Hai Wen Duidong Yaxia Monsoon Interdecadal And Interannual Variability Of The Winter Wind's Impact

East Asia experienced a significant interdecadal climate shift around the late 1970s, with more floods in the valley of the Yangtze River of central-eastern China and more severe drought in North China since then. Furthermore, snow and freezing-rain in January 2008 affected the Southern China and caused very serious damage. Whether global sea surface temperature (SST) has played a role in climate shift is unclear. In the present study, statistical analysis and numerical model are employed to investigate the impact of SST variations on the East Asian Monsoon, the main results are as follows:(1) The GFDL AM2 model simulates both the observed East Asian Summer Monsoon (EASM) and East Asian Winter Monsoon (EAWM) well.(2) The model results suggest that decadal global SST variations may have played a substantial role in this climate shift. Further examination of the associated atmospheric circulation shows that these results are physically reasonable. The interdecadal variation of tropical SST has more important effects on the climate shift of South Asia High(SAH), West Pacific Subtropical High(WPSH) and cross-equator air stream than extratropical SST.(3) By analyzing the observational data and conducting experiments in an AGCM GFDL AM2, we investigated the influence of the La Nina event. The results suggest that the strong La Ni(?)a can explain the colder climate and more precipitation than usual in South China, as well as the associated circulation anomalies like Mongolia Cold High. But, it can't explain the enhancements of the west Pacific subtropical high and the blocking high over the Ural Mountains. Subsequently, we discussed the influence of the North Atlantic warmth using the results from a previous modeling study, and speculated that the warmth has played an important role for the maintenance of the persistent blocking over the Urals. Thus, it is concluded that the disastrous climate event happened in January 2008 may be resulted from the coordinate interaction of several factors including strong La Nina and North Atlantic warmth. (4) The response of EAWM to ENSO events are analyzed by using the composite method based on the Nino 3.4 Index and NCEP/NACR reanalysis data with four categories of strong El Ni(?)o (La Ni(?)a) and moderate El Nino (La Ni(?)a) events. The results suggest that when the El Ni(?)o (La Ni(?)a) events are not strong, other factors may partly have influence the response of atmosphere on ENSO events.