Summer Precipitation Changes in Northeast Asia from the AOGCM Global Warming Experiments

In order to evaluate the model performance in simulating the Northeast Asian summer climate, and to investigate the effect of global warming on the summer climate over the Northeast Asian region, the multi-model ensemble of eight atmosphere-ocean coupled general circulation models in the historical (20C3M) and the scenarios (A2, A1B, B1) runs are analyzed, which is participating to the Intergovernmental Panel on Climate Change fourth Assessment Report (IPCC AR4). From comparison of the observation and the 20C3M experiment, it is found that the multi-model ensemble quite well simulates the Northeast Asian summer precipitation and circulation, especially in the first two empirical orthogonal function (EOF) modes and the associated regressed field. The first EOF mode represents the decaying phase of El Nino and Southern Oscillation (ENSO), which contributes to the development of the Philippines Sea anticyclone. The second one is associated with the fast transition of ENSO. In future climate, the increase of the precipitation to 2099 at A2, and A1B simulation reaches 10% compared with the mean precipitation for 1961-1990 over the Northeast Asian region. After the stabilization of the greenhouse gas concentration in 2100, the precipitation is enhanced during 30 or 50 years more due to the inertia inherent in the climate system. From EOF analysis, it seems that the increased Northeast Asian summer precipitation due to global warming is contributed by the effect of the enhanced monsoon circulation in the decaying phase of El Nino rather than the mean linear increase of global climate or the circulation in the fast transitional period of ENSO.