Inversion Algorithm of Surface Roughness Effect for the Soil Moisture Measurement Using Active Microwave Remote Sensing.

Abstract

Quantitative evaluation of the surface roughness is a key to detect the surface soil moisture from the active microwave remote sensing. This study develops a new inversion algorithm of the surface roughness from a viewpoint of the hydrological application. Field experiments were conducted using C-band scatterometer system mounted on a car and the backscatter from the bare soil surface was observed with multiple angles at the same time. Measured surface roughness parameters vary and are very difficult to determine the representative roughness parameters even in a single field. The inversely obtained ones with the assumption that the soil moisture is known, does not agree with the measured ones, but the dependency of the backscattering coefficients computed from the theoretical model with the inversely obtained parameters, on both the incident angle and the soil moisture, shows good agreement with the observed ones. The result can be explained theoretically and terminology "surface roughness factor" is proposed to evaluate the surface roughnesses quantitatively.keywords: microwave backscatter, surface roughness, soil moisture, multi-angular