Analysis on Precipitation Variation and Agricultural Drought and Flood Degree during the Crop Growing Season in Nanjing City from 1982 to 2011

The monthly precipitation and average temperature data from April to October during 1982-2011 in Nanjing City were selected,the precipitation variation and the agricultural drought and flood degree during the crop growing season in Nanjing City from 1982 to 2011 were analyzed from the aspects of natural precipitation tendency changes and agricultural water satisfaction degree of crops in growth period using the methods of linear regression,climate tendency rate and humidity index.The results showed that the average precipitation during the crop growing season in Nanjing City from 1982 to 2011 was increased by 30.2 mm every 10 years,the precipitation mainly concentrated in the June,July and August,and the precipitation of the three months accounted for 64.6% and the total precipitation during the crop growing season.The precipitation in Spring,Summer and Autumn respectively accounted for 20.0%,64.6% and 15.3% of the total precipitation during the crop growing season.The average K value during the crop growing season was 1.2,and was decresed by 0.01 every 10 years,it was the humid climate type.The drought occurrence frequency in Spring was 85% and mainly to light drought,the flood occurrence frequency in Summer was 36% and mainly to light flood,and there was no significant differences on the occurrence frequency of drought and flood in Autumn.