Effect of Antireflective Surface at the Radiobrightness Observations for the Topsoil Covered with Coniferous Litter

摘要

In radio thermal remote sensing of the land, a spot on the earth surface emitting the signal received by the microwave radiometer antenna may be partially or completely covered by forest. We developed a theoretical model to calculate radiobrightness of the layered topsoil. Using this model we derived the dielectric constants pertaining to the separate layers of topsoil. For this purpose, we applied the least squares method for fitting the calculated diurnal radiobrightness dependences to those measured. The forest soil covered with coniferous litter was modeled by a three steps dielectric profile, the interfaces between the separate layers being smooth. The theoretical modeling conducted confirmed that, at the moments of maximal radiobrightness, an antireflective layer was formed on the topsoil surface, most probably due to nonisothermal upward moving of soil moisture. At that, the theoretically calculated dielectric constant of the litter antirefiecting layer was found to be on the same order as the value measured in laboratory conditions.