ARS | Publication request: On the soil roughness parameterization problem in soil moisture retrieval of bare surfaces from Synthetic Aperture Radar 1959

Submitted to: Sensors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 7, 2008
Publication Date: July 15, 2008
Citation: Verhoest Niko, E.C., Lievens, H., Wagner, W., Alverez-Mozos, J., Moran, M.S., Mattia, F. 2008. On the soil roughness parameterization problem in soil moisture retrieval of bare surfaces from Synthetic Aperture Radar. Sensors. 2008. 8:4213-4248. DOI: 10.3390/s8074213.

Interpretive Summary: Regional maps of soil moisture are critical for predicting floods, managing high tides, and scheduling crop irrigations. It is possible to map soil moisture over large areas of the Earth using orbiting satellite-based sensors. This is complicated by differences in surface roughness that affect the radar signal and interfere with the ability to accurately determine soil moisture. This review (citing 200 previous studies) summarizes the possibilities for mapping soil roughness and for minimizing the error in soil moisture mapping. Suggestions were made to use multiple radar images or different radar configurations over a single site to normalize the radar signal for roughness and improve the accuracy of soil moisture estimates. This review describes the state-of-the-science in soil moisture mapping and provides a direction forward to overcome limitations and improve map products.

Technical 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.