Radar monitoring of aeolian sand and dust transporting manifestations in desert areas

Spaceborne radar identification of desert regions as suppliers of dust into the atmosphere

“…In order to verify the proposed explanation of the mechanism of occurrence of the anomalously narrow beam scattering of radio waves suggested in paper [8], it was estimated the efficiency of radio wave scattering by a sandy surface disturbed sand ripples. To that end, in [9] was determined the maximum possible (in the case of the oblique backscatter remote sensing) back scatter factor of such a structure in the steady state (when there is no wind produced motion of the sand ripples) for the situation where the radio wave is nor mally incident upon the surface of the plane lee slope.…”

“…In the case where the near surface wind speed is less than 2 m/s, at the stage of origination of the anomalous narrow beam scattering, the saltons are characterized by a low flight speed and hence, "splashes" are accompanied by ejecting of a minimum number of reptons. Here, the mean slope of the flight trajectory of the charged sand grains that determines the slope of the ionized space boundary which bor ders the sand ripple [8] and is responsible for the "strong" radar scattering, is determined by both the saltons and reptons. This effect is clearly seen in Figs.…”

“…The experimentally proven the fact that the knocked out reptons escape in different directions in a semicircle [9] explains the rather weak dependency of the intensity of anomalously narrow beam backscat d tering on the wind direction relative to the direction (in the azimuthal plane) of radar illumination of the surface. In the case of downwind illumination, the ef fect has not been observed [8]. Aeolian transportation of sand and dust laden air upon the surface under appropriate conditions of at mospheric stratification (e. g., updrafts produced in the vortex formation) is capable of raising dust up to high altitudes [6] and spreading it over vast distances by means of strong wind currents in the upper atmosphere layers.…”

“…The problem can be solved instead with the use of space borne radar systems of remote sensing of the Earth. Paper [8] presents results of detecting the appearance of the effects of anomalous highly directional (narrow beam) backscattering of radio waves associated with the above mentioned processes. The effects are observed at practi cally the same angles of local illumination of the surface Θ = 30 o in both the radar images of deserts in Mauritania obtained by the side looking radars of the artificial satel lites of Earth: "Kosmos 1500" and "Sich 1" (the operation wavelength λ = 3.15 cm), and by the synthetic aperture ra dar (SAR) of Envisat 1 (λ = 5.6 cm) satellite.…”

Modeling of radar scattering by aeolian desert landforms

“…To date, a wide range of experimental and theoretical works has been carried out to study the nature of the formation of such structures and the transport of dustsand mixture into the atmosphere under the influence of wind (Kok et al, 2012;Kok et al, 2008;Stow, 1969;Namikas, 2003;Greeley et al, 1996;Schmidt et al, 1998;Malinovskaya, 2019). Methods for remote satellite monitoring of these phenomena have also been developed (Herrmann et al, 1999;Middleton et al, 2001;Ivanov et al, 2015a;Ivanov et al, 2015b;Ivanov et al, 2016;Ivanov, 2018;Bychkov et al, 2020a;Bychkov et al, 2020b;McHone et al, 1996;Stephen et al, 2005).…”