Numerical Simulation of the Full-Polarimetric Emissivity of Vines and Comparison with Experimental Data

Abstract

Surface soil moisture is a key variable needed to understand and predict the climate. L-band microwave radiometry seems to be the best technique to remotely measure the soil moisture content, since the influence of other effects such as surface roughness and vegetation is comparatively small. This work describes a numerical model developed to efficiently compute the four elements of the Stokes emission vector (T h , T v , T U and T V ) of vegetation-covered soils at low microwave frequencies, as well as the single-scattering albedo and the extinction coefficient of the vegetation layer over a wide range of incidence angles. A comparison with L-band (1.400-1.427 MHz) experimental radiometric data gathered during the SMOS REFLEX 2003 field experiment over vines is presented and discussed. The measured and simulated emissivities at vertical polarization agree very well. However, at horizontal polarization there is some disagreement introduced by the soil emission model. Important radiometric parameters, such as the albedo, the attenuation and the transmissivity are computed and analyzed in terms of their values and trends, as well as their dependence on the observation and scene parameters. It is found that the vegetation attenuation is mainly driven by the presence of branches and leaves, while the albedo is

First Polarimetric GNSS-R Measurements from a Stratospheric Flight over Boreal Forests

“…EMISVEG was originally developed for full-polarimetric microwave emission studies at L-band, but it has been now adapted to compute the forward scattering. L-band (1.400-1.427 MHz) data from the SMOS REFLEX 2004 field experiment [29] were used to validate the model. In the frame of this work, it has been modified to evaluate the forward scattering coefficient over boreal forests at circular polarization using the Forward Scattering Alignment (FSA) convention.…”

Generic Performance Simulator of Spaceborne GNSS-Reflectometer for Land Applications

“…The modelling of the vegetation effects could follow a very complex approach such as in [21,23,24], but the problem is finding the right input parameters to run the model. Therefore, a more pragmatic approach has been followed, inspired in the - model used in microwave radiometry at L-band [25].…”

“…Reflection/scattering geometry of the surface facet. The interested reader is referred to[21] for a detailed formulation of the equations to compute the above vectors and angles.…”

Contributions to GNSS-R earth remote sensing from nano-satellites

“…8.13a for high elevation angles in the range e θ = [60º, 70º], and in Fig. 8.13b for low elevation angles in the range e θ = [25º, 45º], showing that the relative weight is roughly independent of the flight height for a re-constructed scattered field corresponding to an along-track 31 of ~ 25 km.…”

“…The EMISVEG simulator was originally developed [29,30] to compute the polarimetric Stokes emission vector (the horizontal , and fourth V T Stokes parameters) of vegetationcovered soils at low microwave frequencies. A validation of the model with L-band (1,400-1,427 MHz) data from the SMOS REFLEX 2004 field experiment was performed [31]. In the frame of this work, it has been modified to evaluate the forward coherent reflectivity over boreal forests at L1 (1,575 MHz) at circular polarization following the Forward Scattering Alignment (FSA) convention.…”