A relationship between radar backscatter and aerodynamic roughness: Preliminary results

Abstract

The ability of the wind to move particles and the flux of windblown sand are both dependent on the topographic roughness of the surface, as measured by the aerodynamic roughness (zo). For most surfaces, topographic roughness controls many of the characteristics of the radar return, and the magnitude of the radar backscatter can be regarded as a measure of the surface roughness at or near the wavelength scale. Radar backscatter data may therefore be useful in obtaining a value of aerodynamic roughness which can be used to assess aeolian sediment transport via remote sensing. In this study, calibrated LHH, CHH and KuVV radar data were used to derive characteristic backscatter coefficients (σo) for three lava flow units, an alluvial fan, and a playa surface. Preliminary analyses show that values of σo and zo both increase with topographic roughness and that there is a good correlation between the two coefficients. This correlation suggests that it may be possible to assess aerodynamic roughness directly from radar data.

Surface and aerodynamic roughness in arid and semiarid areas and their relation to radar backscatter coefficient

“…For the dune field (site 8), our results (2 × 10 −5 to 3 × 10 −4 m) are in good agreement with those from the literature, in particular those obtained in Namibia (4 × 10 −5 to 4 × 10 −4 m) [ Greeley et al , 1997], China (3 to 4 × 10 −4 m) [ Xian et al , 2002], Antarctica (5 to 9 × 10 −4 ) [ Lancaster , 2004] and USA (7 × 10 −4 ) [ Lancaster and Baas , 1998] for comparable sites (respectively, interdunal area, sandy surface with tiny cobbles, flat sand with scattered rocks, bare sand sheet). The values from the literature for salty depressions range from 1.3 × 10 −4 m (Lunar Lake [ Greeley et al , 1997]) to 6.3 × 10 −4 m (Confidence Mill Playa [ Greeley et al , 1988]). Our determination of the aerodynamic roughness length over the Chott El Jerid (site 9, 6 × 10 −4 m) is of the same order of magnitude and agrees well with the higher limit of these measurements.…”

Introduction to the Planetary Dunes special issue, and the aeolian career of Ronald Greeley

“…In lieu of that, following are some key topics in planetary aeolian studies to which he made significant contributions over the years: wind tunnel and laboratory experiments (Greeley et al, 1974(Greeley et al, , 1980(Greeley et al, , 1981(Greeley et al, , 1982(Greeley et al, , 1984a(Greeley et al, ,b, 2000b(Greeley et al, , 2003aGreeley and Iversen, 1985;Lorenz et al, 2005;Neakrase et al, 2006;Neakrase and Greeley, 2010); erosion and abrasion by wind-blown sand (Greeley et al, 1982;Greeley and Iversen, 1985;Bridges et al, 1999;Golombek et al, 2006;Thomson et al, 2008); particle motion induced by the wind White et al, 1976;Greeley et al, 1976Greeley et al, , 1980Greeley et al, , 1988Greeley andIversen, 1985, 1987;Greeley, 2002;Sullivan et al, 2008); dust mobilization and dust devils (Greeley et al, 1981(Greeley et al, , 2000b(Greeley et al, , 2003a(Greeley et al, , 2004b(Greeley et al, , 2006bGreeley and Iversen, 1985;Greeley and Williams, 1994;Greeley, 2002;Neakrase et al, 2006;Stanzel et al, 2008;Neakrase and Greeley, 2010); field investigations of aeolian sites (Greeley andIversen, 1985, 1987;Lancaster et al, 1987;…”

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].…”