5:15 PM - 6:30 PM
[ACG29-P05] Impact of recent warming in East Asian marginal seas on the torrential rainfall event occurred in Kyushu Island, Japan in July 2017
Keywords:convective system, latent heat flux, WRF
Torrential rainfall events tend to occur more frequently in Japan as well as many parts of the world. Attributing the events to the global warming is, however, a complicated task. Although the majority of the moisture that causes the torrential rainfall comes from the tropics and amount of moisture supply from the ocean surface is not large compared to the horizontal moisture transport from the south, this study has highlighted the importance of atmospheric moistening in the lower troposphere due to recent warming in the mid-latitude oceans. The torrential rainfall event that occurred in Kyushu Island in July, 2017 was selected as a typical test case in the torrential rainfall events during the Baiu rainy season in Japan. Numerical simulations in this study shows that fractional change of the amount of the precipitation due to the oceanic and atmospheric warming since 1980s is 6.8%, corresponding to 10.6 % increase per 1 K of sea surface temperature (SST) rise. It is larger than expected from the Clausius–Clapeyron relationship (~6%/K) and consistent with the previous data analysis study. The SST rise in the east Arian marginal seas plays a fundamental role in intensifying the conditionally unstable conditions in the lower troposphere and in turn increase the amount of precipitation. On the other hand, changes in precipitable water plays a secondary role.