Study on mechanism elucidation of snowfall phenomena in metropolitan areas in Japan through high-resolution ensemble simulations

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K14557
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 17020:Atmospheric and hydrospheric sciences-related
• Research Institution: Japan, Meteorological Research Institute
• Principal Investigator: Araki Kentaro 気象庁気象研究所, 台風・災害気象研究部, 主任研究官 (40636031)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 南岸低気圧 / 大雪 / 数値シミュレーション

Outline of Final Research Achievements

In this study, we hypothesized that "heavy snowfall in the metropolitan area caused by south-coast cyclone is significantly influenced by the amount of water vapor supplied from the southern sea and the cloud structure of the low-pressure systems." To test this hypothesis, we conducted ensemble simulation analyses. By analyzing the cases from February 14-15, 2014, and January 22, 2018, it was suggested in both instances that the cloud structure and precipitation mechanisms of the low-pressure systems, the amount of water vapor supplied, and the atmospheric lower-layer temperature field before snowfall are critical factors for heavy snowfall in the metropolitan area. The January 22, 2018 case suggested that differences in the movement speed due to variations in the synoptic-scale environmental field and the characteristics of the low-pressure systems resulted in different precipitation periods in the metropolitan area, leading to distinctions between heavy snowfall and heavy rainfall.

Free Research Field

気象学

Academic Significance and Societal Importance of the Research Achievements

冬季首都圏の南岸低気圧による大雪は現状でも正確な予測が難しく、高精度予測のために実態解明研究が急務であった。しかし、事例数が少なく、そもそも研究が進んでいなかった。本研究では、アンサンブルシミュレーションを用いることで事例数の問題を解消し、大雪のメカニズムや、大雪と大雨を分ける条件などについて総観・メソスケールの環境場と低気圧の特性、雲・降水の構造に注目して解析を行った。ここで得られた知見は、予報現場での診断的予測技術の向上に資するだけでなく、数値予報モデルによる再現性向上にも資するため、冬季首都圏の雪氷災害の防止という意味で意義のある研究課題となった。