Trend variations and spatial difference of extreme air temperature events in the Loess Plateau from 1965 to 2013
Based on daily temperature (average,maximum,and minimum) data from 52 meteorological stations,this study analyzed the spatiotemporal variation of 16 extreme air temperature events in the Loess Plateau from 1965 to 2013,using the methods of linear regression,Mann-Kendall test,correlation analysis,and Hurst index.The results are as follows:(1) From the view of temporal variation,the occurrence of ice days (ID0),frost days (FD0),cold days (TX10p),cold nights (TN10p),as well as the cold spell duration indicator (CSDI) and diurnal temperature range (DTR),indicated statistically significant decreasing trends (P ＜ 0.05).In particular TX10p clearly decreased (4.63d/10a,P ＜ 0.001),while the occurrence of tropical nights (TR20),summer days (SU25),warm days (TX90p),warm nights (TN90p),warm spell duration days (WSDI),and growing season length (GSL) had significantly increasing trends (P ＜ 0.05),of which TX90p had an especially clear increase (5.68d/10a,P ＜0.001).The monthly minimum value of daily maximum temperature (TXn),monthly minimum value of daily minimum temperature (TNn),monthly maximum value of daily maximum temperature (TXx),and monthly maximum value of daily minimum temperature (TNx) showed increasing trends of 0.30℃/10a,0.40℃/10a,0.20℃/10a,and 0.30℃/10a,respectively;(2) In terms of spatial distribution,the extreme warm indices (TR20,SU25,TX90p,TN90p,and GSL) indicated that extremely high temperatures had the most significant increasing trends in the north Loess Plateau region,and the cold indices (ID0,FD0,TX10p,TN10p,and CSDI) indicated that extremely low temperatures had the most significant decreasing trends in the northwest Loess Plateau region.GSL increased most significantly in areas located in the central Loess Plateau region;(3) Pearson correlation indicated that all the extreme air temperature indices had good correlation,except for the extremal indices (TXn,TNn,TXx,and TNx) and the diurnal temperature range;(4) There was a close correlation between the trends of the most extreme air temperature indices and average temperature,and poor correlation between the trends of the most extreme air temperatures and elevation.It was also shown that the abrupt change points of average temperature mainly occurred in 1991,and ID0,FD0,TX10p,TN10p,CSDI,and DTR showed a decreasing trend;(5) Results of Hurst index indicated that the warm indices would keep increasing,while the cold indices would continue to decrease.
extreme temperature indicestrend variationsspatial differenceLoess Plateau region
NETL
NSTL
万方数据
维普
