Future precipitation changes during summer in East Asia and model dependence in high-resolution MRI-AGCM experiments

Abstract

Global warming experiments using high-resolution climate models are important for studying the impact of global warming on human society from region to region. Three different cumulus schemes (YS: Yoshimura, KF: Kain-Fritsch and AS: Arakawa-Schubert) in the high-resolution Meteorological Research Institute AGCM have simulated slightly different future summer mean precipitation changes in East Asia, which are not negligible in the context of regional climate change. Specifically, 25-year mean June-July-August (JJA) average precipitation clearly decreases over eastern Japan, and tends to increase over northern Japan in YS. However, in KF and AS, decreases in precipitation are not significant over Japan, and an increase is clear from central China through southwestern Japan. Addtionally, the increase is extended over the Pacific side of Japan in KF.

The above dependence of future changes in precipitation in East Asia on the scheme used is interpreted by comparing future changes in water and heat balances in the atmosphere. Among possible global warming effects, scheme dependence is attributed to different changes in mean vertical velocity associated with southward shift of the westerly jet over the northern Pacific and weakened Asian monsoon circulations over Eurasia.