Assessment And Cause Analysis Of Extreme Climate Change In The Upper And Middle Reaches Of Huai River Basin Based On CMIP6

In recent years,various climate disasters such as high temperature and drought,low temperature and freezing damage,and floods have occurred frequently worldwide,causing irreversible impacts on human production,life,and national economic and social development.The Huai River Basin is a transitional zone between the north and south climates of China,and also one of China’s granaries.It is an important geographical and ecologically sensitive area in China.In order to study the changes in extreme climate events within the watershed,this article uses extreme climate index and extreme threshold index,linear trend method,Mann Kendall test,Pearson correlation analysis method,based on meteorological data from 19 meteorological stations,CMIP6 model data,and atmospheric circulation data in the upper and middle reaches of the Huaihe River basin from 1960 to 2014 The optimal CMIP6 model within the watershed was selected using methods such as inverse distance weight interpolation,and the spatiotemporal variation characteristics of extreme climate events under historical and future scenarios were analyzed,as well as the causes of extreme climate events in the watershed.The main conclusions are as follows:(1)The preferred modes ACCESS-ESM1-5 and CMCC-ESM2 show consistent trends in simulated climate data over time with actual observation data;Through the spatial analysis of the actual historical climate data,it can be concluded that the model climate data can well simulate the spatial distribution characteristics of the annual average temperature of the basin,that is,the decrease from north to south,and the "fan" distribution pattern of the average precipitation,that is,the increase from south to north.(2)The spatial distribution of extreme low temperature threshold and extreme high temperature threshold within the watershed varies greatly from north to south;The threshold of extreme rainfall shows an increasing trend in spatial distribution from north to south.(3)The spatial variation trend of the extreme climate index in the watershed corresponds to the interannual variation trend,that is,the extreme warmth index,other indices,and extreme value index show an upward trend,while the cold index shows a downward trend,but the variation trend is basically the same in different regions;The spatial distribution of precipitation index shows significant differences.The sudden change in the extreme temperature index occurred before 2000,mainly between 1990 and 2000,while the sudden change in the extreme precipitation index occurred around 2000 and 2010.(4)From the perspective of time distribution,the daily maximum precipitation of the four emission scenarios shows an upward trend.From the perspective of spatial distribution,the three different emission scenarios on the four extreme climate indices are relatively consistent in spatial distribution,and the regions with the highest values are also relatively consistent,with slight differences in size changes.(5)There is a good correlation between the extreme climate threshold of the watershed and altitude,but it is not strongly correlated with longitude and latitude.The extreme precipitation indicators in the middle and upper reaches of the Huaihe River basin are not strongly correlated with longitude and latitude,but negatively correlated with altitude;The extreme temperature index that characterizes cold is negatively correlated with latitude and longitude,and positively correlated with altitude;The extreme temperature index,which represents warmth,is positively correlated with longitude,significantly negatively correlated with latitude,and weakly correlated with altitude.Among the selected atmospheric circulation factors,the correlation between Arctic Oscillation AO and the trend of extreme precipitation index in the basin is the best.The time trend of the extreme climate index in the Huaihe River Basin corresponds to the trend of regional extreme climate change across the country.The extreme temperature index and extreme precipitation index,which represent warmth,show an upward trend,while the extreme temperature index,which represent cold,shows a downward trend.This article provides theoretical support for water resource allocation in the Huai River Basin by studying extreme climate events and predicting the possibility of future extreme climate events,thereby promoting sustainable economic,social,and ecological development.This article provides theoretical support for water resource allocation in the Huai River Basin by studying extreme climate events and predicting the likelihood of future extreme climate events,thereby promoting sustainable economic,social,and environmental development.