著者
Kentaro Araki Teruyuki Kato Yasutaka Hirockawa Wataru Mashiko
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
pp.2021-002, (Released:2020-12-24)
被引用文献数
5

This study investigated characteristics of atmospheric environmental fields in the occurrence of quasi-stationary convective bands (QSCBs) in Kyushu, western Japan during the July 2020 heavy rainfall event. We performed case studies of extreme rainfall subevents in the Kumamoto and Kagoshima prefectures on 3-4 July (2020KK) and northern Kyushu on 6-7 July 2020 (2020NK), compared with two heavy rainfall events in northern Kyushu in 2017 and 2018.Nine QSCBs were objectively extracted during the July 2020 heavy rainfall event, causing hourly precipitation amounts exceeding 100 mm twenty times. In 2020KK, the environmental field with extremely large precipitable water due to low-level and middle-level humidity was affected by the upper-level cold airflow, which resulted in favorable condition for the deep convection development. Consequently, the lightning activity became high, and cloud tops were the highest in comparison to previous events. QSCBs in 2020KK and 2020NK were located along a low-level convergence line/zone associated with an inflow that had extremely large water vapor flux on the south side of the mesoscale Baiu frontal depressions. In most of the QSCB cases in 2020, mesoscale depressions were observed and enhanced horizontal winds, which led to extremely large low-level water vapor flux to produce short-term heavy rainfall.
著者
Yukiko Imada Masahiro Watanabe Hiroaki Kawase Hideo Shiogama Miki Arai
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.15A, pp.8-12, 2019 (Released:2019-06-07)
参考文献数
16
被引用文献数
13 34

The high temperature event in July 2018 caused record-breaking human damage throughout Japan. Large-ensemble historical simulations with a high-resolution atmospheric general circulation model showed that the occurrence rate of this event under the condition of external forcings in July 2018 was approximately 20%. This high probability was a result of the high-pressure systems both in the upper and lower troposphere in July 2018. The event attribution approach based on the large-ensemble simulations with and without human-induced climate change indicated the following: (1) The event would never have happened without anthropogenic global warming. (2) The strength of the two-tiered high-pressure systems was also at an extreme level and at least doubled the level of event probability, which was independent of global warming. Moreover, a set of the large-ensemble dynamically downscaled outputs revealed that the mean annual occurrence of extremely hot days in Japan will be expected to increase by 1.8 times under a global warming level of 2°C above pre-industrial levels.
著者
Naveen CHANDRA Prabir K. PATRA Jagat S. H. BISHT 伊藤 昭彦 梅澤 拓 三枝 信子 森本 真司 青木 周司 Greet JANSSENS-MAENHOUT 藤田 遼 滝川 雅之 渡辺 真吾 齋藤 尚子 Josep G. CANADELL
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
vol.99, no.2, pp.309-337, 2021 (Released:2021-04-15)
参考文献数
92
被引用文献数
6 6

メタン(CH4)は主要な温室効果気体の一つであり、対流圏および成層圏における化学過程にも重要な役割を果たしている。気候変動および大気汚染に関するCH4の影響は非常に大きいが、過去30年間のCH4濃度増加率や経年変動の要因については、未だ科学的な確証が得られていない。本研究は、十分に検証された化学輸送モデルを用いて、1988年から2016年の期間を対象に大気中CH4濃度をシミュレートし、逆解析によって地域別CH4排出量を推定した。まず、標準実験としてOHラジカルの季節変動のみを考慮し、大気中CH4濃度の観測データを用いた逆解法モデル、排出インベントリ、湿地モデル、およびδ13C-CH4のボックスモデルを用いた解析を行ったところ、1988年以降におけるヨーロッパとロシアでのCH4排出量の減少が示された。特に、石油・天然ガス採掘と畜産由来の排出量の減少が1990年代のCH4増加率の減少に寄与していることが明らかとなった。その後、2000年代初頭には大気中CH4濃度が準定常状態になった。 2007年からはCH4濃度は再び増加に転じたが、これは主に中国の炭鉱からの排出量の増加と熱帯域での畜産の拡大によるものと推定された。OHラジカルの年々変動を考慮した感度実験を行ったところ、逆解析による中高緯度域からのCH4排出推定量はOHラジカルの年々変動には影響されないことが示された。さらに,我々は全球的なCH4排出量が低緯度側へシフトしたことと熱帯域でのOHラジカルによるCH4消失の増加が相殺したことによって、南半球熱帯域と北半球高緯度域の間のCH4濃度の勾配は1988-2016年の間にわたってほとんど変化していなかったことを明らかにした。このような排出地域の南北方向のシフトは、衛星によるCH4カラム観測の全球分布からも確認された。今回の解析期間には、北極域を含めて地球温暖化によるCH4排出量の増加は確認できなかった。これらの解析結果は、気候変動の緩和へ向けた効果的な排出削減策を行う上で重要な排出部門を特定することに貢献できると思われる。
著者
Seiji YUKIMOTO Yukimasa ADACHI Masahiro HOSAKA Tomonori SAKAMI Hiromasa YOSHIMURA Mikitoshi HIRABARA Taichu Y. TANAKA Eiki SHINDO Hiroyuki TSUJINO Makoto DEUSHI Ryo MIZUTA Shoukichi YABU Atsushi OBATA Hideyuki NAKANO Tsuyoshi KOSHIRO Tomoaki OSE Akio KITOH
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
vol.90A, pp.23-64, 2012 (Released:2012-06-07)
参考文献数
157
被引用文献数
354 496

A new global climate model, MRI-CGCM3, has been developed at the Meteorological Research Institute (MRI). This model is an overall upgrade of MRI’s former climate model MRI-CGCM2 series. MRI-CGCM3 is composed of atmosphere-land, aerosol, and ocean-ice models, and is a subset of the MRI’s earth system model MRI-ESM1. Atmospheric component MRI-AGCM3 is interactively coupled with aerosol model to represent direct and indirect effects of aerosols with a new cloud microphysics scheme. Basic experiments for pre-industrial control, historical and climate sensitivity are performed with MRI-CGCM3. In the pre-industrial control experiment, the model exhibits very stable behavior without climatic drifts, at least in the radiation budget, the temperature near the surface and the major indices of ocean circulations. The sea surface temperature (SST) drift is sufficiently small, while there is a 1 W m-2 heating imbalance at the surface. The model’s climate sensitivity is estimated to be 2.11 K with Gregory’s method. The transient climate response (TCR) to 1 % yr-1 increase of carbon dioxide (CO2) concentration is 1.6 K with doubling of CO2 concentration and 4.1 K with quadrupling of CO2 concentration. The simulated present-day mean climate in the historical experiment is evaluated by comparison with observations, including reanalysis. The model reproduces the overall mean climate, including seasonal variation in various aspects in the atmosphere and the oceans. Variability in the simulated climate is also evaluated and is found to be realistic, including El Niño and Southern Oscillation and the Arctic and Antarctic oscillations. However, some important issues are identified. The simulated SST indicates generally cold bias in the Northern Hemisphere (NH) and warm bias in the Southern Hemisphere (SH), and the simulated sea ice expands excessively in the North Atlantic in winter. A double ITCZ also appears in the tropical Pacific, particularly in the austral summer.
著者
Kosuke Ito Hiroyuki Yamada Munehiko Yamaguchi Tetsuo Nakazawa Norio Nagahama Kensaku Shimizu Tadayasu Ohigashi Taro Shinoda Kazuhisa Tsuboki
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.14, pp.105-110, 2018 (Released:2018-07-28)
参考文献数
30
被引用文献数
1 14

The inner core of Tropical Cyclone Lan was observed on 21-22 October 2017 by GPS dropsondes during the first aircraft missions of the Tropical Cyclones-Pacific Asian Research Campaign for the Improvement of Intensity Estimations/Forecasts (T-PARCII). To evaluate the impact of dropsondes on forecast skill, 12 36-h forecasts were conducted using a Japan Meteorological Agency non-hydrostatic model (JMA-NHM) with a JMA-NHM-based mesoscale four-dimensional data assimilation (DA) system. Track forecast skill improved over all forecast times with the assimilation of the dropsonde data. The improvement rate was 8-16% for 27-36-h forecasts. Minimum sea level pressure (Pmin) forecasts were generally degenerated (improved) for relatively short-term (long-term) forecasts by adding the dropsonde data, and maximum wind speed (Vmax) forecasts were degenerated. Some of the changes in the track and Vmax forecasts were statistically significant at the 95% confidence level. It is notable that the dropsonde-derived estimate of Pmin was closer to the real-time analysis by the Regional Specialized Meteorological Center (RSMC) Tokyo than the RSMC Tokyo best track analysis. The degeneration in intensity forecast skill due to uncertainties in the best track data is discussed.
著者
Kosuke Ito
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.12, pp.247-252, 2016 (Released:2016-09-16)
参考文献数
18
被引用文献数
14 15

Tropical cyclone (TC) intensity forecasts issued by the Regional Specialized Meteorological Centre (RSMC) Tokyo - Typhoon Center are systematically compiled to analyze the long-term behavior of errors and to explore the potential for improvement in the forecast accuracy using a statistical correction approach. In this study, a dataset is constructed from annual statistics and every single forecast listed on annual reports on the activities of the RSMC Tokyo. This study found that (1) the accuracy of annual mean forecast has not improved over 26 years and that (2) forecast errors tend to be larger in the rapidly developing TCs. Further analysis reveals that recent forecast output (2008-2014) contains biases associated with the magnitude of the vertical shear of horizontal wind, convective available potential energy, upper ocean temperature, maximum potential intensity (MPI) and ocean coupling potential intensity (OC_PI). To evaluate the adverse effect of such biases in the current forecast system, a simple statistical correction is applied. It improved TC intensity forecast by 7.8-16.9% when an OC_PI is employed.
著者
YAMAGUCHI Munehiko MAEDA Shuhei
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
pp.2020-039, (Released:2020-05-21)
被引用文献数
3

Based on observations, the number of tropical cyclones (TCs) approaching the southern coast of Japan, including Tokyo, has increased over the last 40 years, and these TCs are increasing in strength when they approach land. The environmental conditions for TC development have become more favorable, with warmer sea surface temperature, less vertical wind shear and more moisture in the atmosphere. In addition, the translation speed of TCs has decreased, which indicates a longer influence time. Comparison of the synoptic environment during July–October between the first (1980-1999, P1) and second (2000-2019, P2) 20 years shows that the sub-tropical high is strengthened in P2, where the western and northern edge of the high extends further the west and the north, respectively. Also, the westerly jet is weakened in P2 over and south of Japan in the middle to upper troposphere. These changes in the synoptic environment are considered to play a role in increasing the number of TCs approaching Tokyo and also in producing more favorable conditions for TC development. The relationship between the changes in TC characteristics over the last 40 years and global warming is unclear. As the Pacific Decadal Oscillation (PDO) is in a positive phase in P1 and a negative phase in many years of the P2 period, decadal oscillations may have played some role in the increase in the number of approaching TCs and in the changes in the synoptic environment.
著者
Yukiko Imada Masahiro Watanabe Hiroaki Kawase Hideo Shiogama Miki Arai
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
pp.15A-002, (Released:2019-05-22)
被引用文献数
12 34

The high temperature event in July 2018 caused record-breaking human damage throughout Japan. Large-ensemble historical simulations with a high-resolution atmospheric general circulation model showed that the occurrence rate of this event under the condition of external forcings in July 2018 was approximately 20%. This high probability was a result of the high-pressure systems both in the upper and lower troposphere in July 2018. The event attribution approach based on the large-ensemble simulations with and without human-induced climate change indicated the following: (1) The event would never have happened without anthropogenic global warming. (2) The strength of the two-tiered high-pressure systems was also at an extreme level and at least doubled the level of event probability, which was independent of global warming. Moreover, a set of the large-ensemble dynamically downscaled outputs revealed that the mean annual occurrence of extremely hot days in Japan will be expected to increase by 1.8 times under a global warming level of 2°C above pre-industrial levels.
著者
村松 照男
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
vol.64, no.2, pp.259-272, 1986 (Released:2007-10-19)
参考文献数
17
被引用文献数
13 14

レーダーと衛星で決定した台風眼(T8019, WYNNE)の移動軌跡上にトロコイダル運動による顕著な周期変動が観測された。周期は5~8時間,最大振幅は23kmであった。周期の減少とともに振幅も減少した。レーダーエコーの解析の結果,台風眼の中心は台風系全体の中心とは一致せず,約20km偏位し系の中心に対し反時計回りに回転していることが明らかとなった。この間,外側と内側の eye wal1の直径が各々260kmと30kmである二重眼構造と,それに対応する風速分布の二重極大が観測された。特に,気圧と風速場で楕円状の循環が見られ,その結果としての矩形状エコー構造が外側 eye wal1の内側で観測された。この矩形と楕円状循環は台風系の中心に対しトロコイダル周期と同周期で,外側 eye wal1に内接しながら回転していた。台風眼は楕円の一方の焦点を追うように移動し,この結果としてトロコイダル軌跡となった。しかしながら,なぜ眼が系の中心から偏れるのかはまだ明らかとなっていない。
著者
ITO Kosuke WU Chun-Chieh CHAN Kelvin T. F. TOUMI Ralf DAVIS Chris
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
pp.2020-001, (Released:2019-10-08)
被引用文献数
4

While the fundamental understanding of the movement of a tropical cyclone (TC) is fairly mature, there are still notable advancements being made. This paper summarizes new concepts and updates on existing fundamental theories on TC movement obtained from simplified barotropic models, full-physics models, and data analysis particularly since 2014. It includes the recent works on the interaction of the TC with its environment and the fundamental aspects of predictability related to TC movement. The conventional concepts of the steering flow, β-gyre, and diabatic heating remain important. Yet, a more complete understanding of mechanisms governing TC movement serves as an important basis toward the further improvement of track forecasts.
著者
Shion Sekizawa Takafumi Miyasaka Hisashi Nakamura Akihiko Shimpo Kazuto Takemura Shuhei Maeda
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
pp.15A-005, (Released:2019-05-22)
被引用文献数
19

During a torrential rainfall event in early July 2018, profound enhancement of moisture influx from the south and its convergence occurred over western Japan, which is investigated in this study on the basis of objective analysis and forecast data from the Japan Meteorological Agency Meso-Scale Model. The heavy rainfall over western Japan is found to accompany enhanced oceanic evaporation extensively around Japan, especially around the Kuroshio and entirely over the Sea of Japan. Linear decompositions of the anomalous moisture flux and surface latent heat flux anomalies applied to the high-resolution data reveals that the intensified speed of the low-level southerlies was the primary factor for the pronounced enhancement of both the moisture transport into the heavy rainfall region, especially in its western portion, and evaporation around the Kuroshio into the southerlies. An additional contribution is found from positive sea-surface temperature anomalies to the enhanced southerly moisture inflow into the eastern portion of the rainfall region. These findings have been confirmed through a backward trajectory analysis, which suggests that anomalous moisture supply to air parcels into the rainfall region primarily through the enhanced wind-forced evaporation roughly corresponds to about 10% of the precipitable water anomaly over western Japan.
著者
CHANDRA Naveen PATRA Prabir K. BISHT Jagat S. H. ITO Akihiko UMEZAWA Taku SAIGUSA Nobuko MORIMOTO Shinji AOKI Shuji JANSSENS-MAENHOUT Greet FUJITA Ryo TAKIGAWA Masayuki WATANABE Shingo SAITOH Naoko CANADELL Josep G.
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
pp.2021-015, (Released:2020-12-04)
被引用文献数
6

Methane (CH4) is an important greenhouse gas and plays a significant role in tropospheric and stratospheric chemistry. Despite the relevance of methane (CH4) in human-induced climate change and air pollution chemistry, there is no scientific consensus on the causes of changes in its growth rates and variability over the past three decades. We use a well-validated chemistry-transport model for simulating CH4 concentration and estimation of regional CH4 emissions by inverse modelling for the period of 1988-2016. The control simulations are performed using a seasonally varying hydroxyl (OH) concentrations and assumed no interannual variability. Using inverse modelling of atmospheric observations, emission inventories, a wetland model, and a δ13C-CH4 box model, we show that reductions in emissions from Europe and Russia since 1988, particularly from oil-gas exploitation and enteric fermentation, led to decreased CH4 growth rates in the 1990s. This period was followed by a quasi-stationary state of CH4 in the atmosphere during the early 2000s. CH4 resumed growth from 2007, which we attribute to increases in emissions from coal mining mainly in China and intensification of ruminant farming in tropical regions. A sensitivity simulation using interannually varying OH shows that regional emission estimates by inversion are unaffected for the mid- and high latitude areas. We show that meridional shift in CH4 emissions toward the lower latitudes and the increase in CH4 loss by hydroxyl (OH) over the tropics finely balance out, which keep the CH4 gradients between the southern hemispheric tropical and polar sites relatively unchanged during 1988-2016. The latitudinal emissions shift is confirmed using the global distributions of the total column CH4 observations by satellite remote sensing. There is no evidence of emission enhancement due to climate warming, including the boreal regions, during our analysis period. These findings highlight key sectors for effective emission reduction strategies toward climate change mitigation.
著者
IWAKIRI Tomoki WATANABE Masahiro
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
pp.2020-064, (Released:2020-08-28)
被引用文献数
1

La Niña is the negative phase of the El Niño-Southern Oscillation (ENSO) cycle. It occurs in the equatorial Pacific, and events known as multiyear La Niña often persist for more than two years. During a conventional La Niña event, the seasonal cycle of surface temperature over Japan is known to be amplified (i.e. hotter summer and colder winter than normal years), but the influence of multiyear events on temperature over Japan has not yet been clarified. In this study, we evaluate the teleconnection associated with multiyear La Niña using composite analyses of observations, reanalysis data, and a large-ensemble of atmospheric general circulation model (AGCM) simulations for 1951-2010 driven by observed boundary conditions, and propose two distinct mechanisms involved in multiyear La Niña causing hot summers over Japan.  Composites of observational data show significant positive temperature anomalies over Japan in the boreal summer season preceding the two consecutive La Niña events reaching their mature phases. This robust summer signal can be reproduced by AGCM large ensemble simulations, which indicates that it is forced by multiyear La Niña. The time evolution of the anomalous summer temperature over Japan differs between the first and second years of multiyear La Niña. In the first summer, warm conditions are found in August–October in the southwestern part of Japan, due to anomalous southwesterly winds in the lower troposphere. This atmospheric circulation anomaly can be explained by a La Niña-induced decrease in precipitation over the equatorial western Pacific. In the second summer, warm anomalies are found in June–August over northeastern Japan, and these are accompanied by an anomalous barotropic high-pressure induced by negative precipitation anomalies over the equatorial Pacific. The seasonal march in atmospheric background states and the delayed effect of a preceding El Niño may explain the distinct teleconnection during multiyear La Niña.
著者
JUDT Falko KLOCKE Daniel RIOS-BERRIOS Rosimar VANNIERE Benoit ZIEMEN Florian AUGER Ludovic BIERCAMP Joachim BRETHERTON Christopher CHEN Xi DÜBEN Peter HOHENEGGER Cathy KHAIROUTDINOV Marat KODAMA Chihiro KORNBLUEH Luis LIN Shian-Jiann NAKANO Masuo NEUMANN Philipp PUTMAN William RÖBER Niklas ROBERTS Malcolm SATOH Masaki SHIBUYA Ryosuke STEVENS Bjorn VIDALE Pier Luigi WEDI Nils ZHOU Linjiong
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
pp.2021-029, (Released:2021-01-21)

Recent progress in computing and model development has initiated the era of global storm-resolving modeling and with it the potential to transform weather and climate prediction. Within the general theme of vetting this new class of models, the present study evaluates nine global-storm resolving models in their ability to simulate tropical cyclones (TCs). Results show that, broadly speaking, the models produce realistic TCs and remove longstanding issues known from global models such as the deficiency to accurately simulate TC intensity. However, TCs are strongly affected by model formulation, and all models suffer from unique biases regarding the number of TCs, intensity, size, and structure. Some models simulated TCs better than others, but no single model was superior in every way. The overall results indicate that global storm-resolving models are able to open a new chapter in TC prediction, but they need to be improved to unleash their full potential.
著者
Kentaro Araki Teruyuki Kato Yasutaka Hirockawa Wataru Mashiko
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.17, pp.8-15, 2021 (Released:2021-01-29)
参考文献数
48
被引用文献数
5

This study investigated characteristics of atmospheric environmental fields in the occurrence of quasi-stationary convective bands (QSCBs) in Kyushu, western Japan during the July 2020 heavy rainfall event. We performed case studies of extreme rainfall subevents in the Kumamoto and Kagoshima prefectures on 3-4 July (2020KK) and northern Kyushu on 6-7 July 2020 (2020NK), compared with two heavy rainfall events in northern Kyushu in 2017 and 2018.Nine QSCBs were objectively extracted during the July 2020 heavy rainfall event, causing hourly precipitation amounts exceeding 100 mm twenty times. In 2020KK, the environmental field with extremely large precipitable water due to low-level and middle-level humidity was affected by the upper-level cold airflow, which resulted in favorable condition for the deep convection development. Consequently, the lightning activity became high, and cloud tops were the highest in comparison to previous events. QSCBs in 2020KK and 2020NK were located along a low-level convergence line/zone associated with an inflow that had extremely large water vapor flux on the south side of the mesoscale Baiu frontal depressions. In most of the QSCB cases in 2020, mesoscale depressions were observed and enhanced horizontal winds, which led to extremely large low-level water vapor flux to produce short-term heavy rainfall.
著者
YAMADA Hiroyuki ITO Kosuke TSUBOKI Kazuhisa SHINODA Taro OHIGASHI Tadayasu YAMAGUCHI Munehiko NAKAZAWA Tetsuo NAGAHAMA Norio SHIMIZU Kensaku
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
pp.2021-063, (Released:2021-07-01)

Upper-tropospheric aircraft reconnaissance was carried out for Typhoon Lan (2017) using a civil jet with a newly developed dropsonde system. This was the first case of a Japanese research group observing the inner core of an intense typhoon using dropsondes. This paper describes the warm-core structure in the eye and the associated thermodynamic and kinematic features of the eyewall. During two days of reconnaissance, this typhoon preserved its peak intensity in an environment with a strengthening vertical shear. Dropsondes captured a double warm-core structure with a higher perturbation temperature in the middle and upper troposphere, which persisted between the two flight missions. The two warm cores show a difference in the equivalent potential temperature (θe) of more than 10 K, suggesting different air origins. Saturation point analysis suggest that air observed in the upper warm core was entrained from the eyewall. The eyewall updraft in the left-of-shear semicircle had a two-layer structure with a higher θe and lower absolute angular momentum on the inner side of the updraft core. Analyses of the saturation point and parcel method suggest that the warmer air with a θe exceeding 370 K on the inner side of the updrafts originated from the eye boundary layer and was eventually transported into the upper warm core. These results led us to hypothesize that the vertical transport of high-θe air from the eye boundary layer contributed to the continuous eye warming in the upper troposphere against the negative effect of a strengthening environmental wind shear on the storm intensity. This study demonstrates the significance of eyewall-penetrating upper-tropospheric reconnaissance for monitoring the warm-core structure in the present situation where accurate measurements of both humidity and temperature for calculating θe can only be made with dropsonde-type expendables.
著者
STEVENS Bjorn ACQUISTAPACE Claudia HANSEN Akio HEINZE Rieke KLINGER Carolin KLOCKE Daniel RYBKA Harald SCHUBOTZ Wiebke WINDMILLER Julia ADAMIDIS Panagiotis ARKA Ioanna BARLAKAS Vasileios BIERCAMP Joachim BRUECK Matthias BRUNE Sebastian BUEHLER Stefan A. BURKHARDT Ulrike CIONI Guido COSTA-SURÓS Montserrat CREWELL Susanne CRÜGER Traute DENEKE Hartwig FRIEDERICHS Petra HENKEN Cintia Carbajal HOHENEGGER Cathy JACOB Marek JAKUB Fabian KALTHOFF Norbert KÖHLER Martin LAAR Thirza W. van LI Puxi LÖHNERT Ulrich MACKE Andreas MADENACH Nils MAYER Bernhard NAM Christine NAUMANN Ann Kristin PETERS Karsten POLL Stefan QUAAS Johannes RÖBER Niklas ROCHETIN Nicolas SCHECK Leonhard SCHEMANN Vera SCHNITT Sabrina SEIFERT Axel SENF Fabian SHAPKALIJEVSKI Metodija SIMMER Clemens SINGH Shweta SOURDEVAL Odran SPICKERMANN Dela STRANDGREN Johan TESSIOT Octave VERCAUTEREN Nikki VIAL Jessica VOIGT Aiko ZÄNGL Günter
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
pp.2020-021, (Released:2020-01-28)
被引用文献数
25

More than one hundred days were simulated over very large domains with fine (0.156 km to 2.5 km) grid spacing for realistic conditions to test the hypothesis that storm (kilometer) and large-eddy (hectometer) resolving simulations would provide an improved representation of clouds and precipitation in atmospheric simulations. At scales that resolve convective storms (storm-resolving for short) scales, the vertical velocity variance becomes resolved and a better physical basis is achieved for representing clouds and precipitation. Similar to past studies we find an improved representation of precipitation at kilometer scales, as compared to models with parameterised convection. The main precipitation features (location, diurnal cycle and spatial propagation) are well captured already at kilometer scales, and refining resolution to hectometer scales does not substantially change the simulations in these respects. It does, however, lead to a reduction in the precipitation on the time-scales considered – most notably over the Tropical ocean. Changes in the distribution of precipitation, with less frequent extremes are also found in simulations incorporating hecto-meter scales. Hectometer scales appear more important for the representation of clouds, and make it possible to capture many important aspects of the cloud field, from the vertical distribution of cloud cover, to the distribution of cloud sizes, to the diel (daily) cycle. Qualitative improvements, particularly in the ability to differentiate cumulus from stratiform clouds, are seen when reducing the grid spacing from kilometer to hectometer scales. At the hectometer scale new challenges arise, but the similarity of observed and simulated scales, and the more direct connection between the circulation and the unconstrained degrees of freedom make these challenges less daunting. This quality, combined with an already improved simulation as compared to more parameterised models, underpins our conviction that the use and further development of storm-resolving models offers exciting opportunities for advancing understanding of climate and climate change.
著者
Tetsuya Takemi Takashi Unuma
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.15A, pp.60-65, 2019 (Released:2019-09-19)
参考文献数
32
被引用文献数
13

This study documented the environmental properties of precipitation systems that produced the July 2018 Heavy Rainfall event in Japan. The gridded analysis data were used to diagnose the potential for the development of convective systems in terms of thermodynamic environmental indices. Precipitable water vapor was extremely larger than that seen in the climatology of warm-season quasi-stationary convective clusters (QSCCs). Such an extreme moisture content was realized by very humid conditions at the middle-levels. In contrast, temperature lapse rate in a convectively unstable layer was not so significant in comparison to the QSCC climatology. Among the environmental indices, K Index was shown to describe the potential for the rainfall development. Based on the analysis, the roles of moisture content and profile on the convection development were discussed. It was suggested that the middle-level high humidity contributes to the occurrence of the present heavy rainfall by minimizing negative effects of environmental mixing and by decreasing vertical displacements to reach levels of free convection. In regions where heavy rainfall occurred, an automated algorithm detected the development of QSCCs, which were mostly categorized as a linear type.
著者
Tetsuya Takemi Toshiya Yoshida Shota Yamasaki Kentaro Hase
出版者
Meteorological Society of Japan
雑誌
SOLA (ISSN:13496476)
巻号頁・発行日
vol.15, pp.22-27, 2019 (Released:2019-02-06)
参考文献数
27
被引用文献数
13

An intense tropical cyclone, Typhoon Jebi (2018), landed the central part of Japan and caused severe damages. Quantitative assessment of strong winds in urban districts under typhoon conditions is important to understand the underlying risks. As a preliminary study, we investigate the influences of densely built urban environments on the occurrence of wind gusts in an urban district of Osaka City during Typhoon Jebi by merging mesoscale meteorological and building-resolving large-eddy simulations (LES). With the successful reproduction of the track and intensity of the typhoon in meteorological simulations, the simulated winds at the boundary-layer top of the LES model are used to quantitatively estimate the wind gusts in the urban district. The maximum wind gust in the analysis area of Osaka was estimated as 60-70 m s−1, which is comparable to the wind speed at the height of about 300 m.
著者
KATO Teruyuki
出版者
Meteorological Society of Japan
雑誌
気象集誌. 第2輯 (ISSN:00261165)
巻号頁・発行日
pp.2020-029, (Released:2020-03-24)
被引用文献数
7

In Japan, localized heavy rainfall events producing accumulated three-hour precipitation amounts larger than 200 mm are often observed to cause severe landslides and floods. Such events are mainly brought by quasi-stationary band-shaped precipitation systems, named “senjo-kousuitai” in Japanese. Senjo-kousuitai is defined as a band-shaped heavy rainfall area with a length of 50-300 km and a width of 20-50 km, produced by successively formed and developed convective cells, lining up to organize multi-cell clusters, and passing or stagnating at almost the same place for a few hours. The formation processes of senjo-kousuitai are categorized mainly into two types; the broken line type in which convective cells simultaneously form on a quasi-stationary local front by the inflow of warm and humid air, and the back building type in which new convective cells successively forming on the upstream side of low-level winds linearly organize with pre-existing cells. In this study, previous studies of band-shaped precipitation systems are reviewed, and the numerical reproducibility of senjo-kousuitai events and the favorable conditions for their occurrence are examined. In a case of Hiroshima heavy rainfall observed in western Japan on 20 August 2014, the reproduction of the senjo-kousuitai requires a horizontal resolution of at least 2 km, which is sufficient to roughly resolve the formation and development processes of convective cells, while a resolution of 250-500 m is necessary to accurately reproduce their inner core structures. The 2-km model quantitatively reproduced the Hiroshima case when initial conditions 10 hours before the event were used, but the predicted amounts of maximum accumulated precipitation were considerably reduced as the initial time became closer to the occurrence time of the senjo-kousuitai. This reduction was brought from the excessive inflow of low-level dry air that shifted occurrence areas of new multi-cell clusters.  Six favorable occurrence conditions of senjo-kousuitai events for their diagnostic forecasts were statistically constructed from environmental atmospheric fields in previous localized heavy rainfall events. Two conditions of (1) large water vapor flux amounts (> 150 g m−2 s−1) and (2) short distances to the level of free convection (< 1000 m) were chosen representatively for the low-level water vapor field that is judged based on 500-m height data. Four other favorable conditions are selected; (3) high relative humidity at midlevels (> 60 % at 500 hPa and 700 hPa), (4) large vertical shear estimated from the storm relative environmental helicity (> 100 m2 s−2), (5) synoptic-scale ascending areas (400 km mean field at 700 hPa), and (6) the exclusion of warm air advection frequently appearing at 700-850 hPa and inhibiting the development of convection (i.e., an equilibrium level > 3000 m).