Characteristics And Mechanism Of Extreme Precipitation Changes In Eastern China Since The Mid-Holocene

Extreme precipitation is particularly harmful,especially in heavily populated monsoon areas.At present,the research on extreme precipitation mainly focuses on the evolution of extreme precipitation under the background of human-induced warming,and there are few studies on the natural variability and mechanism of extreme precipitation in the past geological period.Existing studies have not linked model simulations to paleoclimate reconstruction data.In addition,the relationship between extreme precipitation and precipitation at the suborbital scale is still unclear.Understanding the past is the key to predicting the future,and the mid-Holocene,as the warmest period in orbital timescales closest to the present,provides valuable reference for predicting climate change under warming.Based on the EC-Earth3 climate model with high spatial and temporal resolution,combined with existing paleoclimate reconstruction data,this paper studies the variation characteristics and mechanism of extreme precipitation in eastern China since the mid-Holocene,and further explores the relationship between extreme precipitation and precipitation at suborbital scales.We used paleoclimate reconstruction data to evaluate the reliability of model simulations,and used model simulations to delve into the mechanisms of extreme precipitation changes.Finally,based on the reliability of model simulations of extreme precipitation,we made further predictions of the future evolution of extreme precipitation in eastern China.The main findings are as follows:1.Model simulations and paleoclimate reconstruction data both indicate that extreme precipitation in eastern China has shown a north-south reversing trend since the mid-Holocene.In the north,extreme precipitation was stronger in the mid-Holocene and weaker in the late Holocene,while in the south,extreme precipitation was weaker in the mid-Holocene and stronger in the late Holocene,showing a dipole mode of reversing changes.2.Compared with the intensity of the monsoon,the duration of the rain period is the direct cause of the north-south reverse evolution of extreme precipitation.Cluster analysis shows that the East Asian summer monsoon dominates the extreme precipitation in North China.Compared with the pre-industrial revolution(Late Holocene),the allocation of orbital parameters in the midHolocene led to the warming of the middle and high latitudes in the northern Hemisphere,which increased the land-sea thermal difference and enhanced the East Asian summer monsoon.At the same time,the warming in the middle and high latitudes also weakened the north-south temperature gradient,making the westerlies move northward.The northward shift of the westerlies causes the monsoon to prevail earlier in North China,prolonging the rain period.The combination of the enhanced East Asian summer monsoon and the prolonged rain period led to the intensification of extreme precipitation in North China during the mid-Holocene.3.Cluster analysis showed that the extreme precipitation in the Yangtze River Basin is dominated by Meiyu rainfall.Compared with the mid-Holocene,the convection in the low latitudes during the pre-industrial revolution(Late Holocene)was weakened,the corresponding cloud cover was weakened,and the solar radiation reaching the surface was enhanced,which led to the warming in the low latitudes,thus strengthening the North-South temperature gradient and causing the westerlies to move southward.The southward shift of the westerlies causes the East Asian summer monsoon to stay longer in the Yangtze River Basin,prolonging the Meiyu period.The extension of the Meiyu period reversed the weakening of the East Asian summer monsoon and increased the extreme precipitation in the Yangtze River Basin during the preindustrial revolution(Late Holocene).4.Model simulations and paleoclimate reconstruction data both indicate that the changes in precipitation in eastern China since the mid-Holocene are similar to those of extreme precipitation,both showing a north-south reversing trend.Further analysis shows that although the changes in the two are similar,the changes in extreme precipitation did not cause changes in precipitation.5.Extreme precipitation will exacerbate with increased warming(SSP5-85 >SSP3-70 > SSP2-45 > SSP1-26).Extreme precipitation in the Yangtze River Basin,Yellow River Basin and central Northeast China will be more intense than in other parts of eastern China,indicating that these regions will suffer more severe extreme precipitation disasters in the future.Therefore,these regions should pay more attention to the prevention and management of extreme precipitation disasters in the future.