Abstract:

The data at 33 meteorological stations in five southwestern provinces including Sichuan, Yunnan, Guangxi,Guizhou and Chongqing were used to analyze the spatiotemporal distribution of the extreme climate indices.The MK test and moving ttest methods were used to analyze the jump years and the trend of the extreme climate indices.GIS was used to draw the distribution maps.It was found that extreme precipitation indices except PRCPTOT and CDD in the five southwestern provinces showed a weak upward trend during the past 60 years; precipitation amount of the region decreased slightly,while the maximum daily precipitation amount and intensity of precipitation increased.It indicated that the total precipitation in the region decreased slightly,while the precipitation was more concentrated.It was confirmed by the increase of R95,Rx1d,Rx5d and SDII.The jump for most of extreme precipitation indices occurred in the 1990s,after that,the variation trend of extreme precipitation indices was obvious.Extreme air temperature indices including TN10,TX10 and DTR showed a downward trend,and other 7 indices all showed a upward trend,especially,the warm night index (TN90) and warm sustained days index (WSDI) significantly increased.It indicated that the five southwestern provinces have shown a warming trend,and diurnal temperature difference was smaller.At the spatial scale,extreme precipitation indices associated with precipitation in the five southwestern provinces showed an increasing trend from northwest to southeast.The high value and the low value region are easy to find.Those indices including total precipitation of wet day (PROPTOT),maximum daily precipitation and maximum fiveday precipitation showed a high value in Guangxi,Guizhou and Chongqing.It indicated that the precipitation amount here was more than other region and the precipitation was more centralized.Those indices showed a small value in Sichuan and part of the Yunnan province,and the continuous days of drought (CDD) showed a high value.Therefore,drought risk in these two provinces was higher,apart from the influence factor of topography and human activity.Spatial distribution of extreme air temperature indices was not significant.Cold extremes indicated that Yunnan Province showed the highest air temperature,and Guizhou Province showed the minimum air temperature.Warm extremes distribution map generally presented an increasing trend from west to east in the region.The two indices showed a high value in Guangxi and Chongqing,indicating a higher temperature.The rule of diurnal temperature range ( DTR ) distribution was obvious,western Sichuan and Yunnan had a much higher value than that in the eastern Chongqing,Guizhou and Guangxi.Maerkang station of Sichuan showed the highest value of DTR,up to 1601℃,Lancang station of Yunnanalso reached as high as 13℃.Warm sustained days index (WSDI) distribution was different with other indices,and it had no obvious regularity.Most areas of Yunnan province showed a high value,for example,the WSDI in Deqin station was up to 20 d.It was found that the risk of extreme climate events will be higher in Yunnan Province from our comprehensive analysis of extreme climate indices