西南地区近21年来NDVI变化特征分析

Analysis of NDVI variation features over Southwest China during last 21 years

利用美国国家航天航空局（NASA）归一化植被指数（GIMMS NDVI）资料,初步分析了近21年（1982~2002）来西南地区植被变化特征。结果发现：21年来西南地区植被覆盖状况较好,总体呈增加趋势,同时也存在较明显的季节和区域差异：春季西南大部分地区植被呈较明显的增加趋势。夏季全区NDVI以显著的减小趋势为主,尤以90年代中期以后更为明显。秋季NDVI与夏季类似同样表现为减少趋势,并且范围有所增加。冬季ND-VI以增加为主,存在明显的东西反向特征,东部以减少为主,西部则以增加为主。

Based on the monthly Normalized Difference Vegetation Index（NDVI） data made by the GIMMS workgroup of NASA between 1982 and 2001 the variation features of NDVI over Southwest China are studied by using the methods of the empirical orthogonal function（EOF）,Correlation analysis et al.The results are summarized as follows：（1） During the last 21 years the vegetation cover is well and increased slowly over Southwest China.NDVI is increased in winter and spring and reduced in summer and autumn.The changed trend is obviously increased in spring and reduced in summer.（2） NDVI is mainly increased over all Southwest China.There are significant regional differences with the main feature opposite the change direction between the east and the3 west.It is reduced in east and increased in west mainly.（3） NDVI is increased slightly before 1995 and obviously later in spring.It is mainly increased over all Region,especially sharp in south.In summer NDVI is basically decreased in Southwest China,more obvious after the mid-1990s.The decreasing trend of NDVI in autumn is easier than summer but the scope is expanded.Winter NDVI is mainly increased over all Southwest China.There are significant regional differences with the main feature opposite the change direction between the east and the west.It is reduced in east and increased in west mainly.