Field measurements of soil moisture in Tsukuba using microwave scatterometer

Abstract

The hydrological information at the large area are important to know the interaction between the land surface and the atmosphere. Now the microwave sensors mounted on satellites such as E ERS-1 and J ERS-1 are expected to collect the new information. This study will focus mainly on the relationship between the soil moisture and the backscattering coefficient measured by the microwave sensors. The backscattering coefficient value is affected not only by the soil moisture but also by other factors such as polarization, incident angle, sensor's frequency, surface roughness, soil composition etc.This paper examines effects of polarization and incident angles on the backscattering for two different experimental sites, using a C-band scatterometer system. In case of the bare soil, as the incident angle increases, the backscattering coefficient value decreases. As for the relationship between the soil moisture and the backscattering coefficient, as the incident angle increases, the soil moisture sensitivity increases while the correlation coefficient decreases. In the measurement of the soil moisture by the C-band scatterometer at FIELD, the better system combination is found to be the cross-polarization and the incident angles at 20°.