Characteristics and Cause Analysis of Variations in Light Precipitation Events in the Central and Eastern Tibetan Plateau,China,During 1961–2019

The Tibetan Plateau(TP)is one of the most sensitive areas and is more susceptible to climate change than other regions in China.The TP also experiences extremely frequent light precipitation events compared to precipitation of other intensities.However,the definition,influencing factors,and characteristics of light precipitation in the TP have not been accurately explained.This study investigated the variation characteristics of light precipitation with intensities(Pre)of 0.1-10.0 mm/d based on climate data from 53 meteorological stations over the central and eastern TP from 1961 to 2019.For detailed analysis,light precipitation events were classified into five grades:G1[0.1-2.0 mm/d),G2[2.0-4.0 mm/d),G3[4.0-6.0 mm/d),G4[6.0-8.0 mm/d),and G5[8.0-10.0 mm/d).The results showed that both the amount of precipitation and number of precipitation days had increased significantly at rates of 4.0-6.0 mm/10 yr and 2.0-4.0 d/10 yr,respectively,and most precipitation events were of low intensity(0.1≤Pre<2.0 mm/d).Light precipitation events mainly occurred in the southeast of the study area,and it showed an increasing trend from the northwest to the southeast.Abrupt changes in light precipitation primarily occurred in the 1980 s.A comprehensive time series analysis using the Mann-Kendall test and Morlet wavelet was performed to characterize the abrupt changes and cycles of light precipitation.During the study period,the main periods of light precipitation corresponded to the 6 yr cycle,with obvious periodic oscillation characteristics,and this cycle coexisted with cycles of other scales.Significant correlations were observed between the amount of light precipitation and temperature over the study area.The findings will enhance our understanding of changes in light precipitation in the TP and provide Scientific basis for the definition of light precipitation in the future.