title: On the Soil Roughness Parameterization Problem in Soil Moisture Retrieval of Bare Surfaces from Synthetic Aperture Radar.
abstract: Synthetic Aperture Radar has shown its large potential for retrieving soil moisture maps at regional scales. However, since the backscattered signal is determined by several surface characteristics, the retrieval of soil moisture is an ill-posed problem when using single configuration imagery. Unless accurate surface roughness parameter values are available, retrieving soil moisture from radar backscatter usually provides inaccurate estimates. The characterization of soil roughness is not fully understood, and a large range of roughness parameter values can be obtained for the same surface when different measurement methodologies are used. In this paper, a literature review is made that summarizes the problems encountered when parameterizing soil roughness as well as the reported impact of the errors made on the retrieved soil moisture. A number of suggestions were made for resolving issues in roughness parameterization and studying the impact of these roughness problems on the soil moisture retrieval accuracy and scale.
authors.affiliation: Laboratory of Hydrology and Water Management, Ghent University, Coupure links 653, B-9000 Ghent, Belgium. niko.verhoest@ugent.be.
authors.forename: Niko E C
authors.initials: NE
authors.lastname: Verhoest
authors.affiliation: Laboratory of Hydrology and Water Management, Ghent University, Coupure links 653, B-9000 Ghent, Belgium. hans.lievens@ugent.be.
authors.forename: Hans
authors.initials: H
authors.lastname: Lievens
authors.affiliation: Christian Doppler Laboratory, Institute of Photogrammetry and Remote Sensing, Vienna University of Technology (TU Wien), Gusshausstraβe 27-29, 1040 Vienna, Austria. ww@ipf.tuwien.ac.at.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wagner
authors.affiliation: Department of Projects and Rural Engineering, Public University of Navarre, Los Tejos, Arrosadia s/n, 31006 Pamplona, Spain. jesus.alvarez@unavarra.es.
authors.forename: Jesús
authors.initials: J
authors.lastname: Álvarez-Mozos
authors.affiliation: USDA ARS Southwest Watershed Research Center, 2000 E. Allen Rd., Tucson AZ 85719, Arizona, USA. susan.moran@ars.usda.gov.
authors.forename: M Susan
authors.initials: MS
authors.lastname: Moran
authors.affiliation: Consiglo Nazionale delle Ricerche (CNR), Istituto di Studi sui Sistemi Intelligenti per l'Automazione (ISSIA), via Amendola 122/D, I-70126 Bari, Italy. mattia@ba.issia.cnr.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Mattia
keywords: Soil moisture retrieval; Soil roughness; Synthetic Aperture Radar; Uncertainty.