Applications of passive microwave observations of surface soil moisture

In large scale field experiments over the past 10 years, long wavelength microwave radiometers have been used to map surface soil moisture with considerable success. These experiments, which include PIPE (87 & 89), Monsoon 90, Washita 92 and 94, and HAPEX-Sahel, covered a wide range of climatic regimes. The results from all of them have shown that the microwave emission at the 21-cm wavelength is a strong function of surface (0 to 5-cm) soil moisture. The salient results from these experiments are presented and compared. The use of the surface soil moisture data to determine geophysical parameters such as evaporative fraction, soil evaporation and soil hydraulic properties are discussed