The ENSO-Asian Monsoon Interaction In A Coupled Ocean-Atmosphere GCM

In this study, we evaluate the El Ni?o-Southern Oscillation (ENSO)-Asian monsoon interaction in a version of Hadley Center coupled ocean-atmosphere general circulation model (CGCM), known as HadCM3, based on a 1000-yr control integration under pre-industrial CO₂ concentration. The evaluation of this interaction is mainly focused on the two evolving anomalous anticyclones: one located over the western North Pacific (WNP) and the other over the south Indian Ocean (SIO). It is found that the HadCM3 can well simulate the main features of the seasonal evolution of both the anticyclones. The WNP anticyclone forms in the El Nino growing autumn, grows in the El Nino mature winter and the following spring, and decays in the subsequent summer, respectively. The SIO anticyclone evolves in the same manner in the El Nino growing summer, the subsequent autumn, and the following two seasons. Besides, this model also has a good simulation of the observed SST dipoles associated with the two anomalous anticyclones for their amplification. Associated with these anomalous anticyclones are the dipolar precipitation anomalies in the Indian Ocean prior to the El Ni?o mature and reduced precipitation in the tropical WNP after the El Ni?o mature. The simulated results by the model also indicate that strong ENSO-monsoon interaction is associated with the biennial tendency in the ENSO cycle and the Asian monsoon system. Strong El Ni?o events tend to be followed by a more rapid decaying phase and are much more likely to be turned to the La Nina events in the subsequent winter. Corresponding to strong El Ni?o events, the evolving SIO and WNP anticyclones exhibit a clearer biennial tendency.HadCM3's reasonably reproducing of the ENSO-Asian monsoon interaction provides one of the crucial bases to study the change of the ENSO- Asian monsoon interaction on the interdecadal timescale or in the global warming scenario.