Analysis and Evaluation of principal climatic factors of NDVI in the Yarlung Zangbo River Basin

The normalized difference vegetation index (NDVI) of vegetation covers is influenced by many climatic factors such as precipitation and average temperature. In this paper, NDVI is calculated on the basis of waveband characteristic of NOAA/AVHRR data for the Yarlung Zangbo River Basin. Then, the spatial-temporal change of NDVI is analyzed. The basin's NDVI is in consistency with season from 2011 to 2013.Large value zone of NDVI is mainly distributed in the lower reaches and part of the middle reaches. Meanwhile, point-data of principal climatic factors 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 precipitation and normalized difference vegetation indexes 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 larger confidence. The linear and logarithmic correlation of precipitation and normalized difference vegetation indexes or average air temperature is analyzed at confidence level of 0.05. The conclusion is that precipitation and normalized difference vegetation indexes and average air temperature in the basin vary with seasons and are closely correlated. The linear correlation coefficient of precipitation and normalized difference vegetation indexes is 0.8, and that of NDVI and average air temperature is about 0.77.And the logarithmic correlation coefficient of precipitation and normalized difference vegetation indexes is 0.71, and that of NDVI and average air temperature is 0.7.