Characteristics of precipitation division and controlling factors of summer precipitation in Liaoning province

Based on the monthly average precipitation data from 1961 to 2000 in Liaoning province,precipitation regions were divided into 4 regions.And inter-annual,inter-decadal,seasonal and cycle characteristics were analyzed in the different subareas.The results show that precipitation reduces obviously in the south and southeast of Liaoning province.Precipitation reduces obviously in the south and southeast of Liaoning province since 1990s,while precipitation increases in the middle of Liaoning province.Precipitation decreases in summer and winter in the southeastern region and in winter in the southern region,while precipitation increases in spring in the western region.The cycles in spring and winter are 2 a and 4 a,respectively.However,the cycles in both summer and autumn are 10 a.The controlling factors of summer precipitation are different in each subarea.East Asian trough deepens obviously in rainy year in the south of Liaoning province,while it deepens a little and leans to the east in rainy year in the southeast of Liaoning province.The relationship between summer precipitation and subtropical high pressure is significant.There is an obviously negative relationship between summer precipitation and sunspot in the south and southeast of Liaoning province,especially in August.The correlations in the south and middle of Liaoning province are significant,followed in the southeast and west of Liaoning province.