Document Type
Article
Publication Date
2005
Publication Title
IEEE Transactions on Geoscience and Remote Sensing
Publisher
Institute of Electrical and Electronics Engineers
Volume
43
Issue
2
First page number:
238
Last page number:
247
Abstract
The Sahara Desert includes large expanses of sand dunes called ergs. These dunes are formed and constantly reshaped by prevailing winds. Previous study shows that Saharan ergs exhibit significant radar backscatter (σ°) modulation with azimuth angle (f). We use σ° measurements observed at various incidence angles and f from the NASA Scatterometer (NSCAT), the SeaWinds scatterometer, the ERS scatterometer (ESCAT), and the Tropical Rainfall Measuring Mission's Precipitation Radar to model the σ° response from sand dunes. Observations reveal a characteristic relationship between the backscatter modulation and the dune type, i.e., the number and orientation of the dune slopes. Sand dunes are modeled as a composite of tilted rough facets, which are characterized by a probability distribution of tilt with a mean value, and small ripples on the facet surface. The small ripples are modeled as cosinusoidal surface waves that contribute to the return signal at Bragg angles only. Longitudinal and transverse dunes are modeled with rough facets having Gaussian tilt distributions. The model results in a σ° response similar to NSCAT and ESCAT observations over areas of known dune types in the Sahara. The response is high at look angles equal to the mean tilts of the rough facets and is lower elsewhere. This analysis provides a unique insight into scattering by large-scale sand bedforms.
Keywords
Backscatter; Erg; ERS scatterometer (ESCAT); NASA scatterometer (NSCAT); Remote sensing; Sahara Desert; Sand dune; Sand sheet; Seawinds scatterometer (QSCAT); Tropical rainfall measuring mission precipitation radar (TRMM-PR)
Disciplines
Earth Sciences | Environmental Monitoring | Geographic Information Sciences
Language
English
Repository Citation
Stephen, H.,
Long, D. G.
(2005).
Microwave backscatter modeling of erg surfaces in the Sahara Desert.
IEEE Transactions on Geoscience and Remote Sensing, 43(2),
238-247.
Institute of Electrical and Electronics Engineers.
http://dx.doi.org/10.1109/TGRS.2004.840646
Included in
Earth Sciences Commons, Environmental Monitoring Commons, Geographic Information Sciences Commons
Comments
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