摘要
By using Season-reliant Empirical Orthogonal Function (S-EOF) analysis, three dominant modes of the spatial-temporal evolution of the drought/flood patterns in the rainy season over the east of China are revealed for the period of 1960-2004. The first two leading modes occur during the turnabout phase of El Nino-Southern Oscillation (ENSO) decaying year, but the drought/flood patterns in the rainy season over the east of China are different due to the role of the Indian Ocean (IO). The first leading mode appears closely correlated with the ENSO events. In the decaying year of El Nino, the associated western North Pacific (WNP) anticyclone located over the Philippine Sea persists from the previous winter to the next early summer, transports warm and moist air toward the southern Yangtze River in China, and leads to wet conditions over this entire region. Therefore, the precipitation anomaly in summer exhibits a 'Southern Flood and Northern Drought' pattern over East China. On the other hand, the basin-wide Indian Ocean sea surface temperature anomaly (SSTA) plays a crucial role in prolonging the impact of ENSO on the second mode during the ENSO decaying summer. The Indian Ocean basin mode (IOBM) warming persists through summer and unleashes its influence, which forces a Matsuno-Gill pattern in the upper troposphere. Over the subtropical western North Pacific, an anomalous anticyclone forms in the lower troposphere. The southerlies on the northwest flank of this anticyclone increase the moisture transport onto central China, leading to abundant rainfall over the middle and lower reaches of the Yangtze River and Huaihe River valleys. The anomalous anticyclone causes dry conditions over South China and the South China Sea (SCS). The precipitation anomaly in summer exhibits a 'Northern Flood and Southern Drought' pattern over East China. Therefore, besides the ENSO event the IOBM is an important factor to influence the drought/flood patterns in the rainy season over the east of China. The third mode is positively corr
By using Season-reliant Empirical Orthogonal Function （S-EOF） analysis, three dominant modes of the spatial-temporal evolution of the drought/flood patterns in the rainy season over the east of China are revealed for the period of 1960-2004. The first two leading modes occur during the turnabout phase of El Nino-Southern Oscillation （ENSO） decaying year, but the drought/flood patterns in the rainy season over the east of China are different due to the role of the Indian Ocean （IO）. The first leading mode appears closely correlated with the ENSO events. In the decaying year of El Nino, the associated western North Pacific （WNP） anticyclone located over the Philippine Sea persists from the previous winter to the next early summer, transports warm and moist air toward the southern Yangtze River in China, and leads to wet conditions over this entire region. Therefore, the precipitation anomaly in summer exhibits a ＇Southern Flood and Northern Drought＇ pattern over East China. On the other hand, the basin-wide Indian Ocean sea surface temperature anomaly （SSTA） plays a crucial role in prolonging the impact of ENSO on the second mode during the ENSO decaying summer. The Indian Ocean basin mode （IOBM） warming persists through summer and unleashes its influence, which forces a Matsuno-Gill pattern in the upper troposphere. Over the subtropical western North Pacific, an anomalous anticyclone forms in the lower troposphere. The southerlies on the northwest flank of this anticyclone increase the moisture transport onto central China, leading to abundant rainfall over the middle and lower reaches of the Yangtze River and Huaihe River valleys. The anomalous anticyclone causes dry conditions over South China and the South China Sea （SCS）. The precipitation anomaly in summer exhibits a ＇Northern Flood and Southern Drought＇ pattern over East China. Therefore, besides the ENSO event the IOBM is an important factor to influence the drought/flood patterns in the rainy season over the east of Chin
基金
supported by the National Basic Research Program of China (973 Program) (No. 2012CB955604)
the National Natural Science Foundation of China (Nos. 40975038, 40830106)
the CMA Program (GYHY200906008)
the 111 Project (B07036)
