Radar altimetry backscattering signatures at Ka, Ku, C, and S bands over West Africa

Frédéric Frappart (1, 2) , C. Fatras (1, 3) , Éric Mougin (1) , V. Marieu (4) , A.T. Diepkilé (5) , F. Blarel (2) , P. Borderies (3)

1 GET - Géosciences Environnement Toulouse
2 LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales
3 ONERA - The French Aerospace Lab [Toulouse]
4 EPOC - Environnements et Paléoenvironnements OCéaniques
5 USTTB - Université des Sciences, des Techniques et des Technologies de Bamako

This study presents a comprehensive comparison of radar altimetry signatures at Ka-, Ku-, C-, and S-bands using SARAL, ENVISAT and Jason-2 data over the major bioclimatic zones, soil and vegetation types encountered in West-Africa, with an emphasis on the new information at Ka-band provided by the recently launched SARAL–Altika mission. Spatio-temporal variations of the radar altimetry responses were related to changes in surface roughness, land cover and soil wetness. Analysis of time series of backscattering coefficients along the West African bioclimatic gradient shows that radar echoes at nadir incidence are well correlated to soil moisture in semi-arid savannah environments. Radar altimeters are able to detect the presence of water even under a dense canopy cover at all frequencies. But only measurements at Ka-band are able to penetrate underneath the canopy of non-inundated tropical evergreen forests.

Mots clés: RADAR ALTIMETRY; SURFACE PROPERTIES; WEST AFRICA; BACKSCATTERING

Domaines: Géophysique [physics.geo-ph]; Ingénierie de l'environnement

Frédéric Frappart, C. Fatras, Éric Mougin, V. Marieu, A.T. Diepkilé, et al.. Radar altimetry backscattering signatures at Ka, Ku, C, and S bands over West Africa. Physics and Chemistry of the Earth. Parts A/B/C, 2015, 83-84, pp.96-110. ⟨10.1016/j.pce.2015.05.001⟩. ⟨hal-01414511⟩