Abstract:Based on 753 stations' daily rainfall data from China Meteorological Administration,NCEP/NCAR daily reanalysis data from 1978-2007 and monthly extended reconstructed sea surface temperature(ERSST) data supplied by NOAA,the regional Meiyu periods during 30 years(1978-2007) over the Yangtze-Huaihe river valley(YHRV) are defined from a regional integration viewpoint.The characteristic of spatial inhomogeneous distribution of Meiyu rainfall is discussed based on EOF(empirical orthogonal function)analysis.In particular,the relationship between spatial inhomogeneous distribution of Meiyu rainfall and previous SST(sea surface temperature) is studied.The results show that in-phase change across the whole YHRV region is closely linked to the previous winter SST anomaly near the Sea of Okhotsk in North Pacific.When the SST is higher(lower) than normal,the winter monsoon tends to be abnormally weak(strong) and the next Meiyu is flood(drought).In addition,when the SST from South China Sea(SCS) to east of Taiwan and Philippines is lower(higher) than normal in May,the following Meiyu rainfall is also to increase(decrease).The south-north out-of-phase rainfall pattern over the YHRV is intimately associated with the previous fall and winter SST in middle Indian Ocean.When the middle Indian Ocean SST is abnormally high from last October to January,the wind shear at 850 hPa between the Yangtze and the Huaihe River is apt to come into being,which is favorable for "south flood and north drought" pattern in the YHRV region,and vice versa.The east-west out-of-phase pattern is related to the SST in the eastern and central tropical Pacific in previous autumn and winter.ENSO events may exert an effect on the east-west location of western Pacific subtropical high,which leads to the general circulation anomaly and the east-west out-of-phase pattern of Meiyu further.When the eastern and central tropical Pacific SST is abnormally high(low),which corresponds to warm(cold) ENSO events,the location of western Pacific subtropical high is more westward(eastward) than normal,which leads to "east dry and west wet"("east wet and west dry") pattern over the YHRV.