Spatial And Temporal Variation Characteristics Of Precipitation Over China During 1960-2014 Under Global Warming

Precipitation is the most basic link in water cycle,source of surface runoff and groundwater.Unbalance spatial and temporal distribution of precipitation is the direct cause of floods and droughts.And energy conversion process is with rainfall.Endothermic process happens when raindrops condenses,while exothermic process happens when precipitation evaporates.Precipitation also is the key physical process to connect weather,climate and water cycle,and the ultimate source of clean water in ecosystem,to be one of the important meteorological elements related to the national economy and people's livelihood.In China,precipitation distributes unevenly with frequent floods and droughts.IPCC fifth assessment report pointed out that global temperature increased over the past century.Global warming has been estimated to increase the content of atmospheric water vapor,to accelerate the hydrological cycle,and to increase the extreme precipitation events.In the context of global warming,a good understanding of precipitation variations over China is beneficial to effective management and control of water resource.The area of study is mainland China,and we divided mainland China into four regions(northwestern of China,northern of China,Tibetan plateau and northern of China).The data employed in this study is observational data of meteorological stations obtained from the China Meteorological Administration.We divided the precipitation intensity into three groups(light,moderate,and heavy precipitation)according to the custom method and widely used China Meteorological Administration standards.In this study,spatial and temporal trends for different groups of precipitation from 1960-2014 over China were determined and compared finally to get the spatio-temporal characteristics.The goals of this work were to: 1)determine the primary cause for changes in light rain days;2)analyze the relationship between heavy or extreme precipitation and local temperature;3)compare the correlation between different groups of precipitation and mean annual precipitation;4)compare the contributing proportions of light,moderate,and heavy precipitation to the changes in annual precipitation;5)calculate the contributions of frequency and intensity to changes in precipitation amount;and 6)detect trends of precipitation amount and latitude.The main conclusions were as follows:(1)During 1960-2014,there were obvious regional differences in the spatial distributions and trends in the precipitation amount,frequency,and intensity of total,light,moderate,and heavy precipitation.Annual precipitation amount over China did not show significant trend,while frequency decreased and intensity strengthened significantly.Events of extreme precipitation displayed significant increase and opposite trends for the light rain.(2)The decrease in light rain frequency precipitation intensity was mainly the result of decrease of light rain amount in China,and dominated the change of total precipitation frequency.Lower-tropospheric warming and the water vapor content in warm season were responsible for light rain reduction.Increases in lower-tropospheric temperature reduced light rain days over the entire China,while variations in water vapor content dominated regional trend differences in light rain days,which resulted in the increase over western China while decrease over eastern China for light rain days.(3)Heavy(extreme)precipitation amount,frequency,and intensity in the southern China exhibited significant increasing trends,and local warming climate partly explained these trends.In addition,more effect of warming was along with higher threshold of heavy precipitation.And,these findings were only determined in southern China.(4)Over China and four regions,heavy precipitation contributed the most to increase in total precipitation amount,while light precipitation dominated the decreasing trend in total precipitation frequency.Furthermore,there were less amount and frequency of light and moderate precipitation,and more in heavy precipitation.As a result,proportion of light precipitation in total precipitation amount decreased,while heavy precipitation increased.(5)Both precipitation frequency and precipitation intensity have important effects on trends of precipitation amounts.And we found that variations in precipitation amount were mainly contributed by precipitation frequency for total,light,moderate,and heavy precipitation over China and four regions.(6)In northwestern of China,we found that annual precipitation amount,frequency,and intensity increased with altitude,and the same as proportion of heavy precipitation contributing to total precipitation amount changes.