Trends in Summer Precipitation and Causes of Decreasing Light Rain Precipitation in Northeast China

Based on the daily precipitation, relative humidity, and air temperature data during 1961−2017 from 96 stations in Northeast (NE) China, through trend analysis and the Mann-Kendall test method, the climate change characteristics of light rainfall, moderate rainfall, heavy rainfall, and torrential rainfall in summer and the causes of the decreasing trend of light rainfall frequency over NE China are analyzed. The main results are as follows: A significant positive correlation exists between the total precipitation over NE China and all types of precipitation frequency and contribution, and the total precipitation is mainly influenced by the frequency and contribution of heavy rain. The decrease in light rainfall and moderate rainfall is the main cause of the decrease in total precipitation in summer over NE China, and the torrential rainfall influenced by the increase in the torrential rainfall contribution shows a rising tendency. Furthermore, an interdecadal abrupt change in light rainfall and light rainfall contribution occurred around 1993, and the interdecadal abrupt change in light rainfall contribution has resulted in the interdecadal abrupt change in light rainfall. A certain decreasing trend of the total precipitation at 72 stations over NE China 85 stations showed a certain decreasing trend of the light rainfall, among which 25 stations show a significant decreasing trend; moreover, 70 stations show a certain decreasing trend of moderate rainfall, among which only nine stations show a significant decreasing trend; the number of stations that show an increasing trend of heavy rainfall is comparable to the number of those that show a decreasing trend, and the number of stations that show an increasing trend of the torrential rainfall is greater than the number of those that show a decreasing trend. Regarding cloud formation, the effects of the changes in water vapor, temperature, and aerosol concentration on the reduction in light rainfall in NE China are analyzed. The results show that the global temperatures rising and increased aerosol concentration are the main causes of the decreasing light rainfall in NE China.