Inter-annual variability of vegetation cover and rainfall over india Original Research Article

Normalized Difference Vegetation Index (NDVI) is a measure of vegetation cover and biomass. NDVI is being used as an indicator for primary productivity and crop yield, and is considered as an important biophysical input for global climate modeling. Seasonal dynamics of NDVI and rainfall is found to be apparent from percent deviation from long term average NDVI and rainfall. Efforts have been made to assess co-variability of NDVI and rainfall for dry and wet seasons. Average NDVI and rainfall for 10 years 1990–1999 have been used as base for percent variation in individual years separately for monsoon and non-monsoon periods. Rainfall and NDVI percent deviation from their respective average show positive correlation especially for monsoon season. Magnitude of co-variation differs from region to region. EOF and wavelet decomposition have been used to study the variability of NDVI with respect to rainfall over Indian region and also for different agro-climatic regions. Five principal modes, which explain about 70% of the total variance, have been identified. The first mode explains the major distribution of vegetation that is very much controlled by the monsoon rainfall and also dependent on the increasing pollution in recent years. The first and fourth modes are seen to be significantly correlated with the first mode of regional aerosol cover. ENSO and other tele-connection events fail to explain large variance of vegetation over the Indian sub-continent and local dynamics is found to be of more importance. The percent deviation and average greenness information and their temporal variations can be used in the assessment of drought prone regions.