Analyses of Extreme Precipitation Associated with the Kinugawa River Flood in September 2015 Using a Large Ensemble Downscaling Experiment

• FUJITA Mikiko

  Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan

• SATO Tomonori

  Faculty of Environmental Earth Science, Hokkaido University, Hokkaido, Japan

• YAMADA Tomohito J.

  Faculty of Engineering, Hokkaido University, Hokkaido, Japan

• KAWAZOE Sho

  Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan

• NAKANO Masuo

  Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan

• ITO Kosuke

  University of the Ryukyus, Okinawa, Japan

Abstract

 We investigated extremely heavy precipitation that occurred around the Kinugawa River, Japan, in September 2015, and the probability of extreme precipitation occurrence, using data from a large ensemble forecast of more than 1,000 members that were dynamically downscaled to 1.6 km horizontal grid spacing. The observed event was statistically rare among simulated cases and the 3-day accumulated precipitation around the target area was equivalent to the 95th percentile among all simulated ensemble members. Our results show that this extreme precipitation event occurred under specific conditions: two coexisting typhoons at close proximity that produced a high atmospheric instability, and water vapor transported from the Pacific Ocean. We also assessed the probability of extreme precipitation in mountainous areas other than the Kinugawa River case. Heavy precipitation also occurred southwest of the Kinugawa River region due to two typhoons, similar to the Kinugawa River case. The tracks of these typhoons shifted marginally; however, there was a difference in the water vapor supplied to the area, causing heavy precipitation. The large-ensemble downscaled data used in this study hence enabled us to evaluate the occurrence probability of a torrential rainfall event that was rarely observed, which may contribute to updating a disaster-mitigating plan for possible similar disasters in future.

Journal

• Journal of the Meteorological Society of Japan. Ser. II

  Journal of the Meteorological Society of Japan. Ser. II 97 (2), 387-401, 2019

  Meteorological Society of Japan

Keywords

• extreme precipitation
• ensemble forecast
• downscaling
• disaster prevention

Details

• CRID: 1390564238097876864
• NII Article ID: 130007623951
• DOI: 10.2151/jmsj.2019-022
• ISSN: 21869057
• ISSN: 00261165
• Web Site: https://www.jstage.jst.go.jp/article/jmsj/97/2/97_2019-022/_pdf
• Text Lang: en
• Data Source:
  • JaLC
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed