Modeling Diurnal Changes in Microwave Emission from Bare Soil

A radiative transfer model is applied to data collected in a bare agricultural field in order to determine the usefulness of the method. Both measured and simulated soil moisture and soil temperature profiles are used as the inputs to the radiative transfer model. The simulation is carried out through a land surface model called The Atmosphere and Land-surface Exchange model (ALEX). It is observed that ALEX outputs are in close agreement with the measured soil moisture and soil temperature variations. The radiative transfer model can reproduce the brightness temperature variation in time when the soil moisture and temperature do not change abruptly. However, in the case of an abrupt change, the model fails to reproduce the brightness temperature profile. One possible reason is that the model assumes a uniform soil in terms of the volumetric water content while the abrupt change in the measured brightness temperature could be due to the existence of layers that have different water contents. We hypothesize that a model that can account for a non-uniform soil water content must be used.