Effect of surface roughness on the microwave emission from soils

TLDR

The study introduces a single roughness parameter into the Fresnel reflection coefficient and validates it with truck‑mounted and airborne radiometer data. Model calculations show that the roughness parameter, which depends on height variance and horizontal scale, yields brightness temperature predictions that agree with observations and reveal up to a 50 K difference between smooth and rough wet soils.

Abstract

The effect of surface roughness on the brightness temperature of a moist terrain has been studied through the modification of Fresnel reflection coefficient and using the radiative transfer equation. The modification involves introduction of a single parameter to characterize the roughness. It is shown that this parameter depends on both the surface height variance and the horizontal scale of the roughness. Model calculations are in good quantitative agreement with the observed dependence of the brightness temperature on the moisture content in the surface layer. Data from truck mounted and airborne radiometers are presented for comparison. The results indicate that the roughness effects are great for wet soils where the difference between smooth and rough surfaces can be as great as 50K.