REMOTE ESTIMATION OF SOIL-MOISTURE AVAILABILITY AND FRACTIONAL VEGETATION COVER FOR AGRICULTURAL FIELDS

The purpose of this paper is to present a method for using remote measurements to estimate vegetation fraction, surface energy fluxes and the root zone and soil surface water contents for partial vegetation canopies. The primary tools are a boundary layer model with vegetation and substrate components and two image products: the variation of surface radiometric temperature vs. normalized difference vegetation index (NDVI), and the standard deviation of radiometric surface temperature vs. radiometric surface temperature. The method is based on determining: (1) asymptotic values of two radiometric surface temperatures for sunlit bare soil and for dense sunlit vegetation; and (2) a relationship between NDVI and surface temperature, which we call the axis of variation. The method is illustrated using aircraft and surface measurements made at Lubbon during the French HAPEX field experiment (1986). © 1990.