THE EFFECT OF SOIL TEXTURE IN SOIL MOISTURE RETRIEVAL FOR SPECULAR SCATTERING AT C-BAND

Abstract

The objective of this paper is to analyze the behavior of specular scattering for difierent soil texture flelds at various soil moisture (mv) and analyze the data to retrieve the soil moisture with minimizing the efiect of the soil texture. To study the soil texture efiect on specular scattering 10 difierent soil flelds were prepared on the basis of change in soil constituents (i.e., percentage of sand, silt and clay) and experiments were performed in both like polarizations (i.e., HH-polarization and V V -polarization) at various incidence angles (i.e., varying incidence angle from 25 - to 70 - in step of 5 - ). Angular response of specular scattering coe-cients (ae - in HH-polarization and ae - vv in V V -polarization) were analyzed for difierent soil texture flelds with varying soil moisture content whereas the surface roughness condition for all the observations were kept constant. The changes in specular scattering coe-cient values were observed with the change in soil texture flelds with moisture for both like polarizations. Further, copolarization ratio (P = ae - /ae -) study was performed and it was observed that the dependency of copolarization ratio for change in soil texture fleld at constant soil moisture is less prominent whereas the value of copolarization ratio is varying with variation of moisture content. This emphasizes that copolarization ratio may be minimizing the efiect of soil texture while observing the soil moisture on specular direction. Regression analysis is carried out to select the best suitable incidence angle for observing the moisture and texture at C-band in specular direction and 60 - incidence angle was found the best suitable incidence angle. An empirical relationship between P and mv was developed for the retrieval of mv and the obtained relationship gives a good agreement with observed mv. In addition, mv was also retrieved