Effects Of Climate Change And Human Economic Activities On Extreme Precipitation Events In Different Sub-regions Of China

Extreme precipitation event is one of the most widely affected and most harmful natural meteorological disasters in China and even the world.The existing research results showed that climate change will lead to more frequent,more intense and longer duration of extreme precipitation events in some regions.As one of the most significant countries affected by extreme precipitation events,the economic and property losses caused by extreme precipitation events account for about 3%-6%of GDP per year in China.Therefore,it was very important to grasp the change law and driving mechanism of extreme precipitation events.This paper analyzed the temporal and spatial evolution of extreme precipitation events in China by using the precipitation data and circulation indexes data over 1961-2020,and determined the key circulation indexes that affect the extreme precipitation events with the lag of 1-12 months in 7 sub-regions(northwest desert area,inner mongolia grassland area,Qinghai Tibet plateau area,northeast humid and semi humid temperate area,north China humid and semi humid temperate area,central and South China humid subtropical area and South China humid tropical area).In calibration periods(1961-2010),the key circulation indexes and 9extreme precipitation indices(continuous dry days(CDD),continuous wet days(CWD),heavy precipitation days(R10),extra heavy precipitation days(R20),maximum one day precipitation(Rx1day),maximum five consecutive days precipitation(Rx5day),the precipitation of very wet days(R99p),precipitation intensity(SDII)and the total precipitation of wet days(PRCPTOT))can be used to construct multiple linear regression models with the lag of 1-12 months in 7 sub-regions.Combined with the data of circulation indexes in December 2020,9 EPIs(CDD,CWD,R10,R20,Rx1day,Rx5day,R99p,SDII and PRCPTOT)could be predicted in 7 sub-regions from January to December 2021.Based on the data of population and GDP in 2018,525 sites were divided into 6 socioeconomic development levels(site-scales)in China,and the effects of population and GDP changes on extreme precipitation events in different site-scales were studied.In addition,the change of extreme precipitation events has been further explored from site scale I to VI.Finally,based on greenhouse gas emission concentrations and key circulation indexes,the contribution of human economic activities and climate change to extreme precipitation events at different socioeconomic development levels were analyzed.The main results are as follows:(1)The number and types of the key circulation factors affecting the extreme precipitation events vary according to the sub-regions and lag time.The significance t-test and Pearson correlation analysis of 9 EPIs and 57 circulation indexes with the lag of 1-12 months in 7 sub-regions,the key circulation indexes with a significant(P<0.05)and|r|?0.3 were obtained.The results showed that the plenty of precipitation in sub-region VI and VII,so the values of the 8 EPIs which represented the humid type were high and showed increasing trend.The precipitation was relatively low in sub-region I,so the CDD value were high,but which showed a decreasing trend.The Rx1day with the lag of 11 months corresponded to the most key circulation indexes(including 23)in sub-region VI,and the CWD with the lag of 1 month corresponded to the least key circulation indexes(including 2)in sub-region VI.In addition,under the lag of 12 month,the North Africa Subtropical High Area Index(NAHAI),Asia Polar Vortex Area Index(APVA),North America Polar Vortex Area Index(NAPVA),Pacific Polar Vortex Intensity Index(PPVI),North Atlantic European Polar Vortex Intensity Index(AEPVI)and North Atlantic European Circulation Pattern Type C Index(ACCP)all corresponded to 9EPIs in 7 sub-regions.(2)Based on key circulation index,the prediction of extreme precipitation events in 7regions from January to December 2021.The circulation indexes in December 2020 can be used to predict 9 EPIs from January to December 2021 in 7 sub-regions.The results showed that the observation and simulation results of the calibration and verification period showed a good simulation effect.According to the projection results of 9 EPIs in different sub-regions from January to December 2021,the extreme humid events caused by heavy precipitation still need to be prevented in the summer in sub-regions VI and VII,while the extreme drought events with less precipitation were also prevented in sub-region I.Compared with different threshold values(20%,40%,60%and 80%)of 9 EPIs in the past 60 years,the projection of CDD values from June to October in 2021 were higher than those of previous years,while those from January,February,March and December were lower than those of previous years..The 8 EPIs which representing the humid type showed opposite laws.(3)Effects of different social and economic development levels on extreme precipitation events.According to the population and GDP data in 2018,525 sites were divided into 6 site-scales.The results showed that the annual average population,GDP and its linear slopes increased from site-scales I to VI,while the sites included in higher site-scale had higher risk of extreme humid events,while those in lower site-scales had higher risk of extreme drought events.In addition,the correlation between 6 EPI_LS and Popu _LS(or GDP_LS)at different site-scales also verified the uncertainty of the effects of human economic activities brought by socioeconomic development on extreme precipitation events.In general,as the increase of site-scales,5 EPI_LS(except CWD_LS)showed an increasing trend,which means the sites which belonged to the higher socio-economic development level will suffer the higher risk of extreme precipitation events.(4)The contribution of climate change and human economic activities to extreme precipitation events.Based on analysis of variance,the contribution of greenhouse gas emission concentration(human economic activities)and key circulation index(climate change)to extreme precipitation events was quantified.The results showed that the 4 greenhouse gas emission concentrations increased with time at different socioeconomic development levels.The greenhouse gas emission concentrations in northwest and northeast China were low,while those in central China,south China and east China were relatively high.The sites with higher socioeconomic development levels(e.g.,site-scale VI),the contribution of climate change to the effects of extreme precipitation events were also higher.In addition,the contribution of human economic activities to 6 EPIs(CDD,CWD,SDII,R95P,RX1DAY and PRCPTOT)?50%at some sites which included in the southeast region.For most sites in China,the contribution of climate change to all 5 EPIs(except CWD)?50%.This also showed that extreme precipitation events in China were mainly affected by climate change.