著者

UNUMA Takashi TAKEMI Tetsuya

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.2021-009, (Released:2020-11-30)

被引用文献数

8

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In July of 2017 and 2018, heavy rainfall events occurred, leading to significant damage in Japan. This study investigated the rainfall characteristics and environmental conditions for these heavy rainfall events using rain intensity data from operational weather radars and mesoscale analysis data. An automatic algorithm was developed to categorize precipitating cloud systems into five types, one with weaker rainfall (less than 10 mm h−1) and four with stronger rainfall (greater than or equal to 10 mm h−1), i.e., quasi-stationary convective clusters (QSCCs), propagating convective clusters (PCCs), short-lived convective clusters (SLCC), and other convective but unorganized rainfall. The rainfall amount due to the weaker rainfall was found to dominate the total rainfall in most of the analysis region; however, the contribution from the stronger rainfall types became larger than that from the weaker rainfall type in regions that experienced heavy rainfall. Among the stronger rain types, SLCCs dominate over the rainfall contributions from QSCCs or PCCs, whereas rainfalls from convective but unorganized systems are very minor. It was emphasized that the contribution from stronger rains due to organized systems with areas of 200 km2 plays a major role in regions with significant amounts of rainfall during the heavy rainfall events examined here. The examination of the environmental conditions for the development of each system demonstrated that, from the viewpoint of moisture content, the stability conditions were more unstable in 2018 than in 2017. There is also a clear linkage in the time series between rainfall types and the environmental properties of precipitable water and vertical shear. It was found that both the column moisture content and the middle-to-upper-level relative humidity characterize the environmental conditions for the occurrence of the present heavy rainfall events. Features of the rainfall types and their environmental conditions were compared with the QSCC climatology.

著者

NAYAK Sridhara TAKEMI Tetsuya

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.2019-003, (Released:2018-10-29)

被引用文献数

13 27

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Typhoons are considered as one of the most powerful disaster-spawning weather phenomena. Recent studies have revealed that typhoons will be stronger and more powerful in a future warmer climate and be a threat to lives and properties. In this study, we conduct downscaling experiments of an extreme rain-producing typhoon, Typhoon Lionrock (2016) in order to assess the impacts of climate change on resulting hazards by assuming pseudo global warming (PGW) conditions. The downscaled precipitations over the landfall region in the present climate condition agree well with the Radar- Automated Meteorological Data Acquisition System (Radar-AMeDAS) observations. A typhoon track in the future climate similar to that in the present climate is successfully reproduced, with a stronger wind speed (by ~20 knots) and lower central pressure (by ~20 hPa) under the PGW condition. The changes in precipitation amounts associated with the typhoon under PGW condition are analyzed over 7 individual prefectures in the northern part of Japan. The typhoon in the warming climate produces more precipitation over all prefectures. Iwate, Aomori, Akita, Miyagi and Hokkaido are projected to have relatively more precipitation associated with the typhoon in the warming climate. The overall analysis suggests that Typhoon Lionrock under PGW may increase the risk of flooding, damages to infrastructures, and lives staying along the typhoon track.

著者

ITO Rui SATOMURA Takehiko TAKEMI Tetsuya

出版者

The Association of Japanese Geographers

雑誌

Geographical review of Japan series B (ISSN:18834396)

巻号頁・発行日

vol.87, no.1, pp.65-73, 2014-08-29 (Released:2014-10-03)

参考文献数

24

被引用文献数

2

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In order to reveal the relationships between physical-geographical conditions and temperature rises in cities, the dependence of the rate of surface air temperature rise on urban surface cover was compared for different physical-geographical conditions for cities in Japan. The monthly mean temperatures observed in 74 sites selected to fulfill specific criteria from 1964 to 2011 and land use data categorized into 11 types, at 100 m spatial resolution, including buildings and roads, were used. The rate of the monthly mean of the daily mean temperature rise for the coastal sites has a positive correlation with the distance from the coastline. The rate of temperature rise was found to be positively correlated with an urban cover index for the coastal observation sites within 7 km from the coastline, and for the sites including the coastal sites more than 7 km away from the coastline and the inland sites. The change in the rate of temperature rise with respect to the urban cover index is higher for the inland sites than for the coastal sites within 7 km of the coast. The largest difference in the rates is shown in winter. The rate of temperature rise at sites more than 7 km away from the coast is similar to those at inland sites. The study has implications for predicting future changes in cities and the greater vulnerability of inland cities to enhanced warming.