Calibrating a soil water and energy budget model with remotely sensed data to obtain quantitative information about the soil

A soil water energy and transpiration model (SWEAT) coupled with a microwave emission model (MICRO-SWEAT) was used to predict the microwave brightness temperature of both bare and corn plots during a drying cycle. The predicted microwave brightness temperatures compared favorably to measurements made with an L band (21 cm, 1.4 GHz) passive microwave radiometer. In addition, SWEAT successfully modeled time series of soil water content and soil temperature. The modeled brightness temperature for the bare soil was most sensitive to the parameters describing the soil water retention and conductivity characteristics. These were predicted by varying each parameter in turn until there was a minimum between the measured and modeled brightness temperature. The predicted parameters were in agreement with the measured values to within the experimental error. The microwave brightness temperatures estimated for the corn soil were sensitive to the vegetation parameters as well as to the soil hydraulic properties.