Applications of spaceborne radar laboratory data to the study of aeolian processes

Abstract

Abstract. Aerodynamic roughness (z0) is an important parameter in studies of sand and dust transport, as well as atmospheric circulation models. Aerodynamic roughness is a function of the size and spacing of surface roughness elements and is typically determined at point locations in the field from wind velocity profiles. Because field measurements require complex logistics, z0 values have been obtained for very few localities. If radar can be used to map z0, estimates can be obtained for large areas. In addition, because aerodynamic roughness can change in response to surface processes (e.g., flooding of alluvial surfaces), radar remote sensing could obtain new measurements on short timescales. Both z0 and the radar backscatter coetficient cr ø are dependent on topographic roughness at the submeter scale, and correlation between these two parameters was developed based on radar data obtained from aircraft (AIRSAR). The Spaceborne Radar Laboratory (SRL) afforded the opportunity to test the correlation for data obtained from orbit. SRL data for sites in Death Valley, California; Lunar Lake, Nevada; and Gobabeb, Namibia, were correlated with wind data and compared with previous radar z0 relations. Correlations between cr ø and z0 for L band (X: 24 cm) HV (H, vertically and V,vertically polarized modes) L band HH, and C band (X -5.6 cm) HV compare favorably with previous studies. Based on these results, maps of z0 values were derived from SRL data for each site, demonstrating the potential to map z0 for large vegetation-free areas from orbit using radar systems. IntroductionAeolian processes are prominent in arid and coastal regions but can occur wherever loose particles are available for movemcnt by the wind. In addition to hazards created by sand and dust storms, the migration of sand over roads, agricultural fields, and other cultural features has negative economic impacts. Moreover, because aeolian processes involve the interaction of the atmosphere and Earth's surface. they can influence the climate. Aeolian processes can occur frequently and on short timescales, resulting in rapid surface changes. Remote sensing affords the opportunity to monitor these changes and, in some cases, allows the prediction of potential aeolian activity. Remote sensing in the visible spectrum has been used to map sand dune fields [e.g., Breed et al.

Aerodynamic roughness height for gravel-mantled megaripples, with implications for wind profiles near TARs on Mars

“…Bold entries are 3-anemometer measurements obtained on the specified date. Literature data are mostly derived from Tables 6 and 7 of Marticorena et al (2006) and Table VIII Greeley et al (1997).…”

Vegetation in Drylands: Effects on Wind Flow and Aeolian Sediment Transport

“…Greeley et al [159,160] established relations between z 0 obtained from wind velocity profile data and radar backscatter cross sections. Marticorena et al [161] evaluated the application of a bidirectional reflectance model to estimate roughness properties, while Marticorena et al [162] found a relation between radar backscatter coefficients in the C band and z 0 that suggested potential for remote sensing the roughness length at broad scales.…”

Evaluating the Relationship between Field Aerodynamic Roughness and the MODIS BRDF, NDVI, and Wind Speed over Grassland

“…Most of the current research on remote sensing-based AR estimations is focused on farmland, forest, and desert regions. Researchers have used the normalized difference vegetation index (NDVI), the airborne Light Detection and Ranging (LIDAR), multi-angle observations, radar backscattering coefficients, and a morphology method to estimate the AR over these land surfaces [3][4][5][6][7][8][9][10][11][12].…”