地球温暖化予測における梅雨期の降水および大気場の変化

Abstract

This study focuses on atmospheric circulation fields during the baiu in Japan with global warming under the RCP scenarios. We use projection experimental data conducted using a 20km-, 60km-mesh global atmospheric model (MRI-AGCM3.2). The baiu front indicated by the north-south gradient of moist static energy moves northward in present-day climate, whereas this northward shift in future climate simulations is very slow during May and June. In future late baiu season, the baiu front stays in the northern part of Japan even in August. As a result, the rich water vapor is transported around western Japan and the daily precipitation amount will increase in August. In the mid-troposphere, the horizontal warm advection roughly corresponds to upward vertical pressure velocity, and shows northward migration as seen in the lower troposphere. Especially, the RCP 8.5 scenario is delayed compared to the RCP 4.5 scenario. This tendency is evident in the north-south term of 500-hPa warm advection in particular. In conclusion, a late of the baiu rainfall band northward and an increase in precipitation during late of the baiu season are apparent from the point of view of atmospheric fields.