The Atmospheric Drivers of the Major Saharan Dust Storm in June 2020. Issue 24 (27th December 2020)

• Record Type: Journal Article
• Authors: Francis, Diana; Fonseca, Ricardo; Nelli, Narendra; Cuesta, Juan; Weston, Michael; Evan, Amato; Temimi, Marouane
• Is Part Of: Geophysical research letters. Volume 47:Issue 24(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-12-27
• Subjects: African Easterly Jet -- intertropical discontinuity -- monsoon trough -- Saharan dust storms -- Saharan heat low -- subtropical high; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL090102
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: This study investigates the atmospheric dynamics of the major dust storm that occurred in June 2020 over the Sahara and during which dust clouds associated with the highest‐on‐record aerosol optical depths were transported toward the America. An anomalous atmospheric circulation pattern in the mid‐latitudes, linked to a circumglobal wavetrain, resulted in the development of a subtropical high‐pressure system to the west of the Saharan heat low. This created a pressure dipole and generated anomalously strong northeasterlies over the Sahara, which caused continuous dust emissions over 4 days. Occurring along the northern fringes of the intertropical discontinuity, the dust was transported to higher altitudes (6 km) by the strong updraft in this region. This injected the dust at the African Easterly Jet (AEJ) altitudes and favored a rapid westward long‐range transport. The AEJ was also anomalously strong, being strengthened by the anticyclonic circulation associated with the anomalous high. Plain Language Summary: Dust is an important constituent of the Earth's atmosphere, with a wide range of impacts ranging from human health to effects on climate. In June 2020, massive amounts of dust were lifted from the Sahara, the major dust source region in the world, and transported all the way into the Americas across the tropical Atlantic Ocean. This event was caused by the development of a subtropical high‐pressure system over northwest Africa which resulted in sustained strong northeasterlies over the Sahara generating continuous dust emissions for 4 days. Due to the strong low‐level convergence along the intertropical discontinuity region, the dust was lifted to roughly 5–6 km above the surface, and then transported westward by the stronger mid‐atmospheric winds (>20 m s −1 ). At Cape Verde and over large swaths of the Atlantic Ocean, the amount of dust suspended in the atmosphere was associated with the largest aerosol optical depths on record. Key Points: The dust storm was triggered by the development of a subtropical high off the coast of West Africa embedded in a circumglobal wavetrain The stationary subtropical high increased the north‐south pressure gradient over the Sahara and generated sustained strong northeasterlies The anticyclonic circulation associated with the high intensified the African Easterly Jet favoring a rapid westward transport of the dust plumes