Diurnal Difference Vegetation Water Content (ddVWC) of Advance Microwave Scanning Radiometer-Earth Observing System (AMSR-E) for assessment of crop water stress at regional level
Advance Microwave Scanning Radiometer – Earth Observing System (AMSR-E) derived Vegetation Water Content (VWC) at predawn (01:30 LST, descending pass) and afternoon (13:30 LST; ascending pass) were used to assess crop water stress condition over the selected meteorological subdivisions of India. The temporal profile of Normalized Difference Vegetation Index (NDVI) was used to study the progression of crop growth. The Diurnal Difference Vegetation Water Content (ddVWC) was found to be sensitive to rainfall patterns (wet/dry spell) particularly in moderate to full crop cover condition (NDVI > 0.4). The ddVWC was found to be significantly (p = 0.05) correlated with the rainfall over the rainfed regions. The ddVWC was further characterized to represent different categories of crop water stress considering irrigated flooded rice crop as a benchmark. Inter year comparative analysis of temporal variations of the ddVWC revealed its capability to differentiate normal (2005) and sub-normal years (2008 and 2009) in term of intensity and persistence of crop water stress. Spatio-temporal patterns of ddVWC could capture regional progression of crop water stress at high temporal resolution in near real time.