A VERIFICATION OF THE TRIANGLE METHOD FOR OBTAINING SURFACE SOIL-WATER CONTENT AND ENERGY FLUXES FROM REMOTE MEASUREMENTS OF THE NORMALIZEDDIFFERENCE VEGETATION INDEX (NDVI) AND SURFACE RADIANT TEMPERATURE

An inversion procedure is presented for estimating surface soil water content (as surface moisture availability, M-o), fractional vegetation cover (Fr), and the instantaneous surface energy fluxes, using remote multispectral measurements made from an aircraft. The remotely derive d values of these fluxes and the soil water content are compared with field measurements from two intensive field measurement programs-FIFE and MONSOON '90. The measurements from the NS001 multispectral radiome ter were reduced to fractional vegetation cover, surface soil water co ntent (surface moisture availability), and turbulent energy fluxes, wi th the application of a soil vegetation atmosphere transfer (SVAT) mod el. A further step in the inversion process involved 'stretching' the SVAT results between pre-determined boundaries of the distribution of normalized difference vegetation index (NDVI) and surface radiant temp erature (T-o). Comparisons with measurements at a number of sites from two field experiments show standard errors, between derived and measu red fluxes, generally between 25 and 55 Wm(-2), or about 10-30 per cen t of the magnitude of the fluxes and for surface moisture availability of 16 per cent.