The Relationship of NDVI and Climatic Factors under Different Radiation Dryness Indexes
辐射干燥指数影响下NDVI与气候因子的关系

The global 1*1 degree grid data were used to analyse the relationship between NOAA/AVHRR NDVI and the climatic factors which include multi-year average precipitation (Pcp), multi-year averaged net radiation (Netrn), and multi-year average radiation dryness index (RDI) from 1986 to 1990. The results showed that: (1) There, as a whole, existed a logarithmic relationship between NDVI and RDI, Pcp; whereas NDVI and net radiation (Netrn) had a linear relationship. (2) The correlations of NDVI with precipitation and net radiation had great difference under different RDI scopes. When RDI was less than 1, there existed a nonlinear relationship between NDVI and precipitation and net radiation; when RDI was greater than 1 and less than 2, the nonlinear relationship of NDVI and precipitation was a little better than linear relationship; when RDI was greater than 2 and less than 10, they had an apparent linear relationship; when RDI was greater than 10, their correlations were rather weak. (3) Based on 13 global vegetation types, the correlations of NDVI and Pcp, Netrn, RDI were different in different vegetations. The hierarchical cluster analysis showed that the correlations of NDVI with Pcp and Netrn could be divided into 4 categories.