A Basic Study on Soil Moisture Algorithm Using Ground-Based Observations Under Dry Condition

Abstract

Ground-based microwave radiometric field observations were conducted by using the Ground Based Passive Microwave Radiometer (GBMR) at frequencies of 6.9, 10.65 and 18.7 GHz to gain a better understanding of the physical mechanism of the radiative transfer process taken place in dry soil media. A metal plate was used as a bottom boundary and dry soil was put on it by increasing its depth one centimeter by one centimeter. The observed brightness temperature increased as the dry soil depth increased, while the increment of brightness temperature per one centimeter increase of soil depth was getting smaller. This behavior demonstrated the existence of volume scattering effects in the dry soil. Three models: surface emission model, Mie-scattering model and dense media radiative transfer model, were applied to the experiment results. The dense media radiative transfer model shows the best agreement with the observed data.