Analysis on cause of the flooding over the middle reaches of Yangtze Riverin 1998

With the data of geopotential height of 100 hPa and 500hPa, sea surface tem perature (SST), outgoing long-wave radiation (OLR) and rainfall and tempera ture data at Wuhan observatory, the causes of flooding over the middle reac hes of Yangtze River are analyzed. The results prove that the preceding int ensive signs benefiting to flooding appearance are the anomalous strong EL Nino and subtropical high in winter and spring, the abnormal vigorous cumul us convection in south to the ITCZ over Indian Ocean-West Pacific from spri ng to early summer and the abundant precipitation in winter.