Preliminary Analysis on the Relationships between NDVI Change and Its Temperature and Precipitation in Southwest China

Based on the monthly Normalized Difference Vegetation Index (NDVI) data that it is made by GIMMS (Global Inventory Modeling and Mapping Studies) workgroup of National Aeronautics and Space Administration (NASA) and the monthly mean air temperature, precipitation data from 96 stations in the Southwest China for the period of 1982 to 2001, the change characteristic of NDVI and the relationship between the NDVI and the air temperature, precipitation have been studied.The results are summarized as follows:In the last 20 years the vegetation cover is well over Southwest China.The NDVI in spring is best and the biggest regional differences is in winter.NDVI is mainly increased over all Southwest China.Meanwhile, There are significant regional and seasonal differences in there.NDVI is increased slightly in spring.It is mainly increased over all Region, especially sharp in south.In summer and autumn NDVI is basically decreased in Southwest China, 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.The time lag partial correlation between NDVI and temperature, precipitation show that the NDVI in November-February have a big sensitivity for temperature in September-January, the same complexion is NDVI in summer and temperature in spring, the precipitation in last summer plays an important role to the NDVI in March-April.In the meantime, NDVI has the best positive correlation with temperature in January to March and the best negative correlation with precipitation in June to September.When climate condition lag behind the NDVI, the NDVI in January to February not only has the best positive correlation with the temperature lags NDVI 1 to 2 months but also has the best negative correlation with precipitation lags NDVI 1 month.