MF研究者総覧

研究者データベース

詳細
川島　正行(カワシマ　マサユキ)
低温科学研究所　水・物質循環部門
助教
researchmap個人ページ
Last Updated :2023/12/05

基本情報

所属

  • 低温科学研究所　水・物質循環部門

職名

  • 助教

学位

  • 理学博士（東京大学）

ホームページURL

J-Global ID

プロフィール

  • 北海道大学低温科学研究所助教

研究キーワード

  • 台風   豪雪   豪雨   ドップラ-レ-ダ-   雲解像モデル   熱力学的リトリ-バル   シア不安定   筋状降雪雲   気象学   大気現象   温帯低気圧   降雪   前線   渦状降雪雲   下層雲   北極海   オホーツク海   乱流フラックス   

研究分野

  • 自然科学一般 / 大気水圏科学
  • 環境・農学 / 環境動態解析

担当教育組織

職歴

  • 2001年05月 - 2013年03月 防災科学技術研究所 客員研究員(兼任)
  • 2007年04月 - 2011年 北海道大学 低温科学研究所 助教
  • 1996年04月 - 2007年03月 北海道大学 低温科学研究所 助手

所属学協会

  • Meteorological Society of Japan   日本気象学会   

研究活動情報

論文

  • Tsutomu Watanabe, Marie Takagi, Kou Shimoyama, Masayuki Kawashima, Naoyuki Onodera, Atsushi Inagaki
    Boundary-Layer Meteorology 181 1 39 - 71 2021年10月 [査読有り]
     
    AbstractA double-distribution-function lattice Boltzmann model for large-eddy simulations of a passive scalar field in a neutrally stratified turbulent flow is described. In simulations of the scalar turbulence within and above a homogeneous plant canopy, the model’s performance is found to be comparable with that of a conventional large-eddy simulation model based on the Navier–Stokes equations and a scalar advection–diffusion equation in terms of the mean turbulence statistics, budgets of the second moments, power spectra, and spatial two-point correlation functions. For a top-down scalar, for which the plant canopy serves as a distributed sink, the variance and flux of the scalar near the canopy top are predominantly determined by sweep motions originating far above the canopy. These sweep motions, which have spatial scales much larger than the canopy height, penetrate deep inside the canopy and cause scalar sweep events near the canopy floor. By contrast, scalar ejection events near the canopy floor are induced by coherent eddies generated near the canopy top. The generation of such eddies is triggered by the downward approach of massive sweep motions to existing wide regions of weak ejective motions from inside to above the canopy. The non-local transport of scalars from above the canopy to the canopy floor, and vice versa, is driven by these eddies of different origins. Such non-local transport has significant implications for the scalar variance and flux budgets within and above the canopy, as well as the transport of scalars emitted from the underlying soils to the atmosphere.
  • Masayuki Kawashima
    Journal of the Atmospheric Sciences 2021年09月17日 [査読有り][通常論文]
     
    AbstractProminent cirrus cloud banding occurred episodically within a northern cirrus canopy of Typhoon Talim (2017) during its recurvature. The generation mechanisms of the cirrus bands and low static-stability layers that support the bands are investigated using a numerical simulation with the Advanced Research Weather Research and Forecasting Model. Inspection of model output reveals that thin layers of near-neutral to weakly unstable static stability are persistently present in the upper and lower parts of the upper-level outflow, and shallow convection aligned along the vertical shear vector is prevalent in these layers. The cirrus banding occurs as the lowered outflow from the weakening storm ascends slantwise over a midlatitude baroclinic zone, and updrafts of the preexisting shallow convection in the upper part of the outflow layer become saturated. It is shown that the strong outflow resulting from violation of gradient-wind balance in the core region, by itself, creates the low static-stability layers. Analyses of potential temperature and static stability budgets show that the low static-stability layers are created mainly by the differential radial advection of radial thermal gradients on the vertical edges of the outflow. The radial thermal gradients occur in response to the outward air parcel acceleration in the core region and deceleration in the outer region, which, by inducing compensating vertical mass transport into and out of the outflow, act to tilt the isentropes within the shear layers. The effects of environmental flow and cloud radiative forcing on the cirrus banding are also addressed.
  • Tsutomu Watanabe, Kou Shimoyama, Masayuki Kawashima, Yasuko Mizoguchi, Atsushi Inagaki
    Boundary-Layer Meteorology 176 1 35 - 60 2020年07月 [査読有り]
     
    AbstractA central-moments-based lattice Boltzmann model for large-eddy simulation of neutrally-stratified turbulent flows is described. Through comparative simulations of the airflow within and above a homogeneous plant canopy, the performance of the model is evaluated with respect to a conventional large-eddy-simulation model based on the incompressible Navier–Stokes equations. Simulated turbulence statistics, such as the mean velocity, velocity variances, velocity skewness, and power spectra, are shown to be almost identical between the two models. The spatial structure of coherent eddies and their maintenance processes are also confirmed to be properly represented by the lattice Boltzmann method through analysis of the turbulence kinetic energy budget and spatial two-point correlation functions. Using the simulated results, the energetics of the streamwise-elongated streaky structures commonly observed over vegetation and urban canopies are examined. While the short-wavelength components of the shear-generated streamwise kinetic energy are redirected rapidly by pressure to the lateral and vertical velocity components, long-wavelength energy tends to remain in the streamwise velocity component, which is dissipated in relatively slower processes. Consequently, the streaky structures persist in the streamwise velocity component.
  • Leah S. Campbell, W. James Steenburgh, Yoshinori Yamada, Masayuki Kawashima, Yasushi Fujiyoshi
    Monthly Weather Review 146 7 2201 - 2220 2018年07月01日 [査読有り]
     
    Abstract Sea-effect snowstorms generated over the Sea of Japan produce consistent and often heavy snowfall throughout the winter season, impacting downstream communities in northern and central Japan. Here, we use observations and Weather Research and Forecasting (WRF) Model simulations to examine the precipitation distribution produced by transverse-mode sea-effect snowbands that interacted with the mountainous terrain circumscribing Ishikari Bay, Hokkaido Island, Japan, on 12 January 2014. The bands observed here were horizontal convective rolls aligned normal to the mean flow and were ~10 km wide and up to ~100 km long. The bands approached Ishikari Bay at intervals of ~10–16 min, intensifying as they progressed through a quasi-stationary, elongated enhancement region that paralleled the Shakotan Peninsula and extended into the Ishikari plain. Hydrometeor advection, through an ascent region over the northeast slope of the Shakotan Peninsula, and along clockwise-turning trajectories steered by the boundary layer directional shear, contributed to sustained precipitation enhancement along a curve in the elongated enhancement region near the entrance to Ishikari Bay. Downstream, orographic flow deflection by the coastal mountains, likely accentuated by thermal and roughness gradients along the Shakotan Peninsula’s shoreline, produced convergence and ascent along the elongated enhancement region. This study demonstrates the impact of downstream topography on sea-effect snowstorms and has implications for improving the prediction of snowfall in this and other lake- and sea-effect regions.
  • Masayuki Kawashima
    Journal of the Atmospheric Sciences 73 7 2803 - 2836 2016年07月01日 [査読有り]
     
    Abstract Realistic mesoscale model simulations using the Weather Research and Forecasting (WRF) Model and idealized dry simulations were used to study the mechanisms responsible for the formation and evolution of wide cold-frontal rainbands (WCFRs) associated with a wintertime cyclone that moved onto the Washington coast. The WRF simulation reproduced observed characteristics of three successively formed WCFRs, including their spacing and movement as well as the timing of the formation of two WCFRs behind the first. Sensitivity experiments showed that melting-induced cooling in the stratiform precipitation area behind the surface cold front was essential for the formation of the first and second WCFRs, whereas the third WCFR was formed by the release of potential instability within an ascent forced by upper-level frontogenesis. Enhanced frontal updrafts responsible for the first and second WCFRs were created by a superposition of a broad updraft caused by frontal dynamics and upward-propagating gravity waves generated by the melting-induced cooling. The dry simulations forced by specified cooling revealed specific mechanisms for the wave generation and the evolution of the first and second WCFRs. The gravity waves were generated at the intersection of the low-level frontal zone and the melting layer, where strong vertical shear of the cross-front wind and upshear-sloped cooling by melting cooperatively enhanced the wave generation. The formation of the second WCFR behind the first and subsequent dissipation of these WCFRs was attributed to the evolution of a wave pattern associated with the evolution of cross-front flow above the frontal zone.
  • Raghava Yakkala Yagnesh, Nakamura Tomohiro, Mitsudera Humio, Kawashima Masayuki
    Hydrological Research Letters 8 2 84 - 89 THE JAPAN SOCIETY OF HYDROLOGY AND WATER RESOURCES 2014年 [査読有り]
     
    A thick snow band often forms along the Okhotsk Sea coast of Hokkaido Island, northern part of Japan. Numerical simulations were made to investigate the formation and maintenance mechanisms of a long-lasted snow band appeared on 26th of December 2008 using Weather Research and Forecasting Model (WRF). The snow band was simulated along the coast of Hokkaido Island, moved offshore toward the Sea of Okhotsk, where it intensified, and was sustained for one and a half days. The results show that Sakhalin Island plays an important role in the maintenance of a convergence line and thus the snow band. Cold air advection from Sakhalin Island produces a strip of warm air between the advected cold air and Hokkaido Island and thus controls the location of the snow band, while topographic blocking by Sakhalin creates the lower level convergence at the Soya Strait and hence enhances the snow band. Temperature and surface-roughness contrast between Hokkaido Island and the Sea of Okhotsk appear to be also important for the initial formation of the snow band.
  • 3次元ドップラーライダー観測データに基づいた洋上風車の最適配置
    須賀伸介, 内山政弘, 松本幸雄, 藤吉康志, 川島正行, 藤原忠誠
    太陽エネルギー 38 67 - 74 2012年06月 [査読有り][通常論文]
  • 藤吉康志, 岸寛人, 大竹秀明, 川島正行
    天気 58 8 705 - 710 日本気象学会 2011年08月 [査読有り][通常論文]
     
    1998年から2002年の暖候期の「ひまわり」の可視画像を調べたところ,日本海上を層雲域が北東方向に移動する際,北海道西岸沖にのみ雲が存在しないという再現性のある雲分布が見出された.この特異な水平分布には,奥尻島によって発生するフェーンの局所的効果に加えて,北海道全体で作られる気流系の影響が大きいことが,WRF(Weather Research and Forecasting)-ARWを用いたシミュレーション結果から示唆された.
  • Namiko Sakurai, Shuichi Mori, Masayuki Kawashima, Yasushi Fujiyoshi, Hamada Jun-Ichi, Shingo Shimizu, Hironori Fudeyasu, Yoshikazu Tabata, Wendi Harjupa, Hiroyuki Hashiguchi, Manabu D. Yamanaka, Jun Matsumoto, Emrizal, Fadli Syamsudin
    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN 89 4 341 - 361 2011年08月 [査読有り][通常論文]
     
    This study describes the three-dimensional structure and migration process of a westward-migrating precipitation system with a diurnal cycle observed on 10 November 2006 in west Sumatera as based on dual-Doppler radar analysis, rawinsonde data, and surface data. The location of convective cell generation over land in the daytime and the timing of an evening change in the migration direction of precipitation systems from landward to seaward were influenced by local circulation: in the morning, an isolated convective cell generated near the west coast propagated inland (toward the mountains) via the successive generation of new convective cells over the sea breeze. In the afternoon, convective cells in a precipitation system were generated over the western slopes of the mountains surrounding Lake Maninjau by thermally induced local circulation and the slope effect. In the evening, precipitation systems located over the mountains started to propagate toward the sea (westward) in response to a change in local circulation from landward to seaward winds. Subsequently, precipitation systems were newly generated over the sea near the west coast of Sumatera Island, merging with the systems that originated over land. These two sets of systems formed a larger system (long axis > 100 km) than that over land (long axis of several tens of kilometers). The expanded precipitation system had a convective region with a long axis oriented parallel to the west coast of Sumatera Island and a short axis (similar to 7 km) oriented perpendicular to the west coast at the leading edge of the system. The echo top height of the system was located at approximately 13 km and an anvil moved faster than the convective region above 6 km in height. The convergence was formed by an easterly wind component in the system and a southerly wind component over the sea around the leading edge of the system at the lowest layer. The expanded system migrated farther offshore at a speed of about 5 m s(-1) via the self-replication of convective cells over the convergence at the leading edge of the system and via advection by ambient wind in the lower troposphere. The convergence regions at the leading edge of the system were continuously strengthened by downward transportation of horizontal momentum below 4 km, meaning that the system could be maintained for a long time and migrate offshore for a long distance.
  • Masayuki Kawashima
    Journal of the Atmospheric Sciences 68 4 878 - 903 American Meteorological Society 2011年04月01日 [査読有り]
     
    The effects of variations in low-level ambient vertical shear and horizontal shear on the alongfront variability of narrow cold frontal rainbands (NCFRs) that propagate into neutral and slightly unstable environments are investigated through a series of idealized cloud-resolving simulations. In cases initialized with slightly unstable sounding and weak ambient cross-frontal vertical shears, core-gap structures of precipitation along NCFRs occur that are associated with wavelike disturbances that derive their kinetic energy mainly from the mean local vertical shear and buoyancy. However, over a wide range of environmental conditions, core-gap structures of precipitation occur because of the development of a horizontal shear instability (HSI) wave along the NCFRs. The growth rate and amplitude of the HSI wave decrease significantly as the vertical shear of the ambient cross-front wind is reduced. These decreases are a consequence of the enhancement of the low-level local vertical shear immediately behind the leading edge. The strong local vertical shear acts to damp the vorticity edge wave on the cold air side of the shear zone, thereby suppressing the growth of the HSI wave through the interaction of the two vorticity edge waves. It is also noted that the initial wavelength of the HSI wave increases markedly with increasing horizontal shear. The local vertical shear around the leading edge is shown to damp long HSI waves more strongly than short waves, and the horizontal shear dependency of the wavelength is explained by the decrease in the magnitude of the vertical shear relative to that of the horizontal shear.
  • Shuichi Mori, Jun-Ichi Hamada, Namiko Sakurai, Hironori Fudeyasu, Masayuki Kawashima, Hiroyuki Hashiguchi, Fadli Syamsudin, Ardhi A. Arbain, Reni Sulistyowati, Jun Matsumoto, Manabu D. Yamanaka
    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN 89A 61 - 81 2011年02月 [査読有り][通常論文]
     
    An overview of convective activity during the HARIMAU2006 campaign conducted from 26 October to 27 November 2006 was presented, focusing on the differences between coastal land/sea and inactive/active phases of intraseasonal variation (ISV) based on observations using an X-band Doppler radar (XDR) and intensive soundings at Sumatera Island. Diurnal variation (DV) in coastal convections and formation of the coastal heavy rainband (CHeR) along Sumatera Island were also examined in terms of diurnal land-sea migration of coastal convective systems. Convection in the ISV inactive period (PP1) contained convective rain fractions nearly twice as much as stratiform rain fractions, whereas that in the ISV active period (PP2) comprised convective and stratiform elements almost equally. Vertical profiles of radar echo coverage for stratiform rain during PP2 were greater than those during PP1, especially in the lower troposphere over the sea. The radar echo coverage for convective rain over the sea during both periods was nearly double that over land from the near surface up to 6 km high. Convection was generated in the southwestern foothills of the mountain range in the early afternoon (12-15 Local Time, LT). Part of the convective system remained over the coastal land and exhibited weak reflectivity until the next morning. The other part migrated offshore at a speed of approximately 4 m s(-1) and intensified until around 21 LT while still offshore. Additional convective cells also developed offshore in the early morning hours, independent of those that formed over land. Results suggested that the CHeR along Sumatera Island is dictated by diurnal variations in coastal convective development and consists of the following phases: 1) migration of convection away from the coastal land and its redevelopment in the late evening, and 2) additional generation of convection just offshore during the early morning hours.
  • Masayuki KAWASHIMA, Yasushi FUJIYOSHI, Masayuki OHI, Shuichi MORI, Namiko SAKURAI, Yoshiko ABE, Wendi HARJUPA, Fadli SYAMSUDIN, Manabu D. YAMANAKA
    Journal of the Meteorological Society of Japan. Ser. II 89A 239 - 257 2011年 [査読有り][通常論文]
     
    In this study, the processes responsible for an intense wind event that occurred in west Sumatera on November 19, 2006, during the first campaign of the Hydrometeorological ARay for Isv-Monsoon AUtomonitoring (HARIMAU) were investigated. Strong winds of 17 m s(-1) a sudden temperature drop of 5 K were observed at an X-band Doppler radar site associated with the passage of a convective system, and some houses were severely damaged. The convective system developed under an environment of strong low-level easterly vertical shear associated with the easterly region of an equatorial Rossby wave. The northern part of the convective system possessed qualitatively similar structures to midlatitude bow echoes, including the convex shape of the convective line, a descending rear-inflow jet positioned at its apex, and mesoscale vortices on both sides of the rear-inflow jet. The low-level wind behind the convective system formed a channel of strong easterly wind as it passed through an area of relatively low topography in the mountain range. The enhanced easterly wind was thought to contribute to the formation of the bow echo-like structure in the northern part of the convective system. This easterly rear-inflow jet was further accelerated in the convective system and descended near the leading edge, forming divergent strong winds at the surface. The sounding data that were taken after the passage of the convective system indicated that dry air appeared in the lower troposphere associated with an enhancement of the southerly component of the wind. An analysis of objective reanalysis data suggests that the southerly was probably associated with westward-propagating mixed Rossby-gravity waves with a period of approximately 5 days. It is suggested that the dry air intruded into the convective system across the back edge of the precipitation area and caused enhanced evaporative cooling, which resulted in the effective downward transport of the enhanced easterly momentum.
  • Hideaki Ohtake, Masayuki Kawashima, Yasushi Fujfyoshi
    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN 87 2 289 - 306 2009年04月 [査読有り][通常論文]
     
    During cold-air outbreaks in winter, a thick cloud band frequently appears over the northern Sea of Japan and produces localized heavy snowfall in the western coastal region of Hokkaido Island, northern part of Japan. The formation mechanism of this thick cloud band is investigated through a series of nonhydrostatic numerical simulations with a horizontal grid spacing of 5 km. The control simulation well reproduces the characteristics of an observed cloud band. The cloud band forms between relatively warm north-northwesterly winds on the northeast side and relatively cold northwesterly winds on the southwest side. Sensitivity experiments in which upstream topography is modified indicate that the formation and intensification of the cloud band depend on the following two effects; one is the effect of a specific mountain located near the coastline in the middle part of Russia's Sikhote-Alin mountain range (SAMR), and the other is the effect of large-scale topography along the SAMR on synoptic-scale low-level cold northwesterlies. The specific mountain deflects the cold airflow and immediately a convergence zone forms downstream of the specific mountain, where the cloud band is initiated. On the northeastern side of this mountain, the Froude number is estimated to be about 0.4 from relatively high topography (similar to 1.2 km), stable stratification (similar to 0.02 s(-1)), and synoptic-scale wind speed of 10 m s(-1). Thus, the relatively high topography strongly blocks a low-level cold air, whereas an upper air with high potential temperature flows downward over the sea. In contrast, on the southwestern side of the mountain, a low-level cold air can pass over the topography, because the Froude number is estimated to be about 1.6 from relatively low topography (similar to 0.8 km) and weak stable stratification (similar to 0.008 s(-1)). These two airs with different potential temperature create a mesoscale frontal zone over the sea, which causes the further development of the thick cloud band initiated by the coastal specific mountain in the SAMR.
  • Namiko Sakurai, Masayuki Kawashima, Yasushi Fujiyoshi, Hiroyuki Hashiguchi, Toyoshi Shimomai, Shuichi Mori, Jun-ichi Hamada, Fumie Murata, Manabu D. Yamanaka, Yudi Iman Tauhid, Tien Sribimawati, Budi Suhardi
    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN 87 1 157 - 170 2009年02月 [査読有り][通常論文]
     
    There is a diurnal cycle of systematic cloud migration over Sumatera Island, i.e., cloud systems developing in the mountainous area in the afternoon migrate westward and/or eastward for several hundreds of kilometers (about 500 km) from night to morning. The regional characteristics and internal structure of migratory cloud systems with a diurnal cycle over Sumatera Island during CPEA-I were examined using data from an X-band Doppler radar (XDR), a VHF wind profiler (Equatorial Atmosphere Radar (EAR)), rawinsondes, and Geostationary Operational Environmental Satellite (GOES9). During CPEA-I, the cloud system had a horizontal scale of several hundred kilometers and migrated both westward and eastward over nearly all of Sumatera Island except for the southernmost part. The cloud system migrated only westward over southernmost Sumatera Island during CPEA-I. From a case study on April 17 and 18, 2004, precipitation systems with horizontal scales of several tens of kilometers were observed in a cloud system by XDR, and they migrated in a direction similar to that of the cloud system at a speed of about 3 m s(-1), which roughly corresponded to the wind direction and speed in the lower troposphere. Convective precipitation was observed mainly in the forward region of the precipitation systems, and stratiform precipitation was observed in the rearward region. The convective precipitation successively generated new convective cells in front of old convective cells. These results suggest that the migratory mechanism of the precipitation systems is self-replication of convective cells and the advection of background wind in the lower troposphere.
  • Toshiaki Kozu, Yasu-Masa Kodama, Yoshiaki Shibagaki, Toyoshi Shimomai, Masayuki Kawashima, Simon P. Alexander
    EARTH PLANETS AND SPACE 61 4 535 - 544 2009年 [査読有り][通常論文]
     
    Vertical wind variations in the Upper Troposphere and Lower Stratosphere (UTLS) measured by the Equatorial Atmosphere Radar (EAR) at Kototabang, Sumatra, between 2003 and 2005 but mainly in 2004. have been statistically analyzed to study the characteristics of wind variances associated with convective activity. which is related to gravity wave generation and propagation. The analyses are intended to characterize relatively short period disturbances of less than 12 hours and an energy propagation direction of a relatively high elevation angle. and to relate vertical wind variations to convective activity close to the EAR. Correlation analyses between vertical wind variations and rainfall show that the wind variances have a clear diurnal variation indicating probable effects of tropospheric convection. They also show some intraseasonal variation. However, there are no significant correlations with the out-going long-wave Radiation (OLR) anomaly. The correlations between variances at UT and LS suggest that the UTLS coupling of vertical wind variation through upward propagation of gravity wave is similarly evident in the afternoon during both the active and the inactive phase of OLR that is a proxy of large-scale convective activity.
  • HARIMAU Radar-Profiler Networkover the Indonesian MaritimeContinent: A GEOSS earlyachievement for hydrological cycle and disaster prevention
    Yamanaka, M. D, H. Hashiguchi, S. Mori, P. Wu, F. Syamsudin, T. Manik, Hamada J.-I, M.K.Yamamoto, M. Kawashima, Y. Fujiyoshi, N. Sakurai, M. Ohi, R. Shirooka, M. Katsumata, Y. Shibagaki, T. Shimomai, Erlansyah, W. Setiawan, Bambang Tejasukmana, Yusuf S, Djajadihardja, J. T. Anggadiredja
    Journal ofDisasterResearch 3 78 - 88 2008年02月 [査読有り][通常論文]
  • KAWASHIMA M.
    J. Atmos. Sci. 64 7 2355 - 2377 2007年07月01日 [査読有り]
     
    Abstract The mechanism responsible for the core-gap structure of precipitation along narrow cold-frontal rainbands (NCFRs) is investigated through analyses of idealized cloud-resolving simulations of cold fronts. The control simulation, in which the prefrontal thermal stratification is characterized by a weak convective instability at low levels with convective available potential energy (CAPE) of ∼60 J kg−1, reproduces the typical alongfront variability of observed NCFRs. The simulated NCFR is broken up into regularly spaced, ellipsoidal cores oriented at a clockwise angle to the cold front. While horizontal-shear instability (HSI) has frequently been proposed as a mechanism leading to the alongfront variability of NCFRs, no characteristic features of HSI are recognized in the simulated vertical vorticity field at the leading edge of the cold front. The alongfront variability in precipitation is attributed to the formation of a wavelike disturbance just above the leading edge of the cold front. The wave phase lines are oriented nearly perpendicular to the direction of mean vertical shear, with enhanced (suppressed) precipitation occurring at the wave updrafts (downdrafts). An analysis of the eddy kinetic energy budget indicates that the wavelike disturbance derives most of its energy from the mean vertical shear and the buoyancy. Sensitivity experiments reveal a systematic relationship between the alongfront variability of NCFRs and the stability of the prefrontal thermal stratification. Simulated precipitation cores remain essentially parallel to the cold front when the prefrontal environment is absolutely stable or almost neutral to surface parcel ascent. The typical alongfront variability of NCFRs is reproduced for weakly unstable environments with small amounts of CAPE (≤140 J kg−1). On the other hand, simulations with sufficiently unstable environments produce precipitation cores oriented counterclockwise to cold fronts.
  • Zhuxiao Li, Takao Takeda, Kazuhisa Tsuboki, Kuranoshin Kato, Masayuki Kawashima, Yasushi Fujiyoshi
    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN 85 1 25 - 45 2007年02月 [査読有り][通常論文]
     
    Global Water Cycle Experiment (GEWEX)-Asian Monsoon Experiment (GAME)/Huaihe River Basin Energy Water Cycle Experiments (GAME/HUBEX) were conducted during the Meiyu period in 1998 and 1999. Using infrared brightness temperature (T-BB) data of the Geostationary Meteorological Satellite (GMS)-5, we investigated the diurnal variation of 61 long-lasting cloud clusters that developed during GAME/HUBEX Intensive Observation Periods (IOPs). More than two-thirds of the cloud clusters, named nocturnal-type clusters, attained a convective peak between midnight and early morning, with most peaking between 00 and 02 LST. Almost all of these nocturnal-type cloud clusters developed in, or south of the Meiyu frontal zone. The other clusters, named evening-type cloud clusters, peaked from late afternoon to evening, and were less intense than the nocturnal clusters.
  • Findy Renggono, Masayuki K. Yamamoto, Hiroyuki Hashiguchi, Shoichiro Fukao, Toyoshi Shimomai, Masayuki Kawashima, Mahally Kudsy
    RADIO SCIENCE 41 5 2006年09月 [査読有り][通常論文]
     
    [ 1] The diurnal variability of raindrop size distribution (DSD) in precipitating clouds over Kototabang, West Sumatra, Indonesia (0.20 degrees S, 100.32 degrees E), is studied using three types of Doppler radars, operated at VHF ( 47 MHz), UHF (1.3 GHz), and X band (9.4 GHz) frequencies. Two precipitation events from 5 to 6 May 2004 in the first observation campaign of the first Coupling Processes in the Equatorial Atmosphere (CPEA-I) project reveal a difference between clouds precipitating in the early afternoon and clouds precipitating in the nighttime. In the early afternoon, the precipitating clouds were dominated by shallow convective types with high rainfall rate at the surface. In the nighttime, precipitating clouds were dominated by stratiform types with small rainfall rate at the surface. A diurnal variation of horizontal wind was observed over this area. The westerly in the lower troposphere and the easterly in the middle troposphere began to be enhanced in the afternoon ( 1400 - 1700 LT). DSD parameters were retrieved from VHF band Doppler radar data. A modified gamma distribution was used to model DSD parameters. The shape parameter ( m) was larger during stratiform precipitation than during shallow convective precipitation events, as shown by previous studies. During stratiform rain events on 5 May 2004, the median volume diameter (D-0) was dominantly greater than 1 mm, which is larger than D-0 during shallow convective rain events. Results presented in this paper indicate that DSD has a diurnal cycle over the mountainous region of Sumatra.
  • Simon Alexander, Toshitaka Tsuda, Jun-ichi Furumoto, Toyoshi Shimomai, Toshiaki Kozu, Masayuki Kawashima
    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN 84A 57 - 93 2006年07月 [査読有り][通常論文]
     
    Data from the Equatorial Atmosphere Radar (EAR) were analysed during the Coupling Processes in the Equatorial Atmosphere (CPEA) campaign of April-May 2004. Statistical averages of the daily perturbations of wind velocity, temperature and humidity were examined. In the lower stratosphere, horizontal wind variances of up to 1.5 m(2)s(-2) were visible above the afternoon tropospheric convection. Vertical wind variances of up to 0.03 m(2)s(-2) occurred at the same time. The average variances of temperature and humidity in the lower troposphere also increased in the afternoon. Estimates of average momentum flux were made. In the lower stratosphere (18.0-20.0 km), the average magnitudes were 0.7-0.9 m(2)s(-2) for both vertical bar mu'w'vertical bar and vertical bar upsilon'w'vertical bar. These fluxes were observed above the convective cells and indicate the average momentum emitted by them. Residuals of the momentum flux components showed a small westward preference and very small northward directional preference for wave propagation during CPEA. Four individual convective events and three Super Cloud Clusters (SCCs) were examined in detail. Tropospheric horizontal and vertical wind variances increased by 5 to 10 times during intense convection. Directly above this convection, in the lower stratosphere, increases in variance were also recorded. Vertical wind velocity fluctuation amplitudes in the lower stratosphere increased from 0.05-0.1 ms(-1) away from convection, to be 0.1-0.4 ms(-1) during convection. The amplitudes decreased to their background levels as soon as the convection had passed the EAR site. In the lower troposphere, the virtual temperature perturbations increased to 1.0-2.0 degrees C during convection, an increase from a background value of about 0.5 degrees C. During two of the four individual events, the amplitude of the temperature perturbations stayed enhanced for several hours after the end of convection. This contrasts with the vertical velocities in the lower troposphere, which quickly decreased following the passage of the storms. Specific humidity profiles in most cases showed large increases in the amount of water vapour below 4 km during times of convection. At certain heights and times during intense convection, the specific humidity increased by up to 50% from its background level.
  • Shuichi Mori, Jun-Ichi Hamada, Manabu D. Yamanaka, Yasu-Masa Kodama, Masayuki Kawashima, Toyoshi Shimomai, Yoshiaki Shibagaki, Hiroyuki Hashiguchi, Tien Sribeviawati
    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN 84A 113 - 131 2006年07月 [査読有り][通常論文]
     
    Characteristics of vertical wind profiles (VWPs) in precipitating clouds were studied over western Sumatera (or Sumatra) Island of the Indonesian maritime continent during the first Coupling Process of Equatorial Atmosphere (CPEA) campaign period (10 April-09 May 2004) using Equatorial Atmosphere Radar (EAR) and X-band Doppler radar (XDR) to examine the dynamic and thermodynamic structures of various types of tropical precipitating systems. VWPs were precisely measured with the EAR directly in precipitating clouds, which were identified using simultaneous XDR observation. A super-cloud cluster (SCC) system of the intraseasonal variation (ISV) onset phase was examined as a case study. The SCC consisted of three cloud clusters (CCs), which were further partitioned into convective and stratiform cloud regions based on the XDR reflectivity fields. Vertical winds varied greatly in time and height according to variations in the reflectivity fields. Although the VWPs for each CC showed quite scattered variations in time and height, they had significant dependence on the corresponding 10 dBZ radar echo top heights (H(10dBZ)s). Spectral representations of vertical wind and reflectivity profiles, which were stratified by H-10dBZ heights, showed the following distinct characteristics: 1) Convective spectra were divided into two groups by H-10dBZ = 10 km. The shorter spectra had massive reflectivity, especially in the lower height with upward currents; the taller spectra had a gentle reflectivity profile with significant upward currents around H-10dBZ and apparent downward currents below 8 km in height. 2) Spectra for stratiform clouds were partitioned into three groups by H-10dBZ = 6 and 8 km. Beside the shortest group of shallow stratiform clouds, bright band signs were intensified as the H-10dBZ increased in the taller two groups. The heights of the maximum upward currents above their bright bands also increased too with the heights of H-10dBZ. The reflectivity spectra and VWPs are discussed in comparison to global precipitation spectra observed by the Tropical Rainfall Measuring Mission (TRMM) satellite and VWPs calculated by rawinsonde sounding array data, respectively.
  • KAWASHIMA Masayuki, FUJIYOSHI Yasushi, OHI Masayuki, HONDA Tetsuya, KOZU Toshiaki, SHIMOMAI Toyoshi, HASHIGUCHI Hiroyuki
    気象集誌. 第2輯 84A 33 - 56 Meteorological Society of Japan 2006年 [査読有り]
     
    During the latter half of the first CPEA campaign (CPEA-I), X-band Doppler radar (XDR) observation was carried out from 10 April to 9 May 2004 in west Sumatera. In this paper, characteristics of precipitating systems and their relation to the Madden-Julian Oscillation (MJO) are investigated based on the analysis of the XDR data.
    Significant diurnal variations of precipitation were observed both in the convectively inactive and active phases of MJO, in which the area of intense echoes with reflectivity greater than 40 dBZ attained a maximum around 16 LST, whereas the area of weaker echoes attained a maximum in the evening. However, while the area of weaker echoes showed significant drop in the evening (21 LST) in the inactive phase, such a drop occurred in the early morning in the active phase. During the convectively inactive phase from 10 to 22 April, the precipitation was caused by systems that formed within the observation area. Shallow convective cells appeared in the mountain range around midday, which subsequently developed into deep convective systems. These convective systems then migrated southwestward in many cases, but in some cases they were observed to split and then migrated both southwestward and northeastward. During the convectively active phase from 23 April to 6 May, much of the precipitation occurred associated with the development of pre-existing cloud systems within super cloud clusters (SCCs). While the precipitation area with weak to moderate reflectivity became considerably larger than that in the convectively inactive phase, the area and the top heights of intense echoes were generally suppressed. Environmental factors responsible for these modulations in precipitation are also discussed.
    The structure and evolution of precipitation systems were further investigated for some selected cases. The precipitation system observed on 17 April showed typical evolution during the convectively inactive phase, whereas the precipitation system on 11 Apri1 was observed to split into two systems that migrated southwestward and northeastward. The northeastward migrations of the precipitation systems occurred as a result of successive generation of new convective elements on the northeastern side of old ones. The precipitation systems observed on 23-24 April and 5-6 May occurred during passages of SCCs, and moved eastward associated with intrusions of low-level westerlies. These systems were composed of convective regions around the leading portions of the low-level westerlies, and stratiform regions behind. Analyses of reflectivity and Doppler velocity fields for the latter case suggested that the elevated orography in the west Sumatera temporarily blocked the eastward propagation of the system and the intrusion of the low-level westerly.
  • Inoue, J, M. Kawashima, Y. Fujiyoshi, M.Wakatsuchi
    Journal of theMeteorologicalSociety ofJapan 83 2 189 - 200 2005年05月 [査読有り][通常論文]
     
    Russian research aircraft observed the atmospheric boundary layer in 2001 during weak (29 Jan.), intense (2 Feb.), and very intense (3 Feb.) cold air outbreaks. These observations occurred during a field experiment of Winter Meso-scale convective systems Observations, over the Sea of Japan in 2001 (WMO-01). Conditional sampling techniques were used to elucidate air-mass modification processes upstream of the Sea of Japan during cold-air outbreaks. Buoyancy fluxes in the lower boundary layer near the sea surface differed significantly among the three cases. TKE budgets suggest that the differences were characterized mainly by differences in buoyancy production. However, common properties in heat transfer did exist, namely intensity (3.0) and fractional coverage (28%) of rising thermals (w+Tu +). Scale analysis showed that heating by convective-scale motions dominated in the lower boundary layer. Heating by meso-γ scale motions became more important in the upper boundary layer. Near the cloud top, on the other hand, contributions by cold downdrafts (w-Tu -) to the total buoyancy flux (w'Tu') dominated. The cloud-top w'T'u was about half of that near the sea surface, suggesting that cooling processes near the cloud top are also important in TKE production. Comparisons of fractional spatial coverage of w̄+Tu + with thermal motions over other warm oceans show good agreement with the AMTEX and GALE cases. However, flux intensities in the present case, and in the GALE case, are stronger than in the AMTEX case. Impacts on ocean convection by the upstream, large surface heat fluxes are discussed. © 2005, Meteorological Society of Japan.
  • YOSHIHARA Hanako, KAWASHIMA Masayuki, ARAI Ken-ichiro, INOUE Jun, FUJIYOSHI Yasushi
    気象集誌. 第2輯 82 4 1057 - 1079 公益社団法人 日本気象学会 2004年 [査読有り]
     
    During the field experiment of winter mesoscale convective systems over the Sea of Japan in 2001 (WMO-01), several snowbands associated with a cold front developed remarkably at 10∼30 km off the coast of Hokuriku district on 28 and 29 January 2001. Dual-Doppler radar analysis was made to investigate the mechanisms responsible for the successive development of the snowbands. Derived wind fields revealed that a mesoscale convergence line was formed between the prevailing westerly and shallow (∼1 km depth), cold southwesterly winds that blew from inland toward Toyama bay. As the downshear-tilting convective cells in the snowbands approached the convergence line, they became almost upright and their height increased from 4 km to 6∼7 km. The edge of the southwesterly cold air temporarily became indistinct because of the entrainment of the air into the convective cells that developed aloft. However, the subsequent advection of the cold southwesterly reestablished the convergence line, and enabled the successive development of following snowbands.
  • T Ushiyama, M Kawashima, Y Fujiyoshi
    JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN 81 6 1407 - 1434 2003年12月 [査読有り][通常論文]
     
    Dual Doppler radar observations were carried out from November 1992 to January 1993 during the TOGA-COARE IOP (Tropical Ocean and Global Atmosphere-Coupled Ocean Atmosphere Response Experiment, Intensive Observation Phase) at Manus Island in Papua New Guinea. The heating profiles of six stratiform and eight convective cloud systems were calculated using three-dimensional wind field and hydrometeor distribution in a same way as Roux and Sun (1990). Relations between the heating profiles and the thermodynamic properties of environment were studied. Convective and stratiform cloud systems both showed structures consistent with past studies. The heating level varied significantly with environmental conditions that had been linked to the phase of Madden Julian Oscillation (MJO). Specifically, at the beginning of the active phase of MJO, convective cloud systems dominated and the heating level was high (7 km). These cloud systems heated and moistened the middle to upper troposphere and stabilized the atmosphere. In the middle of the active phase of MJO, stratiform cloud systems dominated and the heating level lowered (5 km). At the end of the active phase of the MJO, convective cloud systems again dominated. A composite profile for the entire observation period was calculated using the representative profiles and satellite data, and was compared with that derived by Lin and Johnson (1996) using radiosonde observation. The derived maximum heating rate coincided with their results, however, the heating rates of lower and upper troposphere were smaller and the level of maximum heating (5 km) was slightly lower.
  • KAWASHIMA Masayuki
    気象集誌. 第2輯 81 4 713 - 746 Meteorological Society of Japan 2003年 [査読有り]
     
    Observed or simulated mesoscale convective systems (MCSs) often show pulsations with time periods of a few hours. In this paper, results from a two-dimensional cloud model are used to determine the dynamical processes responsible for such self-modulating oscillations (meso-β-scale cycle, MBC) in squallline type convective systems. The simulated storms have weak cold pools and include notable pulsations with time periods of 3∼4 hours. These pulsations are manifested as periodic organizations of convective-scale cells into upsheartilted meso-β-scale cells (MCs). A rearward-propagating, dissipating MC and disturbances on the downshear side have the properties of vertically propagating gravity waves, with storm-relative time periods that are about 1.5 hour less than those of the MBC. Dry model simulations driven by prescribed thermal forcings show that the waves arise in response to the reduction of latent heating in the MC in its stationary stage.
    The evolution of storm structure following a convective burst is related to the phasing of the uppertropospheric wave disturbances relative to the lower-tropospheric disturbances. The storm exhibits multicellular structure so long as the downward and frontward acceleration phase of gravity waves exerts suppressing effects on convections behind the gust front. As the phase propagates to the rear, it in turn enhances the convergence at the terminus of the steady lower-tropospheric front-to-rear flow, aiding the cell reinvigoration there. The time period of MBC increases as MCs tilt more horizontally in their stationary growth stage, and as the storm-relative rear-to-front upper-tropospheric wind increases. The former effect increases the intrinsic period of excited waves, and the latter increases the storm-relative period of the waves by Doppler-shifting the phase speed. These results support the argument that gravity waves generated by tilted MCs are prominent in the dynamics of MBCs.
  • J Inoue, M Kawashima, Y Fujiyoshi, M Yoshizaki
    15TH SYMPOSIUM ON BOUNDARY LAYERS AND TURBULENCE 53 - 54 2002年 [査読有り][通常論文]
  • J Inoue, M Kawashima, Y Fujiyoshi, M Wakatsuchi
    15TH SYMPOSIUM ON BOUNDARY LAYERS AND TURBULENCE 102 - 103 2002年 [査読有り][通常論文]
  • Inoue Jun, Honda Meiji, Kawashima Masayuki
    気象集誌. 第2輯 79 2 657 - 670 Meteorological Society of Japan 2001年 [査読有り]
     
    Radio sounding and in-situ observations at land-based (26 January-11 February 1998) and ship stations (4-11 February 1998) were performed over the southwestern Sea of Okhotsk covered with sea ice to estimate turbulent heat flux and investigate characteristics of thermodynamic air mass transformation processes during cold-air outbreaks. Surface heat flux estimations were carried out using two indirect methods; an atmospheric heat budget analysis using the radio sounding data at three stations and a bulk method utilizing meteorological and sea ice thickness data obtained by the ship observations. The estimated total upward turbulent heat flux over the analyzed area was approximately 100 Wm-2 even within the intense cold-air outbreak period. The height of the mixing layer associated with this small amount of the heat flux is only about 1 km, which implies that sea ice acts as an insulating material between the ocean and atmosphere and thus significantly reduces the turbulent heat fluxes. Nevertheless, the upward turbulent heat flux from the ice surface was found to be non-negligible during cold-air outbreaks and it is suggested that the sea ice grows through the sea or ice surface cooling.
  • JL Redelsperger, PRA Brown, F Guichard, C Hoff, M Kawashima, S Lang, T Montmerle, K Nakamura, K Saito, C Seman, WK Tao, LJ Donner
    QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 126 564 823 - 863 2000年04月 [査読有り][通常論文]
     
    Results from eight cloud-resolving models are compared for the first time for the case of an oceanic tropicalsquall line observed during the Tropical Ocean/Global Atmosphere Coupled Ocean-Atmosphere Response Experiment. There is broad agreement between all the models in describing the overall structure and propagation of the squall line and some quantitative agreement in the evolution of rainfall. There is also a more qualitative agreement between the models in describing the vertical structure of the apparent heat and moisture sources. The three-dimensional (3D) experiments with an active ice phase and open lateral boundary conditions along the direction of the system propagation show good agreement for all parameters. The comparison of 3D simulated fields with those obtained from two different analyses of airborne Doppler radar data indicates that the 3D models are able to simulate the dynamical structure of the squall line, including the observed double-peaked updraughts. However, the second updraught peak at around 10 km in height is obtained only when the ice phase is represented. The 2D simulations with an ice-phase parametrization also exhibit this structure, although with a larger temporal variability. In the 3D simulations, the evolution of the mean wind profile is in the sense of decreasing the shear, but the 2D simulations are unable to reproduce this behaviour.
  • Jun Inoue, Masayuki Kawashima, Kay I. Ohshima, Yasushi Fujiyoshi, Ken-Ichi Maruyama
    Journal of Oceanography 56 5 507 - 515 2000年 [査読有り][通常論文]
     
    Horizontal wind fields over Funka Bay during cold air outbreaks were simulated using a 3-D meso-scale atmospheric model. The simulated wind fields over the bay have a positive curl in the north and a negative curl in the south. These wind fields were used to simulate the current in Funka Bay using a barotropic ocean model. The simulated current pattern was composed of two vortices-one with anti-clockwise vorticity in the north and the other with clockwise vorticity in the south-and was in the opposite direction to that simulated by the uniform wind fields. This is because the wind stress curl effect on the vorticity production in Funka Bay opposes and overwhelms the bathymetry torque effect during cold air outbreaks. These results show that the non-uniformity of the wind fields caused by the land topography around a shallow lake or bay cannot be neglected in simulating its currents.
  • Masayuki Kawashima, Kazuhisa Tsuboki, Tomio Asai
    Journal of the Meteorological Society of Japan. Ser. II 73 3 717 - 735 1995年 [査読有り]
  • Taku Tada, Yoshinobu Tsuji, Masahito Tsukamoto, Yoshikazu Ueno, Masayuki Kawashima, Takashi Egawa, Yasuhiro Yamazaki
    Pure and Applied Geophysics PAGEOPH 138 2 309 - 322 1992年 [査読有り]

書籍

  • 低温科学便覧
    北海道大学低温科学研究所編 (担当:分担執筆範囲:第12.3章,12.4 章 雲科学〜メソスケール渦状降雪雲の力学，温帯低気圧に伴う降雨帯形成に果たす雪の融解冷却効果)
    2015年10月
  • 地球惑星科学入門
    在田一則, 竹下徹, 見延庄士郎, 渡部重十編集 (担当:分担執筆範囲:第22章 天気を支配する諸現象)
    北海道大学出版会 2010年11月

その他活動・業績

共同研究・競争的資金等の研究課題

  • メソスケール降水システムに関する研究
  • study on meso-scale precipitating systems

教育活動情報

主要な担当授業

  • 気候ﾓﾃﾞﾘﾝｸﾞ特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 数値モデリング、気候、大気、海洋 Numerical modeling, Climate, Atmosphere, Ocean
  • 大気環境科学特論
    開講年度 : 2021年
    課程区分 : 修士課程
    開講学部 : 環境科学院
    キーワード : 空間スケール, 総観規模, メソ, ローカル, 大気汚染, 境界層, 乱流, 熱収支, 炭素収支, 雲物理, 雨, 雪, 降水過程, パラメタリゼーション, エアロゾル spatial scale, synoptic, meso, local, air pollution, boundary layer, turbulence, heat budget, carbon budget, cloud physics, rain, snow, precipitation, parameterization, aerosol

大学運営

委員歴

  • 2008年09月 - 現在   日本気象学会   気象集誌編集委員
  • 2000年09月 - 現在   日本気象学会   「天気」編集委員

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