辐射干燥指数影响下NDVI与气候因子的关系

在全球1o ×1o 分辨率格点数据的基础上研究了1986～1990年多年平均NOAA/AVHRR的归一化植被指数(NDVI) 与多年平均降水(Pcp)、多年平均净辐射量(NetRn)、多年平均辐射干燥指数(RDI) 之间的关系,结果表明:(1) NDVI与降水、辐射干燥指数总体上存在对数关系,NDVI与净辐射量总体上存在线性关系。(2) 在不同的辐射干燥指数下,NDVI与降水、净辐射的相关性存在很大的差异。当辐射干燥指数小于1时,ND-VI与降水、净辐射之间存在明显的非线性关系;当它大于1且小于2时,NDVI与降水的非线性关系略好于线性关系;当它大于2且小于10时,它们存在明显的线性关系;而当辐射干燥指数大于10时,它们之间的相关性很小。(3) 以全球13种植被为基础,分别研究了不同植被类型下的NDVI与降水、辐射干燥指数、净辐射量之间的关系,结果表明不同植被类型下的NDVI与这些气候因子的相关性不同,分层聚类的结果表明,这13种植被类型下的NDVI与降水、净辐射的关系可以分为4种类型。

The Relationship of NDVI and Climatic Factors under Different Radiation Dryness Indexes

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.