Spatio-temporal Change Of The Persistent Extreme Precipitation Over China And The Future Projections

Extreme precipitation has strong uncertainty of duration.The extreme precipitation event persisting for multi-days may cause great disaster.In fact,due to the uncertainty of the duration of extreme precipitation,the change of persistent extreme precipitation may be more complex than the change of extreme precipitation based on fixed time period recognized in the past,and the research on the persistent extreme precipitation events occurring in different time scales is more practical.In this study,China is divided into Mongolia-Xinjiang region,Qinghai-Tibet region and Eastern region.Based on the daily precipitation grid data set,monthly temperature grid data set,CMIP6 multi-mode ensemble data and atmospheric circulation index data from 1961 to 2018 in China,this study analyzes the spatio-tamporal changes and causes of the occurrence frequency of persistent extreme precipitation(PEPF),number of persist days(PEPD),total annual persistent extreme precipitation(PEPA),maximum annual persistent extreme precipitation(Rx Event),contribution rate of persistent extreme precipitation to total extreme precipitation,contribution rate of persistent extreme precipitation to total precipitation.The results show that:(1)In the past 60 years,the average frequency and duration of persistent extreme precipitation in Mongolia-Xinjiang region and Qinghai-Tibet region were higher,but the average annual total precipitation and annual maximum precipitation of persistent extreme precipitation in Eastern region were higher than the other regions.The frequency of persistent extreme precipitation in eastern China was lower than the other regions,but the intensity was higher,which made it more prone to serious floods.(2)From 1961 to 2018,significantly increasing trends were observed among the PEPF,PEPD,PEPA and Rx Event in China.On the regional scales,we found significantly increasing trends of the frequency and intensity of persistent extreme precipitation in the Mongolia-Xinjiang region and the Qinghai-Tibet region,while there was no significant change in the eastern region.In terms of spatial distribution,the trends of PEPF,PEPD,PEPA and Rx Event had similar spatial patterns.The fastest increasing rate of persistent extreme precipitation events were mainly at the junction of Mongolia-Xinjiang region and Qinghai-Tibet region.From 1961 to 2018,both extreme precipitation and total precipitation in China showed increasing trends.Under the background,the contribution rate of persistent extreme precipitation to total extreme precipitation had no obvious change trend,but the contribution rate of persistent extreme precipitation to total precipitation showed a significant increasing trend.The persistence and extremes of precipitation in China were increasing.(3)The results based on CMIP6 multi model set show that the distribution pattern of the multi-year mean value of each index of the persistent extreme precipitation in China in the future(2015-2099)is similar under the scenarios of SSP1-2.6,SSP2-4.5 and SSP5-8.5.The spatial distribution of the future mean values of PEPF and PED is similar.Under different scenarios,persistent extreme precipitation occurs more frequently and lasted longer in the southern part of Qinghai-Tibet region and the southern part of Mongolia-Xinjiang region.The spatial distribution of future mean values of PEPA and Rx Event are similar,which are increasing from west to east and from north to south in different scenarios.(4)The frequency and intensity of persistent extreme precipitation in China from2015 to 2099 show a significantly increasing trend,and the frequency and intensity of persistent extreme precipitation in Qinghai-Tibet region show the largest change trend in the future.At both regional and national scales,the trend of each persistent extreme precipitation index increased with the enhancement of radiation forcing scenario(SSP5-8.5 > SSP2-4.5 > SSP1-2.6).In the future,extreme precipitation and precipitation in China show a significantly increasing trend under different scenarios.Under this background,the contribution rate of persistent extreme precipitation to total extreme precipitation and total precipitation in China still show a significantly increasing trend under different scenarios.(5)There are significant correlations between the western Pacific subtropical high,the South China Sea subtropical high,the western Pacific warm pool,the Asian polar vortex,the northern hemisphere polar vortex and the persistent extreme precipitation events in China.On the regional scale,the western Pacific subtropical high has the greatest impact on Mongolia-Xinjiang region and Qinghai-Tibet region,while the eastern region is greatly affected by the western Pacific subtropical high and the western Pacific warm pool.Generally speaking,the western Pacific subtropical high has the greatest impact on China's persistent extreme precipitation events,the strengthening of the western Pacific subtropical high will lead to more persistent extreme precipitation in China.(6)The results show that the rate of change of persistent extreme precipitation with temperature in China is 14.18%/?,and the rate of change of PEPA with temperature in the Qinghai-Tibet region is the largest at the regional scale.Under SSP1-2.6,SSP2-4.5 and SSP5-8.5 scenarios,the change rates of PEPA with temperature in China are12.93%/?,13.10%/? and 13.55%/?.Although the change rates of China's PEPA with temperature under different scenarios are similar,the spatial distribution of PEPA is quite different.The results based on observation data and CMIP6 multi-mode ensemble data show that the response of persistent extreme precipitation to temperature change is stronger than that of extreme precipitation.