Abstract: Based on the precipitation data from June to August of Anhui province during 1961-2009,the spatial-temporal distribution and variation of precipitation were analyzed by using the Precipitation Concentration Degree(PCD) and Precipitation Concentration Period(PCP) in main flood season,and the PCD were compared between more precipitation year and less precipitation year.The results showed that the PCD and PCP could quantitatively represent the non-uniformity properties of the precipitation spatial-temporal distribution.The spatial distribution increasing trend of PCD and PCP were obvious from south to north over Anhui province during main flood season;the inter-annual and inter-decadal variations of PCD and PCP were obvious.EOF analysis showed that the ratio of the front three eigenvectors with total square error was 57%.The first eigenvector represented the conformity PCD variation over Anhui province,the second eigenvector represented the reverse PCD variation between the south and north,and the third eigenvector showed that the reverse PCD variation between south-north and the central region.The synthetic analysis showed that the PCD in more precipitation years was greater than that in less precipitation years,and the PCP was smaller than in the less precipitation years.The gravity of precipitation and its corresponding periods could be extracted by using the PCD and PCP method,which could provided the basis for the formation mechanism of extreme precipitation events.

Key words: Precipitation Concentration Degree(PCD), Precipitation Concentration Degree(PCD), Spatial-temporal distribution, Main flood season, Anhui province