Multi-scale analysis of the meteorological processes forcing African dust ablation and transport in the extreme mid-march 2022 case

We examine the complex meteorological processes involved in the development of multiple dust storms in the middle of March 2022 over North Africa by means of multi-level high-resolution reanalysis datasets, and satellite and surface observations. These dust storms ultimately transported a remarkable amount of dust into Europe, and in particular to the Iberian Peninsula.

The analyses show that baroclinic Rossby Wave Breaking (RWB) events over two regions: the eastern North Atlantic and the western Eurasian border, resulted in the creation of a downscale confluence of low-level jets that ablated dust in the Sahara Desert. One of these active baroclinic regions involved multiple wave-breaks over western Russia and the Middle East that transported unseasonably cold air southwestward into Egypt and Sudan. A second active baroclinic region occurred along the North African Atlantic Coast where rapid downstream dispersion of energy was focused in response to very intense cyclogenesis over Labrador. The cold pool which propagated into northwestern Africa and cold air over northeastern Africa effectively sandwiched hot Saharan air in between the Hoggar and Atlas Mountain Ranges. The fronts separating these air masses became juxtaposed with the two mountain ranges creating ideal conditions for blocking and multiple barrier jets’ genesis. These barrier jets each combined with larger scale semi-geostrophic low-level jet formation, resulted in the ablation of dust into two separate large plumes both of which were transported poleward out of North Africa into Europe around a upper-level cutoff-low near Iberia slowly displacing downstream.

The blocked RWB forcing the penetration of cold air over eastern Africa constitutes a substantial difference with respect to other more frequent events where RW trains intensify, penetrate equatorward into North Africa and propagate eastward.

Work funded by MCIN/AEI/ 10.13039/501100011033 under Grant PID2020-115153RB-I00 (rROSSETA Project).