Evaluation of the Effects of Heterogeneous Soil Moisture on Measured Brightness Temperature by a Microwave Radiometer

The spatial heterogeneity of ground within a passive microwave pixel has a considerable effect on measured brightness temperature. In this paper, two types of soil moisture distribution patterns, the ‘center’ pattern and the ‘matrix’ pattern, were set up in a controlled field experiment to be observed by a microwave radiometer. Soil moisture was changed artificially during the experiment to form different soil moisture distributions within the footprint. The brightness temperatures of varying soil moisture conditions were simulated by the area weighted method (AWM) and antenna gain pattern weighted method(APWM). The effects of heterogeneous soil moisture on observed brightness temperatures were explored by comparing the brightness temperatures between measured and simulated values. It has shown that the simulated brightness temperatures matched well with observed values for the ‘center’ pattern using AWM. In the ‘matrix’ pattern, however, the brightness temperatures calculated using APWM were more coincident with the observations comparing to values calculated by AWM.