Changes in mean atmospheric structures around Japan during July due to global warming in regional climate experiments using a cloud-system resolving model

概要

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Regional climate experiments using a cloud-system resolving non-hydrostatic model with a horizontal resolution of 5 km are conducted in order to project changes in precipitation extremes in the vicinity of Japan during the warm season due to global warming. The results of a global 20-km model from May to October for 10-year periods in the present and future climates are adopted as the initial and boundary conditions. The simulated results project an increment in 90th-percentile values of daily precipitation on the Pacific side of the Japanese Islands during July in the future climate. Monthly mean fields during the month in the future climate show that abundant specific humidity of 20 g kg-1, 3 g kg-1 larger than that in the present climate, is supplied from the Pacific Ocean. In the future climate, mean equivalent potential temperature reaches 370 K near the sea surface south of western Japan, while a middle-level (around 5 km) drier region extends from the Asian Continent to the northwestern part of western Japan. As a result, convective instability is intensified in the vicinity of Japan and intense, deep convective systems form on the Pacific side of Japan.