Discipline of temporal and spatial variation of annual mean air temperature in arid and semiarid region in northwest China in the recent 46 years

Using the mean surface air temperature data over the years 1961 -2006 of 139 stations within China northwest arid and semi-arid area(CNASA) and methods of linear regression analysis,multinomial fitting,EOF, REOF,Mann - Kendall,Glide T-examination,wavelet analysis and power spectrum analysis etc.,we analyzed the response of the annual mean air temperature in the areas to climate warming.The result shows that(1) The warming rate of annual mean temperature in CNASA was 0.34/10a during the period of 46a.Except that the west part of Xinjiang and east Qinghai Plateau' s partial places have unremarkable increasing trend and some areas of Qinghai' s Henan State have remarkable decreasing tendency,the other great parts of region are remarkable warming and synchronistically respond to the globle warming.(2) The standard deviation of annual mean temperature distributes in non-uniform.Except the south boundary and south-eastern coastal region of China,Gansu area' s standard deviation is relative small and the stability of annual mean temperature' s interannual variation in the other greater parts of region is bad.(3) Inner Mongolia,Shaanxi,Gansu,Ningxia and the Tarim Basin are the areas where the temperature changes most sensitively.The degree of annual mean temperature variation' s uniformity is higher in the arid and semi-arid area.From the beginning of 1970s,the temperature was transformed from decrease to increase and there was a remarkable mutation of it in 1986.After that the temperature got into a more remarkably increasing period.The entire area' s first 10 hot years all appeared in 1990s and after that,and 90%of various subdistricts' anomalous hot year also appeared after 1990.The anomalous temperature change has about 5-year and 10-year cycles.According to above 15-year climate change level,the temperature tendency also occupies the high position.(4) Annual mean temperature variation has the regional differences.In Inner Mongolia -Xinjiang and Shaanxi - Gansu - Ningxia - Qinghai area,their north area' s temperature variation was as different as opposite from their south area' s.(5) Using the REOF method,we detailedly divided the area into 4 sub-areas:the north sub-area,the plateau sub-area,the south Xinjiang sub-area and east sub-area.The area' s annual mean temperature transition has the regional differences,the plateau and south Xinjiang sub-areas monotonously got warmer without any obvious transition,nevertheless the north sub-area' s warm-getting time was earlier about 5-year than that of low latitude' s east sub-area.The annual mean temperature' s mutation started firstly from the plateau sub-area, and then they successively were north sub-area,east sub-area and south Xinjiang sub-area.The plateau and north sub-areas' mutation was earlier 10-year than that of the south Xinjiang and east areas.