Climate Characteristics of Precipitation and Phenomenon of Drought-flood Abrupt Alternation during Main Flood Season in Huaihe River Basin

Huaihe River Basin locates in the north and south climate transition belt in China.The change rate of the inter-annual precipitation is obvious,and the flood-drought disaster occurs frequently in main flood season.Based on the precipitation data of 126 meteorological stations,the spatial-temporal distribution characteristics of the precipitation,the precipitation variations in typical dry-flood years and the phenomenon of drought-flood abrupt alternation during the main flood season in Huaihe River Basin were analyzed,by using EOF,linear-trend estimate and Mann-Kendall catastrophe test.The results indicated that the spatial distribution of the precipitation showed that there were more precipitation in the South,mountain areas and inshore areas,compared to the North,plain and inland.The drought and flood mainly occurred in the South.The inter-annual variation of precipitation was also significant,especially in the lately decade.The concentrating heavy rain mainly occurred in the first ten days of July.The phenomenon of drought-flood abrupt alternation frequently occurred.Its frequency had obviously increased since 2000.