INVERSION OF SURFACE PARAMETERS FROM PASSIVE MICROWAVE MEASUREMENTS OVER A SOYBEAN FIELD

Microwave emission from a soybean field was measured using a multifrequency radiometer: PORTOS. The experiment was conducted throughout the growing season. The acquired data are used in this study to assess how passive microwave measurements could be used to estimate land surface parameters. To this end, a method of inversion of remotely sensed data using a random continuous model was developed. Both soil moisture and biomass, parameterized by the vegetation volume fraction, appear to have very significant effect on the evolution of the microwave signal. Using different polarization and frequency (1.4 GHz, 5.05 GHz, and 36.5 GHz) configurations of the radiometer, the estimation of these two parameters is discussed. When monitoring biomass increase by PORTOS, saturation of the microwave signal appears at 5.05 GHz and 36.5 GHz, whereas the 1.4 GHz signal goes on increasing. Soil moisture was well retrieved at 1.4 GHz and 5.05 GHz throughout the growing season. The results of this study should improve both the interpretation of passive remotely sensed data over vegetated areas and the use of continuous modeling for inversion algorithms of land surface parameters.