydrology is to improve the accuracy of catchment storage estimation for water resources management and flood prediction purposes. Rain water falling to the ground surface will either run off along the surface or infiltrate into the soil. The infiltrated water which is defined as loss rainfall can be used to estimate the potential catchment storage.
Total rainfall-total loss rainfall relationship has been developed to estimate catchment storage by using tanh function fitting curve for 47 catchments located in 16 prefectures in Japan between 2002 and 2011 (June to October). The obtained results indicate that runoff parameters in the tanh function represented by a and b parameters can be utilized to estimate the potential water storage for catchments having stabilized tanh curve type. Among 47 catchments, only 23.4% of the overall catchments have stabilized tanh curve types which are located in Honshu Island., 土木学会, English

北海道を対象とした地域気候予測研究について
SATO TOMONORI, YAMADA TOMOHITO, INATSU MASARU, NAKAMURA KAZUKI, SUGIMOTO SHIORI, MIYAZAKI MAKOTO, KUNO RYUSUKE, 日本農業気象学会全国大会講演要旨, 2014, 88, 2014
Japanese

Water Temperature Variation at the Mouth of Tanabe Bay during Typhoon Passing
BABA YASUYUKI, MIZUTANI HIDEAKI, KUBO TERUHIRO, UCHIYAMA YUSUKE, MORI NOBUHITO, WATANABE YASUNORI, OTSUKA JUN'ICHI, YAMADA TOMOHITO, SARUWATARI AYUMI, NINOMIYA JUN'ICHI, 土木学会論文集 B2(海岸工学)(Web), 70, 2, I.476-I.480 (J-STAGE), I_480, 2014
The intensive field observations have been carried out in the summer seasons since 2009 around the mouth of Tanabe bay, Wakayama prefecture. During the intensive observation in 2013, a typhoon18 (MAN-YI) approached close to Kii peninsula in the middle of September. It is found during the typhoon passing that coastal upwelling through the Ekman transport happened clearly due to continuous southward wind. As a result of time-frequency analysis, the water temperature variations have a dominant period longer than tidal period. An EOF analysis decomposes the water temperature variation during the typhoon passing into 1) the increase and decease of water temperature and 2) the magnitude of the temperature difference in the vertical direction., Japan Society of Civil Engineers, Japanese

高度な陸域要素モデルの開発とそれを用いた全球スケールの気候変動研究
ITO AKIHIKO, HANASAKI NAOTA, YOKOHATA TOKUTA, KATO ETSUSHI, YAMADA TOMOHITO, MASUTOMI YUJI, 国立環境研究所スーパーコンピュータ利用研究年報 平成25年度, 31, 37, 2014
Japanese

北海道を対象とした地域気候予測研究の動向
佐藤友徳, 山田朋人, 稲津將, 中村一樹, 杉本志織, 宮崎真, 久野龍介, 北海道の農業気象, 65, 12, 22, 31 Oct. 2013
Japanese

放射線防護のための人体における放射性同位体に起因する内部被曝による実効線量を計算する運動学的方法論
SASAKI SHOTA, YAMADA TADASHI, YAMADA TOMOHITO, 核医学, 50, 3, 220, 30 Sep. 2013
Japanese

Hydrological Characteristics of The 2011 Chao Phraya River Flood Disaster in Thailand
KOMORI DAISUKE, YAMADA TOMOHITO, 北海道地区自然災害科学資料センター報告, 26, 46, 51, 31 Mar. 2013
北海道大学大学院工学研究科北海道地区自然災害科学資料センター, Japanese

豪雨がもたらす大気境界層内の風速分布への影響
OYAMA TAKAHIRO, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 69, ROMBUNNO.B-02, Feb. 2013
Japanese

冬期札幌の降雨現象に関連する低気圧の軌跡とその大気特性
TAKAGI TAKUMA, TANAKA GAKU, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 69, ROMBUNNO.B-19, Feb. 2013
Japanese

北海道における農業活動を考慮した陸面過程モデルの構築
KONO TAKENORI, YAMADA TOMOHITO, POKHREL YADU, 土木学会北海道支部論文報告集(CD-ROM), 69, ROMBUNNO.B-21, Feb. 2013
Japanese

氷上に形成されるステップ地形
NAITO KENSUKE, IZUMI NORIHIRO, YOKOKAWA MIWA, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 69, ROMBUNNO.B-07, Feb. 2013
Japanese

山の風下側に発生する雲パターンの空間的分類
KITANO YOSHIKAZU, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 69, ROMBUNNO.B-01, Feb. 2013
Japanese

北半球中緯度におけるブロッキング現象の出現頻度と大規模気象場の物理特性
KAMADA DAISUKE, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 69, ROMBUNNO.B-06, Feb. 2013
Japanese

人間活動の影響を考慮した全球気候モデルの構築
YAMAHARA KOKI, YAMADA TOMOHITO, POKLREL YADU, 土木学会北海道支部論文報告集(CD-ROM), 69, ROMBUNNO.B-03, Feb. 2013
Japanese

石狩勇払地域の海陸風循環と道央近海の海面温度の年々変動特性
FUKUSHIMA TAIKI, YAMADA TOMOHITO, MIYAZAKI SHIN, 土木学会北海道支部論文報告集(CD-ROM), 69, ROMBUNNO.B-04, Feb. 2013
Japanese

豊平川上流域における陸面過程モデルに保水能分布を考慮した流出予測手法の開発
ISHIDA RYOHEI, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 69, ROMBUNNO.B-24, Feb. 2013
Japanese

MTSATの輝度温度情報による雲分類手法を用いたインドシナ半島周辺域における雲の気候特性
WATANABE YAMATO, YAMADA TOMOHITO, SUSENO DWI, PRABOWO YUGA, 土木学会北海道支部論文報告集(CD-ROM), 69, ROMBUNNO.B-05, Feb. 2013
Japanese

1990年から2010年の間に北海道で発生した線状降水帯の天気図型による分類と気象特性
SASAKI JUN, YAMADA TOMOHITO, MATSUOKA NAOKI, 土木学会北海道支部論文報告集(CD-ROM), 69, ROMBUNNO.B-20, Feb. 2013
Japanese

石狩川流域における泥炭土の地盤沈下量から推定した地下水位変化量
WACHI KOKI, YAMADA TOMOHITO, SUZUKI EIICHI, 土木学会北海道支部論文報告集(CD-ROM), 69, ROMBUNNO.B-23, Feb. 2013
Japanese

THE CLOUD CLIMATOLOGY OVER SOUTHEASTERN ASIAN REGIONS BY USING MTSAT CLOUD CLASSIFICATION
渡部 大和, 山田 朋人, Suseno Dwi Prabowo Yuga, 水工学論文集 土木学会水工学委員会 編, 57, 1_301, 306, 2013
土木学会, Japanese

FREQUENCY OF ATMOSPHERIC BLOCKING ASSOCIATED WITH MERIDIONAL SURFACE TEMPERATURE CHARACTERISTICS IN BOREAL WINTER IN THE MID-LATITUDES
YAMADA Tomohito J., HATA Yoshihiro, 水工学論文集 土木学会水工学委員会 編, 57, 1_397, 402, 2013
土木学会, English

SUB-SEASONAL HYDROLOGICAL FORECAST SKILLS IN A DROUGHT EVENT ASSOCIATED WITH LAND INITIALIZATIONS INCLUDING HUMAN ACTIVITIES IN AN ATMOSPHERIC GENERAL CIRCULATION MODEL
山原 康希, 山田 朋人, POKHREL Yadu, 水工学論文集 土木学会水工学委員会 編, 57, 1_1807, 1812, 2013
土木学会, Japanese

LAND AND SEA BREEZE ASSOCIATED TEMPERATURE GRADIENT BETWEEN ISHIKARI AREA AND YUHUTSU AREA
福島 大輝, 山田 朋人, 宮崎 真, 水工学論文集 土木学会水工学委員会 編, 57, 1_1759, 1764, 2013
土木学会, Japanese

Frequency of atmospheric blocking in the middle lattitude
Kamada Daisuke, Yamada Tomohito, Proceeding of Annual Conference, 26, 0, 192, 192, 2013
Atmospheric blocking is one of the main causes of extreme meteorological events such as spells of extremely cold weather, heat wave and continuous heavy rainfall in the mid-latitudes. Outputs of two General Circulation Models (MIROC and MPI GCMs) were analyzed to clarify the characteristics of the frequency of atmospheric blocking in December, January, and February for both for current climate and future climate conditions.The both GCM(MPI GCM and MIROC GCM) shows that ,in the future, frequency of the atmospheric blocking will increase,compared by the frequency of atmospheric blocking in the present climate., THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

AN EXPERIMENTAL STUDY OF STEP TOPOGRAPHY ON THE ICE SURFACE
YOKOKAWA MIWA, IZUMI NORIHIRO, NAITO KENSUKE, YAMADA TOMOHITO, GREVE RALF, 土木学会論文集 B1(水工学)(Web), 69, 4, I.1129-I.1134 (J-STAGE), I_1134, 2013
The spiral troughs observed on the surface of Mars' north polar ice cap show upstream-migrating structures, which indicate that those may possibly be cyclic steps formed by a density current created by cooling of the atmosphere due to the ice. It can be useful to estimate the formative process of the Mars' polar ice cap and thus the climatic history of Mars using the analogues of cyclic steps on the Earth. In this study, we have performed a series of physical experiments aimed at the formation of cyclic steps on ice by flowing fluid. Temperature distribution plays a quite important role for the formation and development of step topography on the ice surface, and was set as ice ‹ fluid ‹ ambient air in this experiment. As a result, step topography was formed on the ice except the case whose Fr is lowest, i.e., 0.76, and the steps generally developed upstream direction. The results of the present experiment agree with the mathematical model describing the evolution of the ice surface by flowing fluid., Japan Society of Civil Engineers, Japanese

北海道を対象とする総合的ダウンスケーリングの開発と適応
INATSU MASARU, YAMADA TOMOHITO, SATO TOMONORI, NAKAMURA KAZUKI, SUGIMOTO SHIORI, MIYAZAKI MAKOTO, KUNO RYUSUKE, 細氷(Web), 59, WEB ONLY, 2013
Japanese

FREQUENCY OF ATMOSPHERIC BLOCKING ASSOCIATED WITH MERIDIONAL SURFACE TEMPERATURE CHARACTERISTICS IN BOREAL WINTER IN THE MID-LATITUDES
YAMADA TOMOHITO, HATA YOSHIHIRO, 土木学会論文集 B1(水工学)(Web), 69, 4, I.397-I.402 (J-STAGE), 402, 2013
土木学会, English

全球気候モデルと室内実験におけるブロッキング現象に関する考察
KITANO YOSHIKAZU, YAMADA TOMOHITO, 細氷(Web), 59, WEB ONLY, 2013
Japanese

Clausius‐Clapeyron関係に基づく短時間極端降水強度推定法
FUKUSHIMA TAIKI, YAMADA TOMOHITO, 細氷(Web), 59, WEB ONLY, 2013
Japanese

MTSATによる近赤外放射情報を基にした雲分類手法を用いた雨季のチャオプラヤ川流域における雲の出現特性
WATANABE YAMATO, YAMADA TOMOHITO, 細氷(Web), 59, WEB ONLY, 2013
Japanese

全球気候モデルMIROCへの新規陸域モデルの結合とその大気陸域相互作用研究への応用
HANASAKI NAOTA, ITO AKIHIKO, YAMADA TOMOHITO, KANAE SHINJIRO, OKI TAIKAN, 国立環境研究所スーパーコンピュータ利用研究年報 平成24年度, 35, 40, 2013
Japanese

Field Measurements at Tanabe-Nakashima Observation Tower in the Summer of 2013
BABA YASUYUKI, MIZUTANI HIDEAKI, KUBO TERUHIRO, UCHIYAMA YUSUKE, MORI NOBUHITO, WATANABE YASUNORI, YAMADA TOMOHITO, SARUWATARI AYUMI, OTSUKA JUN'ICHI, 京都大学防災研究所年報(CD-ROM), 57, 455, 461, 2013
This paper shows some results of a field observation carried out in the summer of 2013. The vertical profiles of currents and water temperature have been measured as well as wave and wind conditions, and salinity and dissolved oxygen level observations have been carried out at the observation tower of Shirahama Oceanographic Observatory. During the observation, one typhoon (No.18, MAN-YI) approached to the Kii peninsula. When the typhoon passed around the observation site, the vertical mixing develops well, and water temperature at all measurement points show almost uniform distributions. It is also found during the typhoon passing that coastal upwelling through the Ekman transport happened clearly due to continuous southward wind. An EOF analysis decomposes the water temperature variation during the typhoon passing into 1) the increase and decease of water temperature and 2) the magnitude of the temperature difference in the vertical direction., 京都大学防災研究所, Japanese

海陸の熱的コントラストの変化に伴う石狩川流域における水循環システムの解明—Hydrological Cycles over Ishikari River Basin associated with Change of Land-Sea Thermal Contrast
山田 朋人, 福島 大輝, 宮崎 真, 泉 典洋, 研究所紀要 / [北海道河川財団] [編], 23, 139, 145, Dec. 2012
北海道河川財団, Japanese

Model estimates of sea-level change due to anthropogenic impacts on terrestrial water storage
Yadu N. Pokhrel, Naota Hanasaki, Pat J-F. Yeh, Tomohito J. Yamada, Shinjiro Kanae, Taikan Oki, NATURE GEOSCIENCE, 5, 6, 389, 392, Jun. 2012
Global sea level has been rising over the past half century, according to tide-gauge data(1,2). Thermal expansion of oceans, melting of glaciers and loss of the ice masses in Greenland and Antarctica are commonly considered as the largest contributors, but these contributions do not entirely explain the observed sea-level rise(1). Changes in terrestrial water storage are also likely to affect sea level(3-6), but comprehensive and reliable estimates of this contribution, particularly through human water use, are scarce(1). Here, we estimate sea-level change in response to human impacts on terrestrial water storage by using an integrated model that simulates global terrestrial water stocks and flows (exclusive to Greenland and Antarctica) and especially accounts for human activities such as reservoir operation and irrigation. We find that, together, unsustainable groundwater use, artificial reservoir water impoundment, climate-driven changes in terrestrial water storage and the loss of water from closed basins have contributed a sea-level rise of about 0:77 mm yr(-1) between 1961 and 2003, about 42% of the observed sea-level rise. We note that, of these components, the unsustainable use of groundwater represents the largest contribution., NATURE PUBLISHING GROUP, English

夏季における石狩~苫小牧間の海陸風循環
FUKUSHIMA TAIKI, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-05, Feb. 2012
Japanese

全球大気大循環モデルにおける人間活動の影響による陸面初期値を用いた極端現象の準季節水文予報スキル
YAMAHARA KOKI, YAMADA TOMOHITO, POKHREL YADU, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-28, Feb. 2012
Japanese

人工衛星の近赤外放射データを使用した雲分類手法による東南アジアにおける極端現象の物理的特徴の解明
WATANABE YAMATO, SUSENO DWI, PRABOWO YUGA, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-16, Feb. 2012
Japanese

陸面過程モデルMATSIROと保水能理論および集中定数系方程式の統合手法開発
NAKAYAMA YUTA, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-24, Feb. 2012
Japanese

1990年から2010年に発生した北海道における線状降水帯の統計的性質と大規模場の影響に見られる特徴
SASAKI JUN, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-08, Feb. 2012
Japanese

南北温度勾配の減少による大気卓越波の増幅とブロッキングの形成
HATA YOSHIHIRO, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-13, Feb. 2012
Japanese

密度界面に発生するship waveの物理機構
KITANO YOSHIKAZU, YAMADA TOMOHITO, IZUMI NORIHIRO, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-11, Feb. 2012
Japanese

2011年7月新潟・福島豪雨において発生した線状降水帯の形状特性・環境場に関する考察
WADA TAKUYA, YAMADA TOMOHITO, SUSENO DWI, PRABOWO YUGA, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-09, Feb. 2012
Japanese

北海道における人間活動を考慮した水循環モデルの検討
KONO TAKENORI, YAMADA TOMOHITO, POKHREL YADU, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-27, Feb. 2012
Japanese

火星北極冠におけるサイクリックステップに関する実験的研究
NAITO KENSUKE, SHIMIZU HIROKI, IZUMI NORIHIRO, YOKOKAWA MIWA, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-56, Feb. 2012
Japanese

降水粒子の粒径分布特性
AKUTSU HIROSHI, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-12, Feb. 2012
Japanese

寒冷地における厳冬期の気温変動と降雨現象の特性
YAHATA YOSEI, TANAKA GAKU, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 68, ROMBUNNO.B-14, Feb. 2012
Japanese

The Inverse Estimation Of Parameter On Runoff Analysis and Runoff Characteristic
Yoshimi Kazuhiro, Yamagami Kunihiro, Okabe Masato, Yamada Tadashi, Proceeding of Annual Conference, 25, 224, 2012
A lot of rainfall-runoff models are proposed conventionally. However, there is always uncertainty of the parameters of those models because we estimate them by using the past hydrological data. Therefore, it is difficult to decide parameters. In this thesis, we estimate the parameters of the lumping model for runoff analysis in a slope from the past hydrological data . In addition, we propose a barometer to decide the effective rainfall easily in the various rainfall by showing the relationship between total amount of rainfall and total amount of effective rainfall expressed by the parameters that we estimated., THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

Two-dimensional, threshold-based cloud type classification using MTSAT data
Dwi Prabowo Yuga Suseno, Tomohito J. Yamada, REMOTE SENSING LETTERS, 3, 8, 737, 746, 2012
A new two-dimensional threshold diagram (2D-THR) has been developed based on maximum likelihood cloud classification results, which can readily be applied for Multi-functional Transport Satellite (MTSAT) split window datasets. Because 2D-THR was trained using northern summer 2010 data for Japan and its surrounding area, it is typically suitable only for summer. Comparison of snapshot cloud type distributions showed that 2D-THR images and the corresponding night-time microphysical colour composite images as well as 2D-THR images and Japan Meteorological Agency (JMA) cloud type images are in good agreement. A time series inter-comparison of the hourly 2D-THR cloud classification results with the JMA cloud type classification data product was performed by calculating spatial correlation of cloud percentage for 1 degrees x 1 degrees grid cells. For cumulonimbus, high-level, middle-level and low-level clouds over tropical and subtropical areas in the northwestern Pacific Ocean region, the spatial correlation between 2D-THR and JMA is moderate. Thus, 2D-THR cloud classification algorithm can be applied in both regions., TAYLOR & FRANCIS LTD, English

The Development range of disturbance on the atmospheric density stratification
Kitano Yoshikazu, Yamada Tomohito, Izumi Norihiro, Proceeding of Annual Conference, 25, 0, 142, 142, 2012
There are many unknown issues about line-shaped rainbands (LRBs) which is one of the meso-scale meteorological phenomena making torrential rainfall events in Japan. The LRBs caused severe floods and landslide disasters such as the Fukui heavy rainfall in 2004 and the Hokkaido heavy rainfall in 2010. For disaster prevention, it is important to reveal the formation mechanism of LRBs. In Order to know the mechanism, the authors try to examine the stability of the density stratification using the method of stationary phase. To simplify the discussion, this theory considers only the up/down motion of the disturbance in the stratified atmosphere., THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

Long-term changes of meteorological elements on the coldest period in snowy cold region
TANAKA GAKU, Yahata Yosei, Yamada Tomohito, Proceeding of Annual Conference, 25, 0, 248, 248, 2012
The coldest period of winter is one of the twenty-four divisions of the four seasons and is around January 20 in solar calendar.  However, the temperature on the coldest period recently rises and the snow changed often to rain.    In this paper, we examine long-term changes of meteorological elements on the coldest period in snowy cold region.  And it could be confirmed that the temperature and the frequency of rainfall, observed in Sapporo in Japan are changing cyclically with about 20 to 25 years., THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

全球気候モデルMIROCへの新規陸域モデルの結合とその大気陸域相互作用研究への応用
HANASAKI NAOTA, ITO AKIHIKO, YAMADA TOMOHITO, KANAE SHINJIRO, OKI TAIKAN, POKHREL YADU NATH, 国立環境研究所スーパーコンピュータ利用研究年報 平成23年度, 43, 48, 2012
Japanese

北海道岩尾内ダム流域における融雪出水量予測精度と水文特性の経年変化特性
YAMADA TOMOHITO, WACHI KOKI, 地球環境研究論文集, 19, I.41-I.46, 46, 15 Sep. 2011
土木学会, Japanese

保水能効果を有する降雨流出予測手法の高精度化に向けた陸面モデルの活用
YAMADA TOMOHITO, KURE SHUICHI, 地球環境研究論文集, 19, I.91-I.96, 96, 15 Sep. 2011
土木学会, Japanese

GEOSTATIONARY SATELLITE BASED RAINFALL ESTIMATION AND VALIDATION AND ITS FUTURE DEVELOPMENT
SUSENO, YUGA DWI PRABOWO, YAMADA TOMOHITO J, 土木学会北海道支部論文報告集(CD-ROM), 67, ROMBUNNO.B-47, Feb. 2011
English

降雨流出計算手法の精度向上に向けた陸面モデル情報の利用
YAMADA TOMOHITO, KURE SHUICHI, 土木学会北海道支部論文報告集(CD-ROM), 67, ROMBUNNO.B-38, Feb. 2011
Japanese

近年発生した線状降水帯の形状に関する事例研究
WADA TAKUYA, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 67, ROMBUNNO.B-43, Feb. 2011
Japanese

全球気候モデルにおける極端現象と大気陸面相互作用の関係
YAMAHARA KOKI, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 67, ROMBUNNO.B-50, Feb. 2011
Japanese

光学式降雨検知システムを用いた降水粒子の粒径分布特性に関する検討
AKUTSU HIROSHI, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 67, ROMBUNNO.B-49, Feb. 2011
Japanese

北海道における近年の線状降水帯特性
SASAKI JUN, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 67, ROMBUNNO.B-44, Feb. 2011
Japanese

石狩川流域における河川水位と地下水位の関係に関する事例報告
WACHI KOKI, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 67, ROMBUNNO.B-24, Feb. 2011
Japanese

気候変動に伴う南北温度勾配と大気波数の変化による極端現象増加メカニズム
HATA YOSHIHIRO, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 67, ROMBUNNO.B-46, Feb. 2011
Japanese

EFFECT OF NONLINEARITY PARAMETERS IN THE RUNOFF ANALYSIS ON RUNOFF PHENOMENON
Yoshimi Kazuhiro, Watanabe Akihito, Okabe Masato, Yamada Tadashi, Proceeding of Annual Conference, 24, 115, 115, 2011
THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

Effect Of Runoff Suppressant By Rainfall Harvesting On The Top Of The Building
Isogai Jiro, Yoshimi Kazuhiro, Okabe Masato, Misaka Ikusei, Inaba Kaoru, Maenami Hiroki, Konoshima Takehiko, Yamada Tadashi, Proceeding of Annual Conference, 24, 126, 126, 2011
THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

Effect Of Heat Environment Mitigation By Rainfall Harvesting On The Top Of The Building
Okabe Masato, Isogai Jiro, Yoshimi Kazuhiro, Misaka Ikusei, Inaba Kaoru, Maenami Hiroki, Yamada Tadashi, Proceeding of Annual Conference, 24, 127, 127, 2011
THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

保水能効果を有する降雨流出予測手法の高精度化に向けた陸面モデルの活用　　　　　　　　　　　　　　　
山田朋人, 呉修一, 土木学会地球論文集Ｇ(環境), 67, 5, I_91-I_96, 2011

Statistical Characteristics of Line-Shaped Rain Bands over Hokkaido in Recent Years
sasaki jun, yamada tomohito, Proceeding of Annual Conference, 24, 0, 151, 151, 2011
水文・水資源学会, Japanese

Subseasonal Forecast of Heavy Rainfall Ivent by use of Land Information in a General Circulation Model
yamahara kouki, yamada tomohito, Proceeding of Annual Conference, 24, 0, 152, 152, 2011
水文・水資源学会, Japanese

Large Scale Characteristics of Line Shaped Rainbands over Hokkaido Region
Yamada Tomohito, Sasaki Jun, Proceeding of Annual Conference, 24, 0, 49, 49, 2011
水文・水資源学会, Japanese

The relationship between land subsidence and fluctuation of groundwater level
WACHI Kouki, YAMADA Tomohito, SUZUKI Eiichi, Proceeding of Annual Conference, 24, 0, 92, 92, 2011
石狩川において治水事業が行われてから2010年で100年を迎えた．石狩川の改修は河川蛇行部を直線化し、流れを円滑にする捷水路工事が主体となって進められた．これは，洪水を短時間で排水すること並びに，地下水位を下げ，湿地を農地や住宅地に利用可能にすること目標とした．しかし，現在と明治31年頃の地下水位変化を調べるためには過去の水位データが乏しく，直接経年変化を調査するのは厳しい．そのため，河川水位，地盤高，地形地質等の限られたデータからアプローチすることが必要である．また，上記の通り2010年は石狩川治水100年の記念の年であることから，地下水についても同様に注目されている．本研究では，泥炭層における地盤沈下量を算出し，それによる排水量から地下水位変化量を測定し，明治39年当時の地下水位を90cm低下させるという目標をどれだけ達成できたのか評価することを研究目的とする．, 水文・水資源学会, Japanese

Interfacial Process of Ocean under Rainfall
WATANABE Yasunori, TADAKI Shinji, YAMADA Tomohito, PROCEEDINGS OF THE JAPANESE CONFERENCE ON COASTAL ENGINEERING, 67, 2, 61, 65, 2011
Deformations of air-water interfaces throughout a splash event of falling water drops on a still water surface were studied in this paper on the basis of back-light imaging measurements.A series of interfacial processes, formations of fine sprays shedding from crown tips, air bubbles released from the center of a cavity, secondary droplets fragmented from a centric jet, was parameterized with Froude and Weber numbers as well as relative densities of impacting and receiving liquids with the aim to develop a future model to describe local heat and moisture exchanges between atmosphere and ocean under rainfall., Japan Society of Civil Engineers, Japanese

Characterizing storm severity by using geostationary satellite rainfall
Suseno Dwi, Prabowo Yuga, Yamada Tomohito J, Proceeding of Annual Conference, 24, 0, 17, 17, 2011
Thunderstorm or extreme rainfall causing flash flood characteristics are very important to understand and to characterize storms related to such flash flood. Those of characteristics include storm geometry, movement, speed, orientation, direction, recurrent interval, Intensity-Duration-Frequency (IDF) and regional frequency. Those analyses mainly have conducted by using observed rainfall acquired from dense rain gauge network or rainfall radar data. This research aims to characterizing storm severity of extreme rainfall caused flash flood. Considering a remote area or ungauge basin that lack of rainfall measurement, we use the geostationary satellite rainfall estimation to characterize those of storm severity., 水文・水資源学会, Japanese

GEOSTATIONARY SATELLITE BASED RAINFALL ESTIMATION AND VALIDATION: A CASE STUDY OF JAVA ISLAND, INDONESIA
SUSENO Dwi, Prabowo Yuga, YAMADA Tomohito J, PROCEEDINGS OF THE JAPANESE CONFERENCE ON HYDRAULICS, 67, 4, I_43, I_48, 2011
Near real time rainfall information is necessary for early warning of rainfall triggered hazard such as floods and landslides. Remote sensing based rainfall estimation has been considered to be used to fulfill that purpose. This research is addressed to use geostationary based rainfall estimation by using Multi Transport Satellite (MTSAT) data which is blended with Tropical Rainfall Measuring Mission (TRMM) 2A12 datasets in order to provide near real time rainfall information, especially for hazard study purposes over Java Island, Indonesia. Comparison to TRMM Multi Precipitation Analysis (TMPA) datasets is performed. Spatial and temporal validation of those rainfall estimations is conducted by validating them with available rain gauge data during a rainy season in December 2007. Temporal validation result shows that TMPA demonstrated better statistical performance than MTSAT blended. However for the spatial correlation, MTSAT blended shows relatively better performance than TMPA., Japan Society of Civil Engineers

大気陸面相互作用に着目した水文気象諸量の予測可能性と北海道における豪雨特性
YAMADA TOMOHITO, 気象講座「新しい気象」テキスト, 29th, 24, 27, 2011
Japanese

北海道における近年の線状降水帯と豪雨特性
YAMADA TOMOHITO, SASAKI JUN, 環境科学会年会プログラム, 2011, 190, 191, 2011
Japanese

全球気候モデルMIROCへの新規陸域モデルの結合とその大気陸域相互作用研究への応用
HANASAKI NAOTA, ITO AKIHIKO, YAMADA TOMOHITO, KANAE SHINJIRO, OKI TAIKAN, 国立環境研究所スーパーコンピュータ利用研究年報 平成22年度, 41, 47, 2011
Japanese

火星の北極冠に見られるスパイラルトラフの形成過程についての実験的研究:予報
SHIMIZU HIROKI, YOKOKAWA MIWA, NAITO KENSUKE, IZUMI NORIHIRO, YAMADA TOMOHITO, GREVE RALF, SHIRAIWA TAKAYUKI, 日本堆積学会大会プログラム・講演要旨, 2011, 63, 2011
Japanese

Interfacial Process of Ocean under Rainfall
WATANABE YASUNORI, TADAKI SHINJI, YAMADA TOMOHITO, 土木学会論文集 B2(海岸工学), 67, 2, 61, 65, 2011
土木学会, Japanese

Land-Atmosphere Interactions and Hydro-Meteorological Forecasting Associated with Land Surface States
Koster Randal D, Proceedings, ... meeting of Japan Society of Fluid Mechanics, 2010, 0, 85, 85, 09 Sep. 2010
Knowledge of subsurface soil moisture contributions at the start of seasonal or subseasonal forecasts can potentially increase the skill of hydrometeorological forecast through the impact of soil moisture on the surface energy budget and associated evolution of meteorological quantities. This presentation introduces the contribution of soil moisture initializations to subseasonal hydrological forecast skills at one of the most severe drought events in 20th century (The drought of 1988 in US). Soil moisture initializations are based on offline land surface model simulations with realistic at..., Japan Society of Fluid Mechanics, Japanese

東京における120年分時間降雨量データを用いた降雨形態の変化に関する研究
WADA TAKUYA, YAMADA TOMOHITO, 地球環境シンポジウム講演集, 18th, 13, 18, 27 Aug. 2010
土木学会, Japanese

天塩川流域岩尾内ダムにおける融雪出水量と積雪水量の関係
WACHI MITSUTAKA, YAMADA TOMOHITO, 土木学会年次学術講演会講演概要集(CD-ROM), 65th, 0, ROMBUNNO.II-255, 31, 05 Aug. 2010
Accurate prediction for snow melting amount is important for water resources in heavy snow regions. However, the quantity of snow melt runoff was estimated less than snow water equivalent after 2008 in Iwaonai dam reservoir, Teshio river basin. The predicted snow melt runoff was smaller than the observed snow melt runoff both in 2008 (66%) and 2009(74%).Focused on these years, the timing of snow melt runoff to the dam lake reservoir tends to be earlier than the 38-year average (climatology), and the daily temperature in mid-March through mid-May also tends to be higher than the climatology. Our results show that about 35% of the underestimation is caused by the snow-evaporation and the snow-melting runoff due to rainfall in 2008 and 47% of the underestimation is caused in 2009., THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

陸面モデルを用いた融雪期間中の土壌水分,凍結土壌水分の融雪出水に対する影響評価
NAKAYAMA YUTA, YAMADA TOMOHITO, 土木学会年次学術講演会講演概要集(CD-ROM), 65th, ROMBUNNO.II-316, 05 Aug. 2010
Japanese

東京における継続時間,Peak雨量から見たひと雨形態の考察
WADA TAKUYA, YAMADA TOMOHITO, 土木学会年次学術講演会講演概要集(CD-ROM), 65th, ROMBUNNO.II-282, 05 Aug. 2010
Japanese

大気陸面相互作用と陸面情報を用いた水文気象予測研究
YAMADA TOMOHITO, 衛生工学シンポジウム論文集, 18th, 33, 01 Jul. 2010
Japanese

塩水表面の凍結に伴う鉛直対流と氷層下の形状パターン
TSUJI HIKARU, YAMADA TOMOHITO, IZUMI NORIHIRO, 土木学会北海道支部論文報告集(CD-ROM), 66, ROMBUNNO.B-51, Feb. 2010
Japanese

東京における長期間データを用いた降雨の日変化形の経年変化
WADA TAKUYA, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 66, ROMBUNNO.B-37, Feb. 2010
Japanese

大気陸面相互作用と土壌水分特性を利用した極端現象の準季節予報スキル
YAMADA TOMOHITO, KOSTER RANDAL D, KANAE SHINJIRO, OKI TAIKAN, 土木学会北海道支部論文報告集(CD-ROM), 66, ROMBUNNO.B-34, Feb. 2010
Japanese

地球温暖化に伴う気候変動が大気循環の波数に与える影響
HATA YOSHIHIRO, YAMADA TOMOHITO, IZUMI NORIHIRO, 土木学会北海道支部論文報告集(CD-ROM), 66, ROMBUNNO.B-33, Feb. 2010
Japanese

天塩川流域岩尾内ダムにおける融雪出水量と積雪水量の係関係
WACHI KOKI, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 66, ROMBUNNO.B-29, Feb. 2010
Japanese

陸面モデルを用いた積雪量,土壌水分,凍結土壌水分の再現性
NAKAYAMA YUTA, YAMADA TOMOHITO, 土木学会北海道支部論文報告集(CD-ROM), 66, ROMBUNNO.B-31, Feb. 2010
Japanese

Validation of frozen soil moisture in a land surface model
NAKAYAMA YUTA, YAMADA TOMOHITO, Proceeding of Annual Conference, 23, 0, 38, 38, 2010
THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

The Relationship between Extreme Weather Events and Meridional Gradient of Temperature, Atmospheric Wave Numbers in Climate Change
Hata Yoshihiro, Yamada Tomohito, Proceeding of Annual Conference, 23, 0, 48, 48, 2010
THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

陸面情報を用いた準季節スケールの水文気象予報スキル
YAMADA TOMOHITO, KOSTER RANDAL D, KANAE SHINJIRO, OKI TAIKAN, 日本農業気象学会全国大会講演要旨, 2010, 156, 2010
Japanese

全球気候モデルMIROCの陸域過程の精緻化及びそれを用いた大気陸面相互作用の研究
HANASAKI NAOTA, ITO AKIHIKO, OKI TAIKAN, KANAE SHINJIRO, YAMADA TOMOHITO, YAMAZAKI DAI, SUZUKI AKIRA, CHO JAEIL, KIM HYUNGJUN, POKHREL YADU, 国立環境研究所スーパーコンピュータ利用研究年報 平成21年度, 27, 32, 2010
Japanese

Diurnal Characteristics of Summertime Rainfall over North America in a Dynamically Downscaled Reanalysis Dataset (US10)
YAMADA TOMOHITO J, LEE MYONG-IN, KANAMARU HIDEKI, KANAMITSU MASAO, 日本気象学会大会講演予稿集, 96, 96, 414, 414, 31 Oct. 2009
日本気象学会, English

P182 Diurnal Characteristics of Summertime Rainfall over North America in a Dynamically Downscaled Reanalysis Dataset (US10)
Yamada Tomohito J, Lee Myong-In, Kanamaru Hideki, Kanamitsu Masao, 大会講演予講集, 96, 414, 414, 31 Oct. 2009
社団法人日本気象学会, English

全球気候モデルMIROCの陸域過程の精緻化及びそれを用いた大気陸面相互作用の研究
HANASAKI NAOTA, ITO AKIHIKO, OKI TAIKAN, KANAE SHINJIRO, YAMADA TOMOHITO, YAMAZAKI DAI, SUZUKI SATOSHI, CHO JAEIL, KIM HYUNGJUN, 国立環境研究所スーパーコンピュータ利用研究年報 平成20年度, 25, 32, 2009
Japanese

全球気候モデルMIROCの陸域過程の精緻化及びそれを用いた大気陸面相互作用の研究
HANASAKI NAOTA, ITO AKIHIKO, OKI TAIKAN, KANAE SHINJIRO, YAMADA TOMOHITO, UTSUMI NOBUYUKI, YAMAZAKI DAI, 国立環境研究所スーパーコンピュータ利用研究年報 平成19年度, 27, 32, 2008
Japanese

Seasonality of land surface impact on precipitation variability
YAMADA TOMOHITO, KANAE SHINJIRO, OKI TAIKAN, PROCEEDINGS OF HYDRAULIC ENGINEERING, 50, 541, 546, 2006, [Peer-reviewed]
Japan Society of Civil Engineers, Japanese

ケンブリッジ大学における第14回地球環境流体力学サマｰスクｰルに参加して
山田 朋人, 土木学会誌, 90, 5, 58, 61, 15 May 2005
土木学会, Japanese

Locality of land surface impact on precipitation variability in boreal summer
Yamada Tomohito, Kanae Shinjiro, Oki Taikan, Proceeding of Annual Conference, 18, 0, 71, 71, 2005
THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES

“現実的”な陸面水文量の導入による夏の降水量の年々変動(1951‐98)のAGCMによる再現性
KANAE SHINJIRO, HIRABAYASHI YUKIKO, YAMADA TOMOHITO, OKI TAIKAN, 日本気象学会大会講演予稿集, 86, 86, 95, 95, Oct. 2004
日本気象学会, Japanese

Influence of atmosphere initial conditions for precipitation predictability in an Atmospheric General Circulation Model
Yamada Tomohito, Kanae Shinjiro, Oki Taikan, Proceeding of Annual Conference, 17, 0, 112, 113, 2004
THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES

地球温暖化に伴うアジアにおける降水量の年々変動の変化
YAMADA TOMOHITO, KANAE SHINJIRO, OKI TAIKAN, MUSHIAKE KATSUMI, 水工学論文集, 47, 97, 102, 10 Feb. 2003
To evaluate the effect of the global warming on precipitation is essential for future global water resourcemanagement. Previous studies have indicated the precipitation increase in Asian monsoon region. Fewprevious studies; however, have mentioned the interannual variability as the coefficient variation of precipitation (CVP) in sub continental scale. This paper has analyzed the dataset of the global warmingexperiments by general circulation models (GCMs) in JJA summer. The result has confirmed the increasein precipitation and the standard deviation of precipitation in East Asia region but revealed no increasein the interannual precipitation variability as CVP., Japan Society of Civil Engineers, Japanese

地球温暖化に伴う降水量変化パターンの統計解析
山田 朋人, 鼎 信次郎, 沖 大幹, 水文・水資源学会研究発表会要旨集, 16, 0, 54, 55, 2003
THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES, Japanese

水文・水資源学会誌 Vol.35, No.2　　　　　　　　　　　　　　　
山田朋人, 私にとっての発想のたまご
水文・水資源学会, Mar. 2022

ながれ　　　　　　　　　　　　　　　
一般社団法人日本流体力学会, 気候変動を踏まえた豪雨・洪水氾濫リスクの考え方
2021

総合土木技術誌土木施工　　　　　　　　　　　　　　　
オフィス・スペース, 気候変動下における大雨の将来リスクに関する新しい解釈と提案
2021

雑誌「河川」　　　　　　　　　　　　　　　
日本河川協会, アンサンブル手法による気候変動予測・リスク評価の考え方
2020

気候変動適応技術の社会実装ガイドブック　　　　　　　　　　　　　　　
SI-CATガイドブック編集委員会
技報堂出版, 2020, [Contributor]

国土交通省北海道開発局，北海道，北海道大学 監修：気候変動を踏まえた新しい洪水リスク解析　　　　　　　　　　　　　　　
一般財団法人 北海道河川財団
2019, [Supervisor]

水循環 Journal of hydrological system :貯留と浸透　　　　　　　　　　　　　　　
雨水貯留浸透技術協会, 気候変動下における積雪寒冷地域で想定される水循環，水資源の特徴
2019

水理公式集 [2018年度版]　　　　　　　　　　　　　　　
土木学会 水工学委員会, 第2章 気象と大気・陸面水文過程
2019, [Contributor]

生活と環境　　　　　　　　　　　　　　　
日本環境衛生センター, 将来の短時間豪雨の推定と降雨の不確実性―北海道を対象とする総合的ダウンスケール手法の開発と適用
2015

Designing Climate Change Adaptation　　　　　　　　　　　　　　　
三村 信男, 太田 俊二, 武若 聡, 亀井 雅敏
株式会社クロスメディア・マーケティング, 2015, [Contributor]

Resilience of bridge networks considering the escalation of natural disasters due to global warming
Grants-in-Aid for Scientific Research
01 Apr. 2023 - 31 Mar. 2028
秋山 充良, 山田 朋人, 本田 利器, 松崎 裕, 石橋 寛樹, 高橋 良和
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Waseda University, 23H00217

Climate change impact assessment for flood and drought y evaluating damage risks through repeated extreme events
Grants-in-Aid for Scientific Research
01 Apr. 2022 - 31 Mar. 2025
山田 朋人, 中津川 誠, 星野 剛
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 22H01594

令和元年台風19号及び台風21号による広域災害に関する総合研究
科学研究費助成事業
04 Dec. 2019 - 31 Mar. 2023
二瓶 泰雄, 中北 英一, 竹見 哲也, 山田 朋人, 三隅 良平, 飯塚 聡, 鈴木 真一, 仲江川 敏之, 柳瀬 亘, 立川 康人, 田中 茂信, 佐山 敬洋, 田中 智大, 朝位 孝二, 前野 詩朗, 田中 仁, 吉谷 純一, 田中 規夫, 泉 典洋, 矢野 真一郎, 森脇 亮, 赤松 良久, 内田 龍彦, 重枝 未玲, 岩崎 理樹, 清水 義彦, 小山 毅, 長谷川 兼一, 西嶋 一欽, 藤本 郷史, 毛利 栄征, 前田 健一, 岡村 未対, 卜部 厚志, 森口 周二, 蝦名 裕一, 松四 雄騎, 王 功輝, 竹林 洋史, 鈴木 素之, 田島 芳満, 佐々木 淳, 信岡 尚道, 森 信人, 有川 太郎, 鈴木 崇之, 下園 武範, 松井 正宏, 小林 文明, 畑山 満則, 牛山 素行, 佐藤 健, 梶谷 義雄
令和元年東日本台風（台風19号）とその2週間後の大雨（台風21号と低気圧）による広域災害の被害状況・メカニズムの全容を明らかにすることを目的とし，多角的・総合的に多くの分野の専門家からなる研究グループを結成し，調査研究を継続して行った．ここでは，①台風・低気圧による豪雨・流出現象の気象学的解明，②広域にわたる洪水氾濫災害を引き起こしたメカニズムの解明，③多発した土砂災害・土構造物破壊におけるメカニズムの解明，④強風や高潮による被害実態の解明，⑤住民の避難行動の実態と防災情報の伝達状況の把握，の5つのテーマと主に対象とした．その結果，台風19号による豪雨に，山岳部は勿論，平野部でもseeder-feeder機構が貢献していることを，XRAINによる立体観測情報，ひまわりによる観測情報により，seeder-feeder機構を表現した数値モデルを用いて示した．2019年台風19号による豪雨発生機構について，気象庁メソ客観解析データを用いて，降水活動に係る大気安定度や水蒸気場の解析をし，本豪雨発生時には，最近の他の豪雨事例と比較して，湿潤絶対不安定が持続して形成されていたことが分かった．また，洪水氾濫による建築被害に関しては，長野市内の水害被害住宅を対象に，復旧後の室内環境に着目して現地調査を実施している．復旧には数ヶ月の期間を要するが，復旧手順は現地の判断で実施している場合が多く，客観的な情報が整備されていない．その一助となるべく，限られた事例ではあるが，復旧手順とともにそれに伴う環境改善効果を評価しながら知見を蓄積し，環境改善を測るために室内の浮遊真菌濃度や部位の含水率等を計測した．さらに，風水害に関しては，台風に伴って発生した竜巻の影響が大きかったため，台風と竜巻発生の関係を過去の気象資料から抽出し整理した．
日本学術振興会, 特別研究促進費, 東京理科大学, 19K24678

Proposition of agricultural adaptation strategies by high-resolution climate change projection and crop dataset augmentation
Grants-in-Aid for Scientific Research
01 Apr. 2019 - 31 Mar. 2023
廣田 知良, 稲津 將, 山田 朋人, 西尾 善太, 小南 靖弘, 下田 星児, 村上 貴一, 臼井 靖浩, 横山 岳, 濱嵜 孝弘
大規模アンサンブル気象データベースd4pdfを用いて北海道のバレイショへの温暖化への影響と適応策の検討し、温暖化によって収量が低下するリスクは増加し、また作期の早期化では対応できず、高温耐性を持つ品種への転換が重要な適応策になることが明らかとなった。北海道の十勝川水系などの解析から大規模アンサンブル気象データベースd4pdfを用いて洪水リスクの定量化が実現した。北海道胆振東部地震が農地侵食に与える影響について、震災後は大規模土砂崩壊リスクが高まっていると推定され、将来における極端降雨における侵食リスクと共に考慮すべきであることを示した。北海道における冬季の気候変動が農業に与える影響については、１）小麦における雪踏みによる野良イモ防除について現地実証で有効性を示し、２）地形情報および高層気象の情報を説明変数として取り入れた機械学習により、冬季の厳寒条件における気温の空間補間値を補正する手法を開発すると共に、３）融雪水の浸透効果を取り組んだモデル化と４）大規模アンサンブル気象データベースd4pdfを土壌凍結深推定手法と組み合わせて解析する手法開発に着手、５）北海道の小麦栽培における融雪促進影響を検討し、融雪材の促進効果は地域や融雪材散布後の気象条件で与える効果が異なることがわかった。データレスキューでは北海道や関東の小麦、北海道における圃場作業記録、北海道のワイン用ブドウ、九州の1958年～2019年の過去60年の気象概況と農作概況および農業気象災害のデータレスキューについて、これまで入手困難あるいは注目されてこなかったデータも含めて収集が進んだ。また、行政ルートからのデータ収集探査を詳細に集める手法を検討すると共に、テンサイについては、昭和30年代に国の農業研究機関を中心に進められた暖地テンサイに関する各種資料が温暖化研究に展開できる可能性を見出した。
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), 19H00963

Evaluation method for water related disaster risk considering uncertainty of rainfall patterns, rainfall-runoff and flooding
Grants-in-Aid for Scientific Research
01 Apr. 2019 - 31 Mar. 2022
Yamada Tomohito
1)Based on a large amount of rainfall data, we classified the causes of extreme rainfall into thermodynamic and dynamic aspects, and it was also found that the increase in future rainfall in mountainous areas is related to dynamic aspect in addition to thermodynamic aspect. 2)We quantified the degree of freedom of extreme rainfall in the climate system, proposed a method for predicting future changes in stochastic rainfall. 3)Based on the relationship between total rainfall and rainfall within the flood arrival time and the combined occurrence probability of the two, we showed the existence of rainfall that causes high frequency and high inundation, which could not be understood by the probability evaluation of actual total rainfall. 4)We made it possible to discuss the efficient investment ratios for river management for main and tributary rivers, considering the uncertainty of the damage reduction effect of river management caused by the spatial distribution of rainfall.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 19H02241

Study on the generation mechanisms and nowcast of convective severe weather phenomena over diverse terrain by advanced methods
Grants-in-Aid for Scientific Research
01 Apr. 2019 - 31 Mar. 2022
YAMADA Yoshinori
This study has elucidated many new features of convective clouds. Major findings are the clarification of the actual condition of convective clouds, the formation and maintenance mechanism of a line-shaped precipitation system by organization of cumulonimbus clouds, the occurrence mechanism of severe phenomena, and a development of novel approach of short-range forecast of 1-minute precipitation amount by an ensemble of an advanced three-dimensional wind synthesis over a complex terrain, high-resolution numerical model experiments, polarization radar analysis, and a non-linear time series analysis. In particular, it is notable that a success of the elucidation of the time evolution of three-dimensional structures of convective clouds at a very high temporal resolution of 30 seconds by employing dual-Doppler wind synthesis that uses two cutting-edge phased array weather radars. Many of these accomplishments are published in peer reviewed papers and in conference presentations.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), 19H00815

Mechanical interactions between High-speed marine boundary layer flows and ocean waves
Grants-in-Aid for Scientific Research
01 Apr. 2018 - 31 Mar. 2022
Yasunori Watanabe
We developed computational models to simulate turbulence transitions over waves, formations of thermal boundary layers, and bubble-mediated turbulent flows, which provides physical mechanims contributing to sea-surface drag forces and momentum transfers between atmosphere and ocean. In wind tunnel experiemnts, for the first, we succesfully measured size spectra of the both of sea spray dispersed in atmosphere and air bubbles entrained into sea owing to wind wave breaking, which is related to the sea surface drag and bulk parameters. Contributions of gas dissolution from the entrained bubbles to air-sea gas exchages have been identified through physical and computational experiments. A new model of bubble drag in bubble clouds was also developed in this project, contributing physical understanding of wave-induced aeration process. In ocean observation, features of sea spray, bubble entrainment due to wind wave breaking, and their contributions to heat transfers across sea surfaces.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 18H03791

Development of Visualization Technology for Internal Structures of River Embankments and Civil Engineering Structures by Muon
Grants-in-Aid for Scientific Research
01 Apr. 2020 - 31 Mar. 2021
YAMADA TADASHI
The purpose of this research was to develop exploration technology by muons in order to visualize the internal structure of levees and civil engineering structures. The research is divided into four topics. As a result, we were able to establish a compact visualization technology which can measure in a short time.
The present research has succeeded in downsizing the detector to the size of a laptop and can easily visualize soil cover with thickness up to about 3 m. In addition, when a visualization experiment of the levees was carried out using a simultaneously counting type muon detector, the levee shape could be caught in about 8 hours. Moreover, we also succeeded in visualizing the infiltration situation of a soil tank in an experiment, so it is possible to utilize it as a new technology that can visualize the internal situation of the levee at the time of flood.
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Research (Pioneering), Chuo University, 20K20352

Newly Development of Inner Visualization for River Levee and Engineering Structures by using Mu-Particle.　　　　　　　　　　　　　　　
Grants-in-Aid for Scientific Research Challenging Research (Pioneering)
29 Jun. 2018 - 31 Mar. 2021
山田 正, 安田 浩保, 山田 朋人, 森島 邦博, 平川 大貴, 前田 健一
近年の極端降水現象により甚大な河川災害が繰り返されている。河川災害は、越流破堤と浸透破堤が二大要因であり、この現象を解明するためには、河川堤防の幾何形状と内部状態を空間的に連続して把握することが求められるが、既存の計測技術では不可能である。これに対し、近年注目されている宇宙線ミュー粒子を活用した探査技術を導入し、半導体技術を用いることで継続時間の大幅な短縮と形状の自由度を達成できる新たな可視化技術の確立を目的としている。
今年度は本研究において研究課題として設定した①～④のうち、①と②について実施する予定であったが、③についても取り組むことができた。
研究課題①ミュー粒子による検出器の計測対象の検討：計測対象を検討するために、水文学と地盤工学の土木工学の研究者と宇宙線を専門とする物理学者で定期的に会合を持ち、ミュー粒子検出器により初めて実像の把握が見込める土木構造物にどのようなものがあるのか議論した。その結果，検出器での検出結果と実像の実態を比較検証できる構造物であることが必須要件であるという結論になり、まずは試験体としての土層を製作し、その形状や浸水条件等を変更させながら試験計測を行うことになった。
研究課題②既存の同時計測型の検出器による試験計測：現場での試験計測を行うに当たっての基礎情報を入手するため、複数の河川において現地踏査を行い、現状の確認を行った。また、地下鉄道の漏水箇所を特定できる可能性についても試験計測を行った。
研究課題③光半導体型のミュー粒子検出器の設計と試作：基礎研究として、河川堤防の内部状態を把握するために必要な分解能と、その分解能を実現するために必要なミュー粒子数を捕捉する計測所要時間を概算するための数値計算を行った。これらの計算結果をもとに、光半導体型検出器の設計を行った。
Japan Society for the Promotion of Science, Challenging Research (Pioneering), Chuo University, 18H05334

Risk changes by age on disasters, water resources, food resources, and air pollution caused by climate change and their adaptation measures
Grants-in-Aid for Scientific Research
18 Jul. 2017 - 31 Mar. 2020
Yasunari Teppei J.
We carried out researches on “hazards”, “food resources”, “water resources”, and “air pollutions”, using climate models, satellite data, and reanalysis data together with some economic analyses, which are relevant to human sustainability in the future,. In terms of “air pollutions”, we found the climate and environmental factors related to large-scale wildfire occurrences, and further performed machine learning for its prediction as a preliminary research. The global simulations under the increased Siberian wildfire conditions by a climate model, MIROC/SPRINTARS, revealed that the number of days exceeding the environmental standard of PM2.5 in Japan, increased premature mortality, and its economic impact. The updated crop growth model, MATCRO, was incorporated to the latest MIROC. Another climate model simulation also revealed that the frequency of unprecedented occurrences on the observed precipitation was well explained with the temperature trend of 0.5 K per 100 years.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 17KT0066

Development of shipborne GNSS water vapor observation system
Grants-in-Aid for Scientific Research
30 Jun. 2017 - 31 Mar. 2020
Fujita Mikiko
The measuring of water vapor amount is essential for the understanding of the convective system that causes heavy precipitation. Especially for the heavy precipitation that occurs in the boreal summer around Japan, it's desired to observe the water vapor feature over the ocean at the leeward area that contains abundant water vapor. We developed the ship-borne analytic system for GNSS precipitable water vapor (PWV), which can estimate the PWV in real-time. Moreover, we investigated the impact of the oceanic water vapor for the forecast of the heavy precipitation event by the observing system simulation experiment.
As a result, the accurate GNSS PWV was confirmed by the developed system; that accuracy was similar to the previous study. In the impact investigation, the forecast of heavy precipitation was corrected by the assimilation of oceanic water vapor, in particular, the data was necessary around the leeward area where the water vapor transport was significant.
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Research (Exploratory), Japan Agency for Marine-Earth Science and Technology, 17K18963

Development of a road maintenance planning method for wide area road network considering river and sediment disaster risk
Grants-in-Aid for Scientific Research
01 Apr. 2017 - 31 Mar. 2020
Arimura Mikiharu
Typhoon No. 10, which struck Tohoku/Hokkaido in 2016, caused flooding of bridges and large-scale landslides due to flooding of rivers in various places, causing catastrophic damage to the main trunk roads that support local communities. For such unusual weather, it is necessary to build a wide-area road network with a view to the future. Conventionally, river basin plans and ground maintenance plans and road maintenance plans have not been linked sufficiently from the viewpoint of disaster prevention and mitigation. In this study, we used traffic big data for large-scale meteorological disasters to grasp the impact of damage to a wide area road network over a long period of time. In addition, a road improvement planning method was developed to improve the resilience of the wide area road network in consideration of the potential road damage risk due to river and sediment disasters.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Muroran Institute of Technology, 17H03318

Wide-area risk assessment of cold-regions geodisasters under climate change by multi-physical and multi-scale analysis
Grants-in-Aid for Scientific Research
01 Apr. 2016 - 31 Mar. 2020
ISHIKAWA Tatsuya
High-latitude zone like Hokkaido is an important region where it is expected to benefit and develop from global warming in future, while it is also expected that new types of geotechnical disasters, which never experienced before, will occur due to climate change. Therefore, in this study, we have constructed a theoretical system that reasonably explains the geotechnical disasters peculiar to snowy cold regions, which are different from the geotechnical disasters observed in warm regions, from the viewpoint of multiphysics (multiphase mechanics) and space-time multiscale by considering the interaction between thermal / hydraulic boundary condition changes and mechanical behavior in the normal to low temperature range. In addition, by using this theoretical system, we have proposed a hierarchical methodology that can evaluate the wide-area risk of geotechnical disasters in high-latitude cold regions occurred under near future weather conditions supposed by the climate change prediction.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 16H02360

Creation of natural-force-adaptive rivers based on the physical mechanism of long-term meandering evolution
Grants-in-Aid for Scientific Research
01 Apr. 2015 - 31 Mar. 2020
Shimizu Yasuyuki
This study systematizes a wide range of knowledge about the long-term dynamics of meandering, and builds the basic technology for realizing river development that makes full use of natural power and individuality. In particular, focusing on the meandering that determines the plane alignment of river topography, we deeply consider the fundamental mechanism of both short-term fluctuations due to sudden disasters and long-term topographical changes from past to future, and clarified the phenomena. In addition, we analyzed the various impacts on meandering, such as vegetation, presence of estuaries and river structures, diversity of meteorological and topographical geological conditions by theoretical analysis, field surveys, and simplified physical experiments. We also have constructed a computational model that can predict the meandering development transition considering various hydraulic conditions.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, 15H02267

Modifications of drag force and heat transfer across air-water mixing surface layers developed in a violent wave state
Grants-in-Aid for Scientific Research
01 Apr. 2015 - 31 Mar. 2019
Yasunori Watanabe
We found fundamental features of heat and gas transport in aerated ocean surface layers and modifications of surface drag in violent wave field through experimental parameterization of effects of sea sprays and bubbles entrained by wind wave breaking, computational identifications of heat and gas transfer owing to surface replacement under breaking waves, variable features of surface drag depending on transitions of three-dimensional vortex structures over ocean waves. As sea sprays dispersed in wind boundary layers disrupt the organization of the vortices formed over the breaking waves, causing transitions to fully developed turbulent boundary layer and modifications of surface drag. This process also changes the total momentum and heat fluxes between atmosphere and ocean.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 15H04043

Establishment of mathematical scientific river planning method which capable of responding to the possible maximum flood
Grants-in-Aid for Scientific Research
01 Apr. 2014 - 31 Mar. 2018
Yamada Tadashi
We suggested a way of mathematical scientific river planning excluding empirical factors. In conventional river planning, flood control standards such as design high water level are decided deterministically and single-valued, and the detail of river planning are based on these single-valued standards. However, there are uncertainties in hydrological quantities because of the differences in observation methods and their accuracy.
In this research, we suggested a distribution of water level (uncertainty) obtained from extreme value statistical theory and runoff analysis method considering the uncertainty of hydrological quantities, and showed the distribution is extremely useful as a material to decide the timing of evacuation information. In addition, we method to introduce the effect of sediment and the resistance of the river channel shape as uncertainty into river channel design. This kind of mathematical scientific planning method is corresponding to new social awareness.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Chuo University, 26249072

Global Hydrological Cycle in an Atmospheric General Circulation Model with Anthropogenic Modules
Grants-in-Aid for Scientific Research
01 Apr. 2015 - 31 Mar. 2017
YAMADA Tomohito, Yadu Pokhrel
Global hydrological cycle is affected by human activities such as irrigation, dam reservoir operation, groundwater pumping and domestic and industrial water consumptions. This study incorporated the land surface model including the dynamic human impact modules such into an Atmospheric General Circulation Model. Results showed that amount of irrigation water demand was approximately 3133 km3/yr which is comparable to observation and previous approaches based on land surface offline simulations and statistical models. The incorporation of the human impact modules into the AGCM showed reasonable sensitivity for surface air temperature against an original AGCM without those modules, and this is comparable to a previous study which adopts the impact of irrigation activity by surface water and heat fluxes as lower boundary conditions for AGCM.
Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), Hokkaido University, 15K18118

Study on features of snow clouds producing heavy snowfalls and gusts of wind by high-resolution observations and numerical models
Grants-in-Aid for Scientific Research
01 Apr. 2014 - 31 Mar. 2017
YAMADA Yoshinori, HARA Tabito
Studies based on observations and numerical models provided many findings on snow clouds producing heavy snowfalls and strong gust of wind. The analysis of Ku-band radar data revealed time changes in three-dimensional structures at convective scale of snow clouds at high spatial and temporal resolutions. Multi-Doppler radar analyses clarified characteristic airflow structures at meso β- and γ-scales in snow clouds producing heavy snowfalls, and wind recovery taking into account the surface vertical wind on complex orography suggested the importance of interaction between snow clouds and the orography for heavy snowfalls in Sapporo. A newly developed bulk microphysical model had better performance in reproducing snowfall patterns. Various processes important to the occurence and development of meso-α scale polar lows, sometimes accompanying heavy snowfalls and strong gust, were found by numerical experiments for winter seasons over past 30 years, using a regional model.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Japan, Meteorological Research Institute, 26242036

Momentum and heat transfer governed by micro-mechanics between atmonphere and ocean
Grants-in-Aid for Scientific Research
01 Apr. 2012 - 31 Mar. 2015
WATANABE Yasunori, YAMADA Tomohito, MORI Nobuhito, OTSUKA Junichi
A novel numerical simulator to compute local behaviors of sea sprays and entrained bubbles produced by micro ocean wave-breaking processes, based on the stochastic turbulence model, was developed in this study. The model was confirmed to reasonably reproduce heat and gas transfer through advection and diffusions processes via gas-liquid mechanical interactions.
Physical experiments for measuring the size distributions of sea-sprays and bubbles entrained into sea and the thermal radiation on the breaking-waves faces were performed in a wind wave flume. The momentum and heat transfer on the aerated ocean waves were found to be parametrized by the wind wave Reynolds number.The in-situ measurements for sea-sprays and air bubbles in ocean were also performed for characterizing mechanical contributions of the aerated ocean surface to the wave and current field.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 24360196

An experimental study on cyclic steps aiming for elucidation of the Mars' climate history
Grants-in-Aid for Scientific Research
01 Apr. 2012 - 31 Mar. 2014
YOKOKAWA Miwa, IZUMI Norihiro, HUGHES CLARKE John E., GREVE Ralf, YAMADA Tomohito, NAITO Kensuke, SUMIDA Takashi
"Spiral troughs" (cyclic step topography) observed at the upper part of Mars' north polar ice cap is considered to be closely related to the formation history of the npc and thus the climate history of Mars. In order to explore the formation mechanism of this step topography, we operated analog experiments using ice. We also did the other experiment of cyclic steps by the gravity flows analogue to the sediment waves in the deep sea environments whose internal structures are resemble to those of spiral troughs on Mars. A theoretical model of interfacial wave formation between the fluid and ice is also created. In the analog experiments, we have succeeded in forming a interfacial waves that develop at the interface between the fluid and the ice by the flow in upper flow-regime. Behavior of these steps was consistent with that predicted by the theoretical model.
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, Osaka Institute of Technology, 24654165

INTEGRATED RESEARCH ON LAND-ATMOSPHERE INTERACTION BY CLOUD RESOLVINGMODEL AND DETAILED LAND SURFACE PARAMETERS
Grants-in-Aid for Scientific Research
2010 - 2012
TANAKA Kenji, KANAE Shinjiro, HIGUCHI Atsushi, SHINODA Taro, YAMADA Tomohito, YOROZU Kazuaki, SOUMA Kazuyoshi
The latest version of the coupled model CReSiBUC has been developed with the cloud resolving model CReSS version 3.4 and the land surface model SiBUC with new irrigation and snow processes. Based on the analysis of spatial pattern correlation of NDVI, two numerical experiments with different vegetation parameters for 2011 and 2010 were executed to investigate the relationship between the land surface vegetation status and Asian Monsoon variability which caused the 2011 Chao Phraya river massive flood.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Kyoto University, 22246066

Estimation of hydro-meteorological forecast skills associated with land surface initializations
Grants-in-Aid for Scientific Research
2010 - 2011
YAMADA Tomohito
This study suggested that realistic land surface initializations can contribute to sub-seasonal hydro-meteorological forecast skills in addition to other initial conditions in atmosphere ocean processes. Furthermore the sub-seasonal forecast skill for the1988US drought was improved by incorporating influences of human activities such as irrigation on the land surface initializations.
Japan Society for the Promotion of Science, Grant-in-Aid for Young Scientists (B), Hokkaido University, 22760364

土壌水分の初期情報を用いた水文水資源量の準季節予報
科学研究費助成事業
2009 - 2010
山田 朋人
本研究は土壌水分の初期情報を用いた水文水資源量の準季節予報スキルの評価を目的としたものである.申請者らのこれまで全球気候モデル(General Circulation Model ; GCM)を用いた研究成果において,土壌水分の湿潤状態は夏の降水量偏差に重要な影響を与える要因であることが明らかにされてきた.一方,地表面以深の土壌水分は初期値の影響(メモリ)が1～2か月間程度持続することが示唆されており,これは大気のメモリ(1～2週間)と比較して極めて時定数の長いものである.これらの研究成果を合わせると,土壌水分の初期情報は1～2か月(準季節)予報の精度向上をもたらす可能性を有するが,これまで科学的噂の範疇を出るものではなかった.本研究において,人工衛星や現地観測により得られたデータと陸面過程モデルを用いて計算される"準観測"土壌水分データを初期値としたGCMによる過去10年間の予報実験を行った結果,準季節スケールの降水量をはじめとする水文水資源量の予報精度がある程度改善されることが判明した.特に,1988年に北米を襲った大旱魃や同地域に大洪水をもたらした豪雨を2週間前以上前から予測するには,土壌水分の初期情報が必要不可欠であるという結果が得られた.
日本学術振興会, 研究活動スタート支援, 北海道大学, 21860002

Bachelor's degree program, School of Engineering

Master's degree program, Graduate School of Engineering

Doctoral (PhD) degree program, Graduate School of Engineering