Organization of dust storms and synoptic-scale transport of dust by Kelvin waves

Abstract

Abstract. Based on the large-scale transport of dust driven by the winds parallel to the mountains in the Harmattan, Saudi Arabian, and Bodélé Depression dust storm cases, a detailed study of the generation of Kelvin waves and its possible role in organizing these dust storms and large-scale dust transport was accomplished. For this study, observational and numerical model analyses were done in an in depth manner. For this, MERRA reanalysis data sets; WRF-simulated high-resolution variables; MODIS Aqua and Terra images; EUMETSAT images; NAAPS aerosol modeling plots; and MERRA-2 dust scattering aerosol optical depth (AOD) modeling plots, surface observations, and rawinsonde soundings were analyzed for each of these three case studies. We found that there were meso-β-scale (horizontal length scale of 20–200 km) adjustment processes resulting in Kelvin waves only in the Harmattan and the Bodélé Depression cases. The Kelvin wave preceded a cold pool accompanying the air behind the large-scale cold front instrumental in the major dust storm. We find that this Kelvin wave organized the major dust storm in a narrow zone parallel to the mountains before it expanded upscale (meso-α to synoptic).

Influence of Orography Upon Summertime Low‐Level Jet Dust Emission in the Central and Western Sahara

“…Western Saharan orography stretching from the Atlas mountains in the north to the Aïr mountains in the south has been linked to atmospheric phenomena relevant to dust emission. Kelvin waves regularly propagate along the barrier of the Atlas mountains, organizing downslope winds and jet adjustment processes responsible for severe dust storms in the Harmattan channel (Pokharel & Kaplan, 2019). A relationship may also exist between the Atlas range and the remote Saharan boundary layer, with ascent over the mountains and compensating descent over the central Sahara (Flamant et al., 2007).…”

Dynamics of Muddy Rain of 15 June 2018 in Nepal

“…It has been stated that the capability of the wind to deflate the dust particles (erosivity), the soil's susceptibility to entrainment (erodibility), and the supply of erodible sediment are three major controlling factors on the dust emission process [8]. It is found that the downslope winds and the unbalanced adjustment processes in the lee of the mountain ranges are the terrain-induced wind storms that also lift the dust from the surface, and produce larger-scale dust aerosol mobilization, and transport [9][10][11][12][13].…”