[A-CG32] 中緯度大気海洋相互作用

[ACG32-05] Interannual fluctuations of summertime heavy rainfall potentials based on two thresholds in western Japan

*望月 崇¹ (1.九州大学大学院理学研究院)

キーワード：極端降水、大規模アンサンブルシミュレーション、インド洋海盆昇温、北西太平洋亜熱帯高気圧

Heavy rainfall has recently garnered considerable attention due to changing climatic conditions. The potential amount of heavy rainfall also provides us with useful information towards discussing disaster prevention, while the potential chance of heavy rainfall has usually used so far. By analyzing a set of large-ensemble simulations using a global atmospheric model, here we demonstrated that two different physical processes in global climate variability control the interannual fluctuations of 99- and 90-percentile values of summertime daily rainfall (i.e., potential amounts) on Kyushu Island in western Japan. The 90-percentile values are closely related to large-scale horizontal moisture transport anomalies due to changes in the subtropical high in the northwestern Pacific, usually accompanied by basin-scale warming in the Indian Ocean. In contrast, tropical cyclone activity played a major role in changing the 99-percentile value. The potentials of both tropical cyclone intensity and existence density fluctuate largely owing to the sea surface temperature over broader areas of the tropical Pacific. Consequently, the potential chance of heavy rainfall represents decadal modulation due to the combined effect of these two physical processes controlling the potential amounts.