Climatology and Interannual Variability of East Asian-Western Pacific Summer Monsoon Simulated by CMIP5 Models

Abstract:

The complex East Asian Summer Monsoon (EASM) system has provided a rigorous test bed for climate models. However, how to reliably reproduce the climatological rainfall and inter-annual variation of EASM remains to be a challenge for climate modeling community. In this seminar, the improvements of EASM simulation from CMIP3 to CMIP5 are assessed. The crucial dynamical processes that determine the model performance in reproducing the inter-annual variability of EASM are revealed. We show evidences that there is a skill dependence on Indian Ocean-western Pacific anticyclone tele-connection, viz. the tropical eastern Indian Ocean (IO) rainfall response to local warm SST anomalies in El Nino decaying year summer and the associated Kelvin wave response over the Indo-western Pacific region are important to maintain the Western Pacific anticyclone (WPAC). A successful reproduction of inter-annual EASM pattern depends highly on the IO-WPAC tele-connection. A further comparison of offline AGCM and fully coupled CGCM simulations of CMIP5 models indicate that the inter-annual EASM pattern is better simulated in CGCMs than that in AGCMs, thus the air-sea coupling process significantly improves the simulation. The underlying mechanisms are discussed.