. Baup, two different regression functions depending on the season, but 310 the data under consideration are restricted to those acquired at 311 an incidence angle lower than 30° in order to minimize soil 312 roughness and vegetation effects In this case, the number of 313 available data is about 1.2 samples per decade. At a 23° 314 incidence angle, model simulations, The third method indicate that the measured 317 backscatter originates from two main contributions, namely the 318 soil surface and the interaction between the soil and the 319 vegetation. These contributions are mainly driven by SSM 320 which controls the dielectric properties of the upper soil profile, pp.309-316, 1992.

. For, on surface backscattering coefficient 352 are taken into account by simply using a wet and a dry season 353 normalization function, as depicted in Fig. 6. This method does 354 not require any ancillary information on the vegetation status. 355 To further investigate the effect of vegetation on soil moisture 356 retrieval performance, seasonal features of the angular varia- 357 tions of the backscattering coefficient are addressed in this 358 subsection through the use of ancillary LAI information. For 359 each day, a sigma normalization function is interpolated 360 between the dry and wet curves, based on a linear weighting 361 function of the observed LAI. The corresponding date 362 normalization function is then applied for the N23_season 363 method, for which the whole ASAR data set is used whatever 364 the incidence angle is

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