Preprints
https://doi.org/10.5194/egusphere-2023-2896
https://doi.org/10.5194/egusphere-2023-2896
08 Jan 2024
 | 08 Jan 2024

The Emission, Transport, and Impacts of the Extreme Saharan Dust Storm in 2015

Brian Harr, Bing Pu, and Qinjian Jin

Abstract. Each summer, the Saharan Air Layer transports massive amounts of mineral dust across the Atlantic Ocean, affecting weather, climate, and public health over large areas. Despite the considerable impacts of African dust, the causes and impacts of extreme trans-Atlantic African dust events are not fully understood. The “Godzilla” trans-Atlantic dust event in 2020 has been extensively studied, but little is known about other similar events. Here we examine the June 2015 event, the second strongest trans-Atlantic African dust event during summers over 2003–2022. This event was characterized by moderately high dust emissions over western North Africa and an extremely high aerosol optical depth (AOD) over the tropical North Atlantic. The high dust loading over the Atlantic is associated with atmospheric circulation extremes like the “Godzilla” event. Both the African easterly jet (AEJ) and Caribbean low-level jet (CLLJ) are greatly intensified, along with a westward extension of the North Atlantic subtropical high (NASH), all of which favor the westward transport of African dust. The enhanced dust emissions are related to anomalously strong surface winds in dust source regions and reduced vegetation density and soil moisture over the northern Sahel.

The dust plume reduced surface net shortwave radiation over the eastern tropical North Atlantic by about 25 W m-2 but increased net longwave flux by about 3 W m-2. In contrast to the “Godzilla” event, the 2015 event had minor air quality impacts on the U.S., partially due to the extremely intensified CLLJ that dispersed the dust plume to the Pacific.

Brian Harr, Bing Pu, and Qinjian Jin

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Brian Harr, Bing Pu, and Qinjian Jin
Brian Harr, Bing Pu, and Qinjian Jin

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Short summary
We found that the formation of the extreme trans-Atlantic African dust event in June 2015 is associated with a brief surge in dust emissions over western North Africa and extreme circulation patterns, such as the greatly intensified easterly jets, that facilitated the westward transport of dust. The dust plume modified radiative flux along its transport pathway but had minor air quality impacts on the U.S. as the record-high Caribbean low-level jet advected part of the plume to the Pacific.