Climate Changes Under Global Warming And Its Influence On Desertification Over The Qinghai-Tibet Plateau

Based on the daily data of 81 stations over the Qinghai-Tibet plateau form 1971 to 2011,using the area weighted method to analysis the climate change over plateau for the recent 41a. The spatial and temporal variation characteristics of vegetation cover condition over plateau is studied employ the NDVI data form 1982 to 2006, supplied by NOAA series of satellites, and combine with the climate, given a standard according to the NDVI maximum value to determine the desertification, and has explored the plateau desertification trend in recent years. In addition, the influence of plateau climate change on desertification has been researched. The results show that:(1)The Qinghai-Tibet plateau has warmed for recent years, and has a warm mutation in the late 1990s, and significant differences exist in the form of warming around the mutation, before the mutation, the magnitude of warming increases with altitude weakened, but after, it shows opposite change, the higher the altitude the greater the increase in the magnitude of warming. The Warm mutations interior plateau has obvious relationship with altitude, the higher the altitude, the later mutations, and lag behind the other area in China. Compared with the slowdown of global warming for recent 15 years, plateau after mutation showed more substantial warming.(2)Plateau rainfall increased significantly also, and exist a Northeast-southwest ribbon which precipitation increased great. The precipitation increase also has obvious relationship with altitude:rainfall increased more in higher altitude. The significant regional differences of precipitation may caused by the topographic and thermal adaptation effect.(3)The late 1990s is an important period of climate change over the Plateau, various meteorological elements have changed in this period. The dry and wet climate boundary and area have obvious decadal fluctuation, for recent 41 years, the overall performance of the plateau is:the area of extreme drought and drought has reduced, but the semiarid region, semi-humid areas and humid area has increased, and the wet area has largest increase.(4)It’s more reasonable to use the NDVI maximum value to measure the overall distribution of vegetation and explore the desertification situation over plateau. Combined with previous studies and fieldwork, given the type of land criteria:when NDVImax≤0.1,the point is non vegetation area; when 0.1<NDVImax≤0.3,the point is sparse vegetation, there may desertification; when NDVI>0.3,indicates that the point of lush vegetation, there is no possibility of desertification.(5)On condition(4),explore the the desertification development status, and finds that before the middle of 1990s, the desertification has developed, and after that, desertification area has reduced, it means the trend has reversed.Meteorological factors affecting vegetation in desertification area (sparse vegetation) are differences: the influence of precipitation to vegetation has hysteresis, temperature, sunshine to the same period more significant influence. Correlation analysis finds that the desertification area over plateau could be divided to seven part, and each suffer different effects.