Remort impacts of convection activity over the Tibetan Plateau on summer extreme weather condition in Japan

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K04095
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17030:Human geosciences-related
• Research Institution: Japan Agency for Marine-Earth Science and Technology
• Principal Investigator: Sugimoto Shiori 国立研究開発法人海洋研究開発機構, 地球環境部門(環境変動予測研究センター), 研究員 (90632076)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 夏季天候 / 東アジア / 領域大気モデル / チベット高原

Outline of Final Research Achievements

Numerical experiments with 20-km horizontal resolution (Ctl) were conducted over Asia from April to September for 25 years, and preciptiation bias in June was analyzed. Simulation accuarcy in precipitation was controled by a drier and colder bias associated with a weakning of the western North Pacific high and a higher bias of the geopotential height in the upper troposphere. A sensitivity experiment (Sen), which have an inner domain with 4-km horizontal resolution over the Tibetan Plateau in the Ctl, was also conducted focusing on the hot summer in 2010. In the Sen, the bias of geopotential height at 200 hPa was small relative to that in the Ctl because the stronger convection over the Tibetan Plateau excites a wave train. Furthermore, simulated geopotential height at 850 hPa in the Sen is also closer to the reanalysis over Japan. Due to higher pressure conditions in the upper and lower troposphere, a cold bias over Japan in the Ctl was ameliorated approximately 20－50% in the Sen.

Free Research Field

気候学

Academic Significance and Societal Importance of the Research Achievements

数値シミュレーションにて夏季降水の再現精度を向上させるためには、水蒸気輸送量を左右する太平洋高気圧の発達と中緯度上下層で連動する循環場を適切に再現する必要があることが分かった。また、猛暑形成に着目した場合、チベット高原の雲活動を起点とした中緯度循環場の遠隔作用が日本の気温再現に重要な役割を果たすことが示唆された。これらの学術的成果は、太平洋上だけでなくチベット高原上での対流活動を適切に再現することで、日本の夏季天候予測の再現性が向上する可能性を示す。また、一部の数値実験データを国際プロジェクトに提供し学術的に貢献した。