Change Features of Different Types and Grades of Precipitation Event in Northeast China in Recent 50 Years

Using the daily precipitation data and daily temperature data at 90weather stations in Northeast China from 1961to 2010,the climate characteristics,trends and variation field characteristics of different grades in precipitation events have been studied.The results show that the trend of annual mean temperature increases in the past 50years,with higher increasing rate than other areas of China.An abrupt change temperature occurred in 1987,followed by a sharp increase in temperature.Annual precipitation and precipitation days decrease,with the decrease of annual precipitation days being more obvious,which is mostly due to the decline in light rainfall(days).Annual rainfall(days)shows the increasing trend,with annual snowfall(days)showing a decreasing trend.Annual precipitation decreases from southeast to northwest,and the annual number of precipitation days is larger in the east and north.The proportion of extreme heavy precipitation and different grade snowfall increase after temperature has abrupt change.The fluctuations of annual precipitation(days)also become larger after 1987,which may be the main reason of increase of extreme drought and flood events in Northeast China.The seasonal distribution of precipitation also shows significant changes.Rainfall(days)in summer and autumn are reducing,and rainfall(days)in spring and snowfall(days)in winter are increasing,which will be beneficial to maintain the soil moisture in winter and snow in spring.