Future Projection of Tropical Cyclone Precipitation over Japan with a High-Resolution Regional Climate Model

Abstract

 This study evaluates possible changes in tropical cyclone (TC) precipitation over Japan under a future warmer climate using an ensemble projection generated by a non-hydrostatic regional climate model with a resolution of 5 km (NHRCM05) under the RCP8.5 scenario. NHRCM05 reproduces TC precipitation and TC intensity more accurately than does a general circulation model with a resolution of 20 km. The number of TCs approaching Japan is projected to decrease under the future climate, while the TC precipitation rate increases. As these two effects cancel each other out, total TC precipitation, and the frequency of the moderate TC precipitation that is usual under the present climate, shows no significant change. On the other hand, the frequency of extreme TC precipitation increases significantly because the intensification of the TC precipitation rate outweighs the reduction in TC frequency. The increase in the TC precipitation rate is caused primarily by the increase in water vapor around the TCs, which in turn results from the increase in environmental water vapor. The intensification and structural changes to TCs also contribute to the enhanced TC precipitation.