Impact of the Changjiang River discharge on torrential rainfall events over Kyushu

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K13006
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Natural disaster / Disaster prevention science
• Research Institution: Kagoshima University
• Principal Investigator: Kako Shin'ichiro 鹿児島大学, 理工学域工学系, 助教 (60709624)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 長江希釈水 / 領域大気モデル / 海洋循環モデル / 水蒸気フラックス / 双子実験 / 感度実験

Outline of Final Research Achievements

This study investigated the effects of the Changjiang River discharge (CRD) into the East China Sea (ECS) with regard to sea surface temperature (SST) and related atmospheric changes (such as torrential rainfall events) using the ocean general circulation model (OGCM) and regional climate model. Twin experiments, using a regional climate model with and without CRD used for the lower boundary conditions, revealed that the decrease in the SST dependent on the CRD contributes to the substantially increased precipitation in extreme events such as the one observed in July 2009 over Kyushu. This is because the change in SST related to the CRD significantly affects the field change of the moisture flux convergence. These results suggest that CRD significantly influences both ocean and atmosphere circulation systems over the ECS.

Free Research Field

海洋物理

Academic Significance and Societal Importance of the Research Achievements

東シナ海への長江からの淡水流入をテーマにした既往研究は、ほとんどが塩分、海色・濁度、生態系への影響を議論しており、Kako et al. (2016)で示されたような長江希釈水に起因した水温分布の形成・変動過程が、その直上の大気に与える影響や、集中豪雨などの激甚災害に与えるインパクトへの言及は皆無であった。本研究は数値実験を通して、長江希釈水が夏季東シナ海陸棚域の海面水温を低下させ、その水温低下によって励起される東シナ海上の大気応答が、集中豪雨の発生・発達に対し、統計的な有意性が見出される程度に寄与することを初めて示した。これらの成果は、国内外の主要な学会で発表した。