SOME FEATURES OBSERVED BY THE L-BAND PUSH BROOM MICROWAVE RADIOMETER OVER THE KONZA PRAIRIE DURING 1985-1989

Airborne L-band radiometric measurements were conducted over the Konza Prairie near Manhattan, Kansas, in the summers of 1985, 1987, 1988, a nd 1989 to study the relationship among surface microwave emission, so il moisture, and vegetation cover. The annual surface treatments that were applied to the watersheds in the experimental area appeared to sh ow a significant impact on the surface microwave emission. A watershed that was burned every year showed a better sensitivity to soil moistu re variation than those burned less frequently. This feature persisted even though the radiometric measurements were made over those watersh eds that were burned in the same year. It was concluded that the burni ng process might not completely remove a thatch layer of efficient mic rowave absorption, which was developed through years of accumulation o f senescent vegetation. Results from the analysis of these radiometric data sets also suggest the need of an adequate estimation of vegetati on biomass in order to obtain a reliable retrieval of surface soil moi sture from L-band radiometric measurements. On the basis of the data a cquired from the 1987 and 1989 field campaigns, the push broom microwa ve radiometer (PBMR) measurements are likely to give errors of the ord er of +/-0.065 g/cm(3) in surface soil moisture estimation if there ar e no measurements of vegetation biomass. Measurements of vegetation bi omass to an accuracy of +/-0.46 kg/m(2) improve the corresponding PBMR estimation of surface soil moisture to an accuracy of +/-0.032 g/cm(3 ).