Changes of NDVI and their relations with principal climatic factors in the Yarlung Zangbo River Basin

As an index denoting vegetation cover, NDVI is influenced by many climatic factors such as precipitation and average air temperature.In this paper,NDVI is calculated on the basis of waveband characteristic of NOAA/AVHRR data(National Oceanic Atmospheric Administration/Advanced Very High Resolution Radiometer) for the Yarlung Zangbo River Basin.Then,the spatio-temporal change of NDVI is analyzed.The basin's NDVI is in consistency with season from 2001 to 2003.High value zone of NDVI is mainly distributed in the lower reaches and part of the middle reaches.Meanwhile,point data of principal climatic factors(precipitation and average air temperature) are interpolated to spatial grid data with Kriging method consistent with NDVI based on DEM of the Yarlung Zangbo River Basin.Then,the relation of NDVI and precipitation or average air temperature is analyzed with F checking and two-sample variance test in the basin.The result is P=0,which shows that correlation analysis has higher confidence.The linear and logarithmic correlation of NDVI and precipitation or average air temperature is analyzed at confidence level of 0.05. The conclusion is that NDVI and precipitation and average air temperature in the basin vary with seasons and are closely correlated.The linear correlation coefficient of NDVI and precipitation is 0.8,and that of NDVI and average air temperature is about 0.77.And the logarithmic correlation coefficient of NDVI and precipitation is 0.71,and that of NDVI and average air temperature is 0.7.