Change Of Precipitation Intensity And Its Influencing Facter In South China Under Global Warming

Impacted by human activities,global climate continues to get warmer,leading to significant changes in regional precipitation which is essential to agriculture,water resource and many other aspects.In this study,with the analysis of precipitation data from Dataset of Daily Climate Data from Chinese Surface Stations(V3.0),historical tracks of tropical cyclones(TCs)in IBTrACS(International Best Track Archive for Climate Stewardship)and CMIP5 AMIP simulations,the annual and seasonal change of precipitation intensity in South China(Guangdong,Guangxi,Hainan and Fujian Province)during 1967-2016 and its relationship with global temperature are discussed utilizing the Interannual Difference Method,and based on the Objective Synoptic Analysis Technique,the impacts of tropical cyclones to total precipitation are estimated quantitatively.Besides,the consecutive non-precipitation events and Standard Precipitation Evapotranspiration Index(SPEI)are also used to estimate the floods and droughts in South China.The major conclusions are shown as following:(1)In both annual and seasonal bases,a significant shift of precipitation intensity spectrum from light to heavy precipitation has been observed in station observations,and there are large uncertainties in CMIP5 AMIP simulations.Impacted by global warming,there is a significant enhancement of heavy precipitation and a reduction of light and moderate precipitation in both annual and seasonal bases,in other word,a significant shift of precipitation intensity spectrum from light to heavy precipitation.And driven by the great increase of heavy precipitation,the total precipitation amount also has an upward trend with respect to the increase of global temperature.With the comparsion of CMIP5 AMIP models with station observations,there is a significant underestimate in the precipitation and precipitation intensity,which suggest a low confidence in the model simulations.(2)The frequency of the tropical cyclones impacting South China descreases during 1967-2016,but the TC-related precipitation intensity increases significantly,which contributes a great part in the increase of the heavy precipitation.The main period in South China influenced by TCs occurs in June-Spetember,and the most active season is in July-September.With the increase of global temperature,the precipitation intensity of tropical cyclones has enhanced during 1967-2016 in all seasons,but a distinct seasonal discrepancy exits in the changes of TCs frequency: the TCs frequency reduces significantly in summer but changes slightly in autumn.In addition,the contribution of TC-related precipitation to total precipitation concentrates on the top 10% heavy precipitation,especially in autumn,when the averaged precipitation intensity of a single TC increased but no significant variation of TC frequency has been observed,leading to a larger enhancement of TC-related precipitation intensity than that in summer.Comparing the changes of total and TC-related precipitation,parts of the increase in top 10% precipitation is contributed by the TCs,especially in autumn with an astonishing contribution of 93.7%.(3)Under the context of global warming,the consecutive non-precipitaiton and heavy precipitation events increase significantly,and the risk and severity of flood and drought has also increased based on the analysis of Standarded Precipitation Evapotranspriation.The consecutive non-precipitation events(consecutive non-precpitaiton days ? 5,10,15,20 and 25 days)has increased with global temperature,especially in dry seasons,and an great anti-correlation(R=0.5-0.7)between consecutive non-precipitation events and days of bottom 10% precipitation has been observed.As a result,the reduction of bottom 10% precipitation may lead to an enhancement of consective non-precipitation events,which increase the risk of drought,especially in early spring which are detrimental to spring planting.In addition,the drought disasters increase significantly and an interdecadal variability has also observed,especially during 2007-2016.Although the simulations of surface temperature have high confidence level,there are large uncertainties in the simulation of precipitation and radiation in the 15 models of CMIP5 AMIP,leading to an insufficient simulation capacity of floods and drought in South China.