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Remote Sens. 2018, 10(4), 582; https://doi.org/10.3390/rs10040582

Impact of Surface Soil Moisture Variations on Radar Altimetry Echoes at Ku and Ka Bands in Semi-Arid Areas

1
Office National d’Etudes et de Recherches Aerospatiales (ONERA), 2 Avenue Edouard Belin, 31055 Toulouse CEDEX 4, France
2
Geosciences Environnement Toulouse (GET), UMR 5563, CNRS/IRD/UPS, Observatoire Midi-Pyrenees 8 (OMP), 14 Avenue Edouard Belin, 31400 Toulouse, France
3
Laboratoire d’Etudes en Geophysique et Oceanographie Spatiales (LEGOS), UMR 5566, CNRS/IRD/UPS, Observatoire Midi-Pyrenees 8 (OMP), 14 Avenue Edouard Belin, 31400 Toulouse, France
4
Centre National d’Etudes Spatiales (CNES), 18 Avenue Edouard Belin, 31400 Toulouse, France
*
Author to whom correspondence should be addressed.
Received: 28 February 2018 / Revised: 28 March 2018 / Accepted: 3 April 2018 / Published: 9 April 2018
(This article belongs to the Special Issue Satellite Altimetry for Earth Sciences)
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Abstract

Radar altimetry provides information on the topography of the Earth surface. It is commonly used for the monitoring not only sea surface height but also ice sheets topography and inland water levels. The radar altimetry backscattering coefficient, which depends on surface roughness and water content, can be related to surface properties such as surface soil moisture content. In this study, the influence of surface soil moisture on the radar altimetry echo and backscattering coefficient is analyzed over semi-arid areas. A semi-empirical model of the soil’s complex dielectric permittivity that takes into account that small-scale roughness and large-scale topography was developed to simulate the radar echoes. It was validated using waveforms acquired at Ku and Ka-bands by ENVISAT RA-2 and SARAL AltiKa respectively over several sites in Mali. Correlation coefficients ranging from 0.66 to 0.94 at Ku-band and from 0.27 to 0.96 at Ka-band were found. The increase in surface soil moisture from 0.02 to 0.4 (i.e., the typical range of variations in semi-arid areas) increase the backscattering from 10 to 15 dB between the core of the dry and the maximum of the rainy seasons. View Full-Text
Keywords: radar altimetry; waveform; dielectric permittivity; soil moisture radar altimetry; waveform; dielectric permittivity; soil moisture
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Fatras, C.; Borderies, P.; Frappart, F.; Mougin, E.; Blumstein, D.; Niño, F. Impact of Surface Soil Moisture Variations on Radar Altimetry Echoes at Ku and Ka Bands in Semi-Arid Areas. Remote Sens. 2018, 10, 582.

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