Research On Temporal Evolution And Spatial Pattern In The Desert Region Of Northern China

The desert region of northern China is mainly located in the northwest inland river basin, the Yellow River Basin and the Inner Mongolia plateau ,where are the arid and semi-arid areas. Political district belongs to Xinjiang,Qinghai, Gansu, Inner Mongolia, Ningxia, Shaanxi, Shanxi and Hebei. The area is about 3.4 million square kilometers, accounting for 35% of the China. The precipitation is lack and uneven for the temporal and spatial distribution in the desert region of northern China. Unsuitable water and land resources exploitation led to ecological and environmental degradation sharply in this regions, which also is the main dust source of the northern China and the northeast Asian. The ecological and environmental construction are the major problems of the socio-economic sustainable development in this regions. Research on spatial and temporal variability of precipitation characteristics and trend in desert region have an important guiding significance, which can protection and restoration the vegetation of desertification and degraded ecosystem, promote regional socio- economic and ecological environment harmonious development.Spatial variability rule of precipitation and its trends of rich and lack are analysed in this paper by the monthly precipitation data of 35 national meteorological observation sites in the desert region of northern China during 1951- 2005. The temporal and spatial variability characteristics of the precipitation are discussed for the mountain-oasis-desert system (MODS) in arid region of northwest inland watershed,based on the observation data from the precipitation observation network located in the San-gong River watershed and established by Fukang National Desert Ecosystem Research Station,Chinese Academy of Sciences. Main results indicate as below:1. Spatial and temporal variability of precipitation in the desert region of northern China. In recent 50 years, the precipitation has greater variability both in spatial and temporal. It is estimated that the precipitation will increase in spring and summer season, and will decrease in winter sesson in future. Annual precipitation is increase in general. The areas which have bigger annual increased amplitude will move from east of the Inner Mongolia Plateau to northwest of China.There are 5a, 9a and 14a main-cycle, and the abrupt precipitation changes were observed in 1963,1988,1996 and 2000. Precipitation primarily controlled by 9a and 14a cycle since 1988. Precipitation spatial distribution pattern is primarily " complex type " and "west-east type " (to contribution the overall changes rates were 35.8% and 20.4%). Xinjiang is the best affected region for the precipitation fluctuations of the northern desert region (contribution to 70.4% of all fluctuations). The region characterized by " Complex type " has a greater impact by the local weather systems. " West-east type " shows that precipitation fluctuation trends were weakened from west to east. It is possible that the west region will bacome warmer and weter, the central region will bacome warmer and drier, but the eastern region will get drought.2.The trends for spatial and temporal variability of precipitation in the desert region of northern China. The probability of single abundant precipitation year is higher than single short precipitation year and the continuous short precipitation year is higher than continuous abundant precipitation year. In extreme arid regions and arid regions, such as Xinjiang,Qinhai and Gansu, the probability of precipitation increasing are 83% and 70 % respectively.On the contrary, in semi-arid regions,like Inn Mongolia, the probability of precipitation decreasing is 58%, the variability will change slowly for the distribution of intra-annual precipitation . The inter-annual precipitation variability has increasing trend in the western and eastern part of the northern desert region, but the central region change slowly, the scope is 15% to 78%, especially in south of Xinjiang and Qinghai, the inter-annual change is the biggest.In most regions, variation coefficient is more than 40%.The Inner Mongolia region is stable comparatively, about 28%.3.The precipitation spatial variation of MODS in inland river watershed. Based on the empirical orthogonal function (EOF) ,rotated empirical orthogonal function (REOF) and geostatistics methods, the precipitation observation network data of the San-gong River Watershed are analysed. The results showed that: based on the 0-30 km ,30-60km and 60-150 km of the three loads section, the watershed can be divided into three landscape units: mountain, oasis and desert. Precipitation increasing trend become smaller and smaller from mountain, oasis to desert. The mountain precipitation semivariogram accord gaussian model, the oasis precipitation semivariogram accord spherical model, the desert precipitation semivariogram model is different in each month .In research scale, owing to the random factors arising precipitation spatial heterogeneity occupy 0% -9.57% of all, so the spatial heterogeneity of spatial was mainly caused by autocorrelation. Based on all parts and periods of characteristic parameter, such as sill, fractal dimension and separation distance, it is judged that the biggest spatial variation of precipitation is in oasis,followed by mountain, desert area is minimum.The precipitation spatial aeolotropy is not remarkable in each landscape unit. For the whole watershed, precipitation spatial heterogeneity are the most significant in June, and the smallest in August, which coincides with the coefficient of variation.The precipitation variability in the north-south direction (0°) and the southeast-northwest (135°) are strongest.