Characteristics And Causes Of The Persistent And Non-persistent Extreme Precipitation In Summer In China

To better understand the persistent structural changes of extreme precipitation in China and the causality for their changes and to provide scientific basis for climate change response and control of flood or other disasters,based on daily gauge precipitation data of 2480 stations from 1961 to 2016,the summer extreme heavy rainfall was determined based on 95% quantile threshold,the trend and characteristics of persistent and non-persistent extreme precipitation in China were analyzed by linear trend analysis,synthetic analysis,SVD method,water vapor transport decomposition and filtering method,the causes of extreme precipitation change were analyzed from the respective of atmospheric circulation and water vapor flux changes.The results indicate that:(1)extreme rainfall in most parts of China,especially in the Yangtze-Huaihe River Basin,and the contribution of extreme precipitation to total precipitation both showed increasing trends under the background of climate warming.Extreme rainfall tended to decrease only in North China and Southwest China,and the contribution of extreme precipitation to total precipitation was decreasing in the central part of Inner Mongolia and the Sichuan Basin.The distribution of extreme precipitation and total precipitation were similar and the distribution of change trends were also consistent.It indicated that the changes of total precipitation in China was dominated by extreme precipitation changes over the past 50 years.(2)The persistent and non-persistent extreme precipitation tended to increase in most parts of China but showed a decreasing trend in North and Southwest China.Extreme precipitation has become more non-persistent in North China and Southwest China in recent years but more persistent in the Jianghuai region and South China.Specifically,both persistent and non-persistent extreme precipitation showed decreasing trends in North and Southwest China,especially persistent extreme precipitation.Meanwhile,both types of extreme precipitation increased gradually in Jianghuai region and South China,especially persistent extreme precipitation.(3)From the perspective of large-scale circulation changes,it showed that the SAH strengthened eastwardly,while the strength of the three major blockings increased and the WPSH was strengthened after the 1990 s,which was favorable to the extreme precipitation in the Yangtze River basin and southern China.At the same time,the East Asian summer monsoon weakened and the water vapor transport conditions from the Bay of Bengal deteriorated,resulting in less extreme precipitation in North China and Southwest China.From the perspective of the combination of extreme precipitation and atmospheric circulation factors analyzed by Singular Value Decomposition method,the first mode showed that with more extreme precipitation in northeastern southern China,the intensified and westward extended WPSH was coincided with deepened IBT,enhanced Asian monsoon,and three increased blockings,while an inverse correlation showed up between the intensity of the above indices in North China.The second mode indicated that when more extreme precipitation occurred in North China and South China,the intensity of the WPSH north ridge and northern boundary were stronger,while the Southwest and Northeast China were negatively related to the intensity of the above indices.(4)Further the water vapor flux and its divergence over four regions(North China,Jianghuai region,South China and Southwest China)were decomposed and filtered.The results showed that the vapor flux divergence brought by large-scale stationary waves were enhanced over the Jianghuai region and South China,which was conducive to the extreme precipitation increase.Furthermore,the duration of convergence of water vapor flux determined the sustainability of extreme precipitation.The sudden change and the stable convergence of water vapor flux and showed an increasing trend,which caused the increasing of both sustainable and unsustainable in those regions.The weakening of the unsustainable(sustainable)convergence of water vapor flux caused the reduction of nonpersistent(persistent)extreme precipitation in North China and Southwest China.