Keywords
Backscatter, ERS Scatterometer (ESCAT), NASA Scatterometer (NSCAT), sand dune, sand sheet, SeaWinds Scatterometer (QSCAT)
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 (∅). We use σ˚ measurements observed at various incidence angles and ∅ 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.
Original Publication Citation
Stephen, H., and D. G. Long. "Microwave Backscatter Modeling of Erg Surfaces in the Sahara Desert." Geoscience and Remote Sensing, IEEE Transactions on 43.2 (25): 238-47
BYU ScholarsArchive Citation
Long, David G. and Stephen, Haroon, "Microwave backscatter modeling of erg surfaces in the Sahara desert" (2005). Faculty Publications. 396.
https://scholarsarchive.byu.edu/facpub/396
Document Type
Peer-Reviewed Article
Publication Date
2005-02-01
Permanent URL
http://hdl.lib.byu.edu/1877/1074
Publisher
IEEE
Language
English
College
Ira A. Fulton College of Engineering and Technology
Department
Electrical and Computer Engineering
Copyright Status
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