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Influence of Surface Roughness Spatial Variability and Temporal Dynamics on the Retrieval of Soil Moisture from SAR Observations
Department of Projects and Rural Engineering, Public University of Navarre, Los Tejos, Arrosadia s/n, 31006 Pamplona, Spain
Laboratory of Hydrology and Water Management, Ghent University, Coupure links 653, B-9000 Ghent, Belgium
Department of Territorial Information Systems, TRACASA, Cabárceno 6, 31621, Sarriguren, Spain
* Author to whom correspondence should be addressed.
Received: 19 November 2008; in revised form: 19 December 2008 / Accepted: 12 January 2009 / Published: 13 January 2009
Abstract: Radar-based surface soil moisture retrieval has been subject of intense research during the last decades. However, several difficulties hamper the operational estimation of soil moisture based on currently available spaceborne sensors. The main difficulty experienced so far results from the strong influence of other surface characteristics, mainly roughness, on the backscattering coefficient, which hinders the soil moisture inversion. This is especially true for single configuration observations where the solution to the surface backscattering problem is ill-posed. Over agricultural areas cultivated with winter cereal crops, roughness can be assumed to remain constant along the growing cycle allowing the use of simplified approaches that facilitate the estimation of the moisture content of soils. However, the field scale spatial variability and temporal variations of roughness can introduce errors in the estimation of soil moisture that are difficult to evaluate. The objective of this study is to assess the impact of roughness spatial variability and roughness temporal variations on the retrieval of soil moisture from radar observations. A series of laser profilometer measurements were performed over several fields in an experimental watershed from September 2004 to March 2005. The influence of the observed roughness variability and its temporal variations on the retrieval of soil moisture is studied using simulations performed with the Integral Equation Model, considering different sensor configurations. Results show that both field scale roughness spatial variability and its temporal variations are aspects that need to be taken into account, since they can introduce large errors on the retrieved soil moisture values.
Keywords: Synthetic Aperture Radar; Soil moisture retrieval; Surface roughness
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Álvarez-Mozos, J.; Verhoest, N.E.; Larrañaga, A.; Casalí, J.; González-Audícana, M. Influence of Surface Roughness Spatial Variability and Temporal Dynamics on the Retrieval of Soil Moisture from SAR Observations. Sensors 2009, 9, 463-489.
Álvarez-Mozos J, Verhoest NE, Larrañaga A, Casalí J, González-Audícana M. Influence of Surface Roughness Spatial Variability and Temporal Dynamics on the Retrieval of Soil Moisture from SAR Observations. Sensors. 2009; 9(1):463-489.
Álvarez-Mozos, Jesús; Verhoest, Niko E.; Larrañaga, Arantzazu; Casalí, Javier; González-Audícana, María. 2009. "Influence of Surface Roughness Spatial Variability and Temporal Dynamics on the Retrieval of Soil Moisture from SAR Observations." Sensors 9, no. 1: 463-489.