Spatio-Temporal Variability Of Climate Extreme Events During 1957-2017 In The Sub-Regions Of The Belt And Road,China

Against the backdrop of global warming,the frequency of extreme weather events has increased,causing great impact on regional ecology,socio-economics and sustainable development.As an important part of the "Belt and Road",the regions along China’s "Belt and Road" are very sensitive to global climate change.In order to study the trends and spatial and temporal patterns of extreme climate events along the "Belt and Road" in China.Based on the daily maximum temperature,minimum temperature and daily precipitation data from 1957-2017 at national meteorological stations,this paper analyzes the spatial and temporal changes of extreme climate events along the "Belt and Road" region of China by using trend analysis,M-K mutation test,correlation analysis,wavelet analysis and R/S analysis,and The spatial and temporal variability of extreme climate events along the "Belt and Road" in China was investigated.The following conclusions are drawn.(1)In the past 60 a,the trend of annual average temperature along the "Belt and Road" in China has changed from "cold" to "warm",and the temperature has been rising.The trend of annual average precipitation is changing from "dry" to "wet",and the precipitation is increasing.(2)In terms of temporal changes,the extreme cold event indices all show a significant decreasing trend,while the extreme warm event indices all show a significant increasing trend,the extreme warm temperature indices all show an increasing trend,and in the extreme precipitation events all indices show a significant increasing trend.(3)In terms of spatial variation,the extreme cold index shows a significant decreasing trend along the "Belt and Road",with the western line showing a faster decreasing rate than the other three lines in space.The warm extreme temperature index shows a significant upward trend,with the northern and western lines increasing at a faster rate.The extreme precipitation indices show significant spatial differences,except for the number of continuous wet days(CDD)and extreme precipitation(R95),all the indices show an increasing trend from west to east.(4)All extreme warm indices showed significant positive correlation with each other,all extreme cold indices also showed significant positive correlation with each other,and all warm indices showed significant negative correlation with cold indices.The cold index and the annual mean temperature all showed significant negative correlation,the warm index and the annual mean temperature showed significant positive correlation,and the extreme warm index and the annual mean temperature showed significant positive correlation.The extreme precipitation indices were all positively correlated with the mean annual precipitation,and all the extreme precipitation indices showed highly significant positive correlations with each other.(5)The warm index is generally positively correlated with latitude and the cold index is negatively correlated with longitude along the "Belt and Road" in China.The extreme precipitation index is positively correlated with latitude and negatively correlated with longitude.In the northern route,except for TN90 P and TXx indices,which showed positive correlation with altitude,all other indices showed negative correlation effect with altitude.Due to the higher elevation in the west than in the east,the effect on the change rate of extreme precipitation indices is greater at higher elevations than at lower elevations.The atmospheric circulation index AO shows a negative correlation with the cold index and a positive correlation with the warm index.The atmospheric circulation PDO index showed a significant negative correlation with the continuous drought index and a significant positive correlation with the extreme precipitation index.(6)In terms of future trend changes,the future extreme temperature indices all show an increasing trend in the overall rise.The frequency of warm events is more significant compared to the frequency of cold events.Future extreme precipitation and extreme precipitation intensity both show an increasing trend in the overall rise.The frequency of extreme precipitation events is more significant.