研究者データベース

山田 朋人(ヤマダ トモヒト)
工学研究院 土木工学部門 社会基盤マネジメント
准教授

基本情報

所属

  • 工学研究院 土木工学部門 社会基盤マネジメント

職名

  • 准教授

学位

  • 博士(工学)(東京大学)

ホームページURL

科研費研究者番号

  • 10554959

J-Global ID

研究キーワード

  • 土壌水分   極端現象   全球気候モデル   陸面モデル   全球再解析データ   人工衛星   地球水循環   人間活動   準季節予報   大気陸面相互作用   予報スキル   予測可能性   水文気象   陸面状態   衛星植生観測情報   植生パラメータ   双方向ネスティング   海洋科学   モンスーン変動   陸面過程   自然現象観測・予測   海洋物理   計算物理   モンスーン   水工水理学   雲解像モデル   

研究分野

  • 社会基盤(土木・建築・防災) / 水工学
  • 社会基盤(土木・建築・防災) / 水工学

職歴

  • 2009年04月 - 現在 北海道大学 工学(系)研究科(研究院) 工学(系)研究科(研究院) 准教授
  • 2007年04月 - 2009年03月 NASAゴッダードスペースフライトセンター/メリーランド大学Baltimore校 Global Modeling and Assimilation Office Research Associate

研究活動情報

論文

  • SUPRABA Intan, YAMADA Tomohito J
    水工学論文集 土木学会水工学委員会 編 59 I_151 - 156 土木学会 2015年 [査読無し][通常論文]
  • 佐々木翔太, 山田正, 山田朋人
    水文・水資源学会誌 27 4 170 - 181 THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES 2014年07月05日 [査読無し][通常論文]
     
    本研究は人体における放射性同位体の原子数,放射能強度,内部被曝総量を計算するために複雑な人体のメカニズムを必要としない,水文学的モデルを用いた理解容易な方法論を提案することを目的とする.国際放射線防護委員会による既往研究は人体を忠実に再現した厳密なモデルが採用され,放射線医学の専門家の間では標準的なモデルと考えられている.既存の方法は厳密であるが,水文学の研究者を含む一般の研究者にとっては非常に複雑で全体を理解するには困難である.本研究は放射性同位体の経口摂取による被曝を,人体を単一の組織と見なして計算した.この手法によって複雑な人体のメカニズムを考慮せずに,人体における放射能強度について,ホールボディカウンタによる実測値と本研究によって得られた解析解が同等の結果を与えることが示された.
  • 大塚淳一, 渡部靖憲, 田代晃基, 大山高弘, 猿渡亜由未, 山田朋人
    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年 [査読無し][通常論文]
     
    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.
  • 渡部靖憲, 田代晃基, 大塚淳一, 大山高弘, 山田朋人
    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年 [査読無し][通常論文]
     
    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.
  • 内山雄介, 松川大佑, 神吉亮佑, 馬場康之, 森信人, 水谷英朗, 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) 70 2 I.446-I.450 (J-STAGE) - I_450 Japan Society of Civil Engineers 2014年 [査読無し][通常論文]
     
    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.
  • 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年 [査読無し][通常論文]
     
    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.
  • Suseno Dwi, Prabowo Yuga, Yamada Tomohito
    Journal of hydrometeorology 14 6 1922 - 1932 Amer meteorological soc 2013年12月 [査読無し][通常論文]
     
    A rainfall estimation method was developed based on the statistical relationships between cloud-top temperature and rainfall rates acquired by both the 10.8-m 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.
  • 河野剛典, 河野剛典, 山田朋人, 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 2013年09月17日 [査読無し][通常論文]
     
    水資源の安定及び持続的な確保は水ストレスを軽減させる上で必要不可欠である一方,農業による灌漑やダム湖への貯水などの人間活動が流域内の水収支に及ぼす影響は非常に大きいと考えられる.このような背景から全球スケールを対象とし人間活動の影響を考慮した陸面過程を再現するモデルが近年開発された.本研究は同モデルを北海道全域に適用し,その特徴並びに妥当性を明らかにするとともに,将来的には日本全域において水資源の効率的な活用方法を提示しうるモデルの構築を目指すものである.本論文では農業用灌漑活動が水熱収支に与える影響に特化した評価を行った.またモデルの再現するダム放流量については大雪ダムを対象に観測データとの比較を実施したところ年間取水量に関してある程度の妥当性が示された.
  • Yamada Tomohito J, Kanae Shinjiro, Oki Taikan, Koster Randal D
    Hydrological Sciences Journal - Journal des Sciences Hydrologiques 58 6 1276 - 1286 Taylor & Francis 2013年08月01日 [査読無し][通常論文]
     
    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 precipitationand thus the timing of monsoon onset.
  • 福島大輝, 山田朋人, 宮崎真
    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年 [査読無し][通常論文]
     
    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.
  • 山田 朋人, 秦 佳弘
    土木学会論文集B1(水工学) 69 4 I_397 - I_402 Japan Society of Civil Engineers 2013年 [査読無し][通常論文]
     
    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.
  • 内藤健介, 泉典洋, 横川美和, 山田朋人
    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年 [査読無し][通常論文]
     
    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.
  • 渡部大和, 山田朋人, 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年 [査読無し][通常論文]
     
    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.
  • 山原康希, 山田朋人, 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年 [査読無し][通常論文]
     
    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.
  • 北野慈和, 山田朋人, 泉典洋
    地球環境研究論文集 20 5 I.205-I.210 - I_210 Japan Society of Civil Engineers 2012年09月13日 [査読無し][通常論文]
     
    日本の豪雨イベントを引き起こすメソスケールの現象の一つとして線状降水帯が挙げられるが,その物理機構については不明な点が多い。線状降水帯の形成過程を解明することは防災の観点から非常に重要である。そこで本研究では,線状降水帯が発生する条件の一つである不安定な成層をした大気場の空間特性を解析的に明らかにした。解析では,問題を単純化するために降水や熱力学的な効果は考えず,大気場における鉛直方向の擾乱の水平分布のみを考慮している。この解析により擾乱の発達とフルード数及び密度差に関する無次元パラメータとの関係が明らかとなり,これらと線状降水帯との関係性について考察した。
  • Tomohito J. Yamada, Myong-In Lee, Masao Kanamitsu, Hideki Kanamaru
    JOURNAL OF HYDROMETEOROLOGY 13 3 1142 - 1148 2012年06月 [査読無し][通常論文]
     
    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.
  • Yasunori Watanabe, Yuta Mitobe, Ayumi Saruwatari, Tomohito Yamada, Yasuo Niida
    COASTAL ENGINEERING JOURNAL 54 1 1250002.1-1250002.17  2012年03月 [査読無し][通常論文]
     
    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.
  • 和田卓也, 山田朋人, SUSENO Yuga Dwi Prabowo
    水工学論文集(CD-ROM) 56 4 ROMBUNNO.67 - I_402 Japan Society of Civil Engineers 2012年02月20日 [査読無し][通常論文]
     
    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.
  • SUSENO Dwi, Prabowo Yuga, YAMADA Tomohito J
    土木学会論文集B1(水工学) 68 4 I_175 - I_180 Japan Society of Civil Engineers 2012年 [査読無し][通常論文]
     
    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.
  • Dwi Prabowo Yuga Suseno, Tomohito J. Yamada
    REMOTE SENSING LETTERS 3 8 737 - 746 2012年 [査読無し][通常論文]
     
    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.
  • 和田卓也, 山田朋人
    水工学論文集(CD-ROM) 55 4 ROMBUNNO.81 - I_486 Japan Society of Civil Engineers 2011年02月22日 [査読無し][通常論文]
     
    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.
  • YAMADA Tomohito J, KOSTER Randal D, KANAE Shinjiro, OKI Taikan
    水工学論文集(CD-ROM) 54 ROMBUNNO.56  2010年02月22日 [査読無し][通常論文]
  • Tomohito J. Yamada, Randal D. Koster, Shinjiro Kanae, Taikan Oki
    MONTHLY WEATHER REVIEW 135 7 2674 - 2687 2007年07月 [査読無し][通常論文]
     
    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.
  • 山田朋人, 鼎信次郎, 沖大幹
    水工学論文集(CD-ROM) 51 ROMBUNNO.53 - 318 Japan Society of Civil Engineers 2007年02月22日 [査読無し][通常論文]
     
    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.
  • GUO Zhichang, DIRMEYER Paul A, KOSTER Randal D, BONAN Gordon, CHAN Edmond, COX Peter, GORDON C. T, KANAE Shinjiro, KOWALCZYK Eva, LAWRENCE David, LIU Ping, LU Cheng‐Hsuan, MALYSHEV Sergey, MCAVANEY Bryant, MCGREGOR J. L, MITCHELL Ken, MOCKO David, OKI Taikan, OLESON Keith W, PITMAN Andrew, SUD Y. C, TAYLOR Christopher M, VERSEGHY Diana, VASIC Ratko, XUE Yongkang, YAMADA Tomohito
    J Hydrometeorol 7 4 611 - 625 2006年08月 [査読無し][通常論文]
  • KOSTER Randal D, GUO Zhichang, DIRMEYER Paul A, BONAN Gordon, CHAN Edmond, COX Peter, DAVIES Harvey, GORDON C. T, KANAE Shinjiro, KOWALCZYK Eva, LAWRENCE David, LIU Ping, LU Cheng‐Hsuan, MALYSHEV Sergey, MCAVANEY Bryant, MITCHELL Ken, MOCKO David, OKI Taikan, OLESON Keith W, PITMAN Andrew, SUD Y. C, TAYLOR Christopher M, VERSEGHY Diana, VASIC Ratko, XUE Yongkang, YAMADA Tomohito
    J Hydrometeorol 7 4 590 - 610 2006年08月 [査読無し][通常論文]
  • KANAE Shinjiro, HIRABAYASHI Yukiko, YAMADA Tomohito, OKI Taikan
    J Clim 19 8 1450 - 1460 2006年04月15日 [査読無し][通常論文]
  • 山田朋人, 鼎信次郎, 沖大幹
    水工学論文集 49 1 1 - 6 Japan Society of Civil Engineers 2005年02月01日 [査読無し][通常論文]
     
    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.
  • Koster RD, Dirmeyer PA, Guo Z, Bonan G, Chan E, Cox P, Gordon CT, Kanae S, Kowalczyk E, Lawrence D, Liu P, Lu CH, Malyshev S, McAvaney B, Mitchell K, Mocko D, Oki T, Oleson K, Pitman A, Sud YC, Taylor CM, Verseghy D, Vasic R, Xue Y, Yamada T, GLACE Team
    Science (New York, N.Y.) 305 5687 1138 - 1140 2004年08月 [査読有り][通常論文]
  • 山田朋人, 鼎信次郎, 沖大幹
    水工学論文集 48 1 223 - 228 Japan Society of Civil Engineers 2004年02月01日 [査読無し][通常論文]
     
    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.

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    課程区分 : 修士課程
    開講学部 : 工学院
    キーワード : Shallow-Water Theory, Turbulent Flows, Geostrophic Flows, Climate Model
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    開講学部 : 大学院共通科目
    キーワード : Shallow-Water Theory, Turbulent Flows, Geostrophic Flows, Climate Model
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    課程区分 : 博士後期課程
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    課程区分 : 博士後期課程
    開講学部 : 工学院
  • 環境流体力学応用特論
    開講年度 : 2018年
    課程区分 : 博士後期課程
    開講学部 : 工学院
    キーワード : Shallow-Water Theory, Turbulent Flows, Geostrophic Flows, Climate Model
  • 環境流体力学基礎特論
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    課程区分 : 博士後期課程
    開講学部 : 工学院
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    キーワード : 流れ,渦,波,自然災害,気候変動


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