Change features of precipitation events in Shandong Province from 1961 to 2010

Based on daily precipitation data of 121 weather stations in Shandong Province from 1961 to 2010, this paper analyzed the features of precipitation days and intensity including climate characteristics, trends, contribution rate, variation field, abrupt change and periodicity. The results indicated that with a significant drop of days, both annual precipitation days and intensity showed an obvious decadal oscillation. Annual precipitation days and intensity presented evident zonal distribution and gradually decreased from southeast to northwest. Precipitation intensity of heavy rainfall in various places were more uniform,meanwhile days and intensity of extreme rainfall were more and higher in mountain area of southern Shandong than in the northern part. There were 116 stations showing a decreasing trend of annual rainfall days and 80 stations presenting an increase of intensity. Furthermore,days of heavy rainfall decreased and intensity of extreme rainfall had become higher apparently. Heavy and extreme rainfall days on a small proportion, however contributed significantly to the annual precipitation. Since the 21st century, the days and precipitation percentage of heavy rainfall and extreme rainfall had an increasing trend. The average rainfall days and variation coefficient changed greatly in the mid-1960s, 1990s and early 21st century.Variation coefficient of different precipitation events showed similar decadal changes, while that of the same precipitation event in different decadal differentiated evidently. The average rainfall days and heavy rainfall intensity mutated in 1977 and 2005 respectively. Heavy rainfall and extreme rainfall days had variation major periods of 5 years and 11 years respectively, while precipitation intensity of different grades had periods of 13 years and 21years respectively.