Spatial Distribution And Temporal Trends Of Extreme Temperature And Extreme Precipitation Over Beijing-Tianjin Sand Source Region

Based on daily temperature and precipitation records in the Beijing-Tianjin sand source region (BTSSR), the spatial and temporal distribution of mean temperature, mean precipitation, extreme temperature and extreme precipitation were analzed during 1960 to 2014. The MK trend test. Sen’s slope. Mean method and Least Squares regression were utilized to detect monotonic trends and magnitudes of general climatic factors and extreme climate index. The results obtained indicate:1. Both the mean temperature and the extremes have been warming; mean annual precipitation has decreased, while seasonal precipitation change differently:increase in spring and autumn, and decrease in summer and winter, and the extreme precipitation index in addition to SDⅡ have decreased. On an annual basis, the extreme temperature indices have significantly warmed except for TXx. RX1day、 RXSday and R99p have significantly decreased, while the other extreme precipitation indices do not change obviously which suggests that the precipitation decrease in the BTSSR is due to the decrease in both precipitation intensity and amount of extreme precipitation.2. In terms of spatial distribution, the annual mean temperature, spring and summer mean temperature rise in all stations in addition to Chengde, Hebei. Mean temperature in autumn and winter rise in all stations. And the rising rate of temperature is maximum in winter and minimum in summer, while the rising rate of temperature is similar in spring and autumn in the stations where temperature rose significantly. Regional annual precipitation, seasonal precipitation and extreme precipitation index show significant changes in a few stations. The annual precipitation reduce significantly at Wutaishan of Shanxi and Changling of Jilin. The spring precipitation show a significant upward trend in the stations locating in the southeast of the study area. The precipitation in summer decrease significantly in the central and southeastern part of the study area. Autumn precipitation increase significantly only in Wutaishan of Shanxi, and significantly reduce in Beijing. Winter precipitation show a significant increase in the stations locating in the southwest and northeast of the study area, but significantly reduced only in Wutaishan of Shanxi.3. The frequency of extreme precipitation(R10、R20、R25) has significantly decreased at Wutaishan of Shanxi、Ongniud Banner of Inner Mongolia、Huailai and Fengning of HeBei and Yinchuan of Ningxia, while significantly increased at Weixian of HeBei and Wuzhai of Shanxi. The extreme precipitation intensity(RX1day、RX5day、SDⅡ) has significantly decreased in the eastern part of the study area, while significantly increased at East Ujimain of Inner Mongolia, Xingxian and Yuanping of Shanxi. CWD has significantly shortened at Linxi and Xilin Hot of Inner Mongolia, Wutaishan of Shanxi and Weixian of HeBei; CDD has significantly shortened at Siziwang Banner, Mau Banner, Ulanhot and Kailu of Inner Mongolia, while significantly extended at Wutaishan of Shanxi and Huade of Inner Mongolia; the amount of extreme precipitation(R95p、R99p) has significantly decreased at Beijing, Huailai and Fengning of HeBei, Ongniud Banner、Hollyhock, Jartai and Baoguotu of Inner Mongolia and Changling of Jili, while significantly increased in Yinchuan of Ningxia. PRCPTOT has significantly decreased at Wutaishan of Shanxi and Changling of Jilin, which is similar to the spatial distribution of mean annual precipitation.