Effective roughness modelling as a tool for soil moisture retrieval from C- and L-band SAR
- 1Laboratory of Hydrology and Water Management, Ghent University, Coupure links 653, 9000 Ghent, Belgium
- 2Department of Applied Mathematics, Biometrics and Process Control, Ghent University, Coupure links 653, 9000 Ghent, Belgium
- 3Department of Environment and Agro-Biotechnologies, Public Research Centre Gabriel Lippmann, rue du Brill 41, 4422 Belvaux, Luxembourg
- 4Department of Projects and Rural Engineering, Public University of Navarre, Arrosadia s/n, 31006 Pamplona, Spain
Abstract. Soil moisture retrieval from Synthetic Aperture Radar (SAR) using state-of-the-art back\-scatter models is not fully operational at present, mainly due to difficulties involved in the parameterisation of soil surface roughness. Recently, increasing interest has been drawn to the use of calibrated or effective roughness parameters, as they circumvent issues known to the parameterisation of field-measured roughness. This paper analyses effective roughness parameters derived from C- and L-band SAR observations over a large number of agricultural seedbed sites in Europe. It shows that param\-eters may largely differ between SAR acquisitions, as they are related to the observed backscatter coefficients and variations in the local incidence angle. Therefore, a statistical model is developed that allows for estimating effective roughness parameters from microwave backscatter observations. Subsequently, these parameters can be propagated through the Integral Equation Model (IEM) for soil moisture retrieval. It is shown that fairly accurate soil moisture results are obtained both at C- and L-band, with an RMSE ranging between 4 vol% and 6.5 vol%.