Analysis On The Characteristics Of Temporal And Spatial Changes Of Extreme Climate Events In Qinba Mountains In The Past 42 Years

Qinling-Daba mountains region is the transitional zone between north and south located in the middle of China.Based on the daily temperature and precipitation data of 88 meteorological stations in the Qinling-Daba mountains from 1975 to 2016 and the 27 extreme climate indices,spatial heterogeneity of extreme temperature and precipitation events were analyzed Using trend change,linear fitting,correlation analysis,M-K mutation test and other methods in the Qinling-Daba mountains region.The results show that :(1)There is a significant spatial distribution difference in extreme temperature thresholds.The extreme low temperature threshold decreases from northwest to southeast,and has a significant positive correlation with altitude;The extreme high temperature threshold is opposite,showing an increase from northwest to southeast,and has a significant negative correlation with altitude.(2)The spatial distribution of extreme precipitation thresholds are significantly different,both showing that the extreme precipitation threshold is lower in the high elevation areas of the western part and the precipitation thresholds are higher in the south and the middle Qinling-Daba mountains.There is a significant negative correlation between the extreme precipitation threshold and altitude.(3)In the extreme temperature events,the warming events(SU25,TR20,TX90 P,TN90P,and WSDI)had a greater change than the cold events(FD0,ID0,TX10 P,TN10P,CSDI).In the extreme precipitation events,the consecutive dry days decreased significantly,passing a 99% significance test.(4)In terms of spatial distribution,the number of frost days,cold days,summer days,warm days,and high temperature extremes(TXx,TXn)in the whole area are all significantly higher.The warm days,warm nights,and growing season length in the western regions were all significantly higher than those in the eastern region.(5)92% of the stations in the region had a continuous decrease in the number of dry days,and 52% of them changed significantly.The consecutive dry days in the Qinling-Daba mountains is mainly reduced in the western region,while in the eastern region it is mainly showing an increasing trend.(6)The extreme temperature events have obvious mutations,and the year of their mutations is slightly different.The trends of extreme precipitation events are basically similar and have obvious characteristics of periodic changes.(7)Most of the extreme temperature events have an elevation-dependent trend,and the cold events are negatively correlated with the altitude.Among them,the change of the frost days is most significantly;There is a positive correlation with altitude which the warm days increases with altitude.In the extreme precipitation events,the 20 mm precipitation days,the consecutive dry days,and the consecutive wet days were negatively correlated with the altitude.