Study On Variation Characteristics Of Extreme Climate Events And Drought-Humid In Xinjiang

Due to the impact of climate change,extreme weather events occur frequently in the world,significant changes had also taken place in the regional drought and humid conditions,which will cause a series of negative effects on economic and social development.Therefore,studying the temporal and spatial evolution,distribution characteristics,change mechanisms,and future change trends of extreme climate events and dry and wet variaitions played important role in reducing the impact of such abnormal climate events on the economy and society.Combined observed daily precipitation data from 61 meteorological stations and Climatic Research Unit(CRU)TS4.03 gridded data were selected to analysis the regional extreme climate and dry and wet variations.Six extreme precipitation indices and eight extreme temperature indices were selected to measure the extreme climate events,and the standardized precipitation evapotranspiration index(SPEI),which comprehensively considers precipitation and evapotranspiration,was utilized to quantitatively describe the change of dry and wet.First of all,the K-means clustering was used to divide Xinjiang into 4 sub-regions with distinct characteristics according to the interannual SPEI.The characteristics of extreme climates,drought and humid changes in Xinjiang from 1963 to 2018 were comprehensively analyzed.This manuscript revealed the influence of the North Atlantic Oscillation(NAO)on the extreme climate and drought and humid changes in the region.And CMIP6 model was used to predict the future evolution trend from 2025 to 2055,and the following conclusions are drawn:(1)On the whole,the four sub-regions of Xinjiang have shown trend of warming and humidification in the past 56 years,and extreme precipitation changed more frequently,while extreme temperature indices had longer variations periods.In terms of spatial distribution,most of the extreme temperature indicices of 61 meteorological stations showed significant trends,while the extreme precipitation indices rarely showed significant changes which were mostly located in the northern region.(2)The time points of drought to humid transition in different meteorological subregions were slightly different,but mainly concentrated in 1987,and the dry-wet transition in Xinjiang had longer period of variations,mainly concentrated in 8-16 years.The values of SPEI in Xinjiang were domainted by positive trends,only small areas showed significant increasing trends in spring.Xinjiang had experienced high frequency of droughts in the past 56 years and parts of Hotan in the south with low frequency of droughts.(3)NAO was the main cause of extreme precipitation in Xinjiang,but its impact on extreme temperature was not obvious which mainly concentrated on smaller time scales.NAO had greater impact on the drought-humid changes in Xinjiang in summer.After the 1980s,NAO played a role in promoting the regional drought and humid changes.(4)In the future scenario,our results indicated that Xinjiang will be humid in the future,and the distribution of precipitation will be more even,and extreme weather events will be reduced.In terms of drought and humid variations,the values of SPEI were lower than in the historical period,basically with mild and moderate humid events.In the future,the eastern part of Xinjiang will be the area with higher frequency of drought in spring and summer,while in autumn and winter,the northern regions.