Sk. Srivastava et al., INTERLINKAGES OF NOAA AVHRR DERIVED INTEGRATED NDVI TO SEASONAL PRECIPITATION AND TRANSPIRATION IN DRYLAND TROPICS/, International journal of remote sensing, 18(14), 1997, pp. 2931-2952
The NOAA/AVHRR derived Normalized Difference Vegetation Index (NDVI) o
ffers immense potential to study dryland ecosystems. Its relation with
rainfall in semi-arid regions is both sensitive and complex. The phys
ical basis of this relation is vegetation, mainly grown due to soil mo
isture availability as the result of the seasonal rainfall, which inte
rcepts photosynthetically active radiation (PAR) and hence directly in
fluences the aggregate of NDVI. While the major part of rainfall is lo
st through direct evaporation from the soil surface, run-off and drain
age, a small fraction of rain water which is used by crops for their g
rowth and yield, is a key parameter linking rainfall with NDVI, especi
ally in dryland tropics. The extent of non-utilized rain water depends
not only on the local weather parameters but also on optimal land and
water management practices along with the cropping pattern having eff
icient radiation use efficiencies. Although there have been several st
udies reporting the relation between AVHRR NDVI and rainfall in semi-a
rid regions the sensitivity of this relation in varying dryland condit
ions has rarely been analysed quantitatively. The present study aims t
o interpret seasonal AVHRR NDVI variations with the seasonal aggregate
of rainfall and fraction of soil moisture used by vegetation in the s
ix drought prone districts of Karnataka State, India representing very
severe, severe and moderate drought conditions. Area averaged seasona
l transpiration which has been theoretically linked to integrated NDVI
(INDVI), has been realized up to a certain extent in the study areas.
The study reveals a closer AVHRR NDVI relation with the water used by
vegetation for its growth and yield than the precipitation in dryland
ecosystems.