The variability of East Asian summer monsoon in IPCC SRES scenario simulations

Using the IPCC 4th assessment model output dataset and the results of the coupled climate mode ECHO-G under IPCC SRES greenhouse-gas scenarios (A2, B2, A1B, B1), the regional climate over the East-Asian region is investigated. The objective of this study is to evaluate model performance to simulate the East Asian summer monsoon and the impact of global warming on the East Asian summer climate. Therefore, through the analyses of empirical orthogonal function and the related regressed field, the simulated current and future circulations in summer over the East Asian region are compared. In order to asses the uncertainties of the models, the ratio of greenhouse-gas-induced variation to the total variation is calculated.

We analyze the change of the interannual and the interdecadal variations due to the increased concentration of greenhouse gas by Northeast Asian summer monsoon index (Lee et al., 2005), which is defined using empirical orthogonal function analysis of precipitation. The change of the relationships between the circulation over East Asia and both the tropical sea surface temperature and the western North Pacific anticyclone is also identified using the index.