2.5.3 Land applications:
Monitoring continental surfaces

At a global scale, the backscatter coefficient values mainly ranges from 0 to 20 dB in S-band. The backscatter coefficient is high (~20 dB and more) on very flat surfaces: deserts, river basins or wetlands due to the specularity of the return echo. But it is low over mountainous regions. Strong variations can be seen, especially for regions which are covered by snow in winter or with a contrasted rainy season.
The backscattering coefficient results from a surface scattering echo and a volume scattering echo inside a medium. Over land surfaces, three different cases can be described:

• the return signal is only due to the surface echo: water surfaces, inundated soils, melting snow,
• the return signal is due to reflecting surfaces located under volumetric scatterers: sparse forests, inundated forests, dry snow,
• the return signal is due to reflecting surfaces located above volumetric scatterers: dry or arid areas, wet snow