The Circumglobal Transport of Massive African Dust and Its Impacts on the Regional Circulation in Remote Atmosphere

Abstract

Abstract Atmospheric dust from North Africa, the largest and most persistently active dust source over the world, spreads widely in the Northern Hemisphere and plays essential roles in the Earth environment evolution. During 7–24 June 2020, an extremely strong dust event occurred with its westward spreading modulated by the North Atlantic Oscillation (NAO) and its eastward spreading regulated by European blocking, ultimately resulting in the circumglobal transport of African dust. The Mediterranean low pressure linked to the European blocking dipole was the key to facilitating the eastward transport of dust. This record-breaking African dust episode caused a notable diurnal precipitation decrease of 0.98 mm day −1 over northeastern India and a decrease of 1.55 mm day −1 over central North America, which was ascribed to the effect of dust-induced radiative heating on large-scale circulation. It triggered a Rossby wave train and caused anomalous high pressure over northeastern India, which weakened the India summer monsoon and consequently inhibited the occurrence of precipitation. Dust-induced radiative heating also supported the stability in the anomalous warm high over North America, further repressing import of moisture from Atlantic. Ambient moisture and atmospheric instability also presented consistent variation over North America and India characterized as strengthen descending motion and sharply reduced moist convection. This study reports, for the first time, the strong modulation of regional circulation by circumglobally transported African dust, especially in Asia and North America. The new aspects on the unexpected consequences on moisture convection indicate broader roles that the dust may play in the global climate change. Significance Statement This study elucidated the circumglobal transport of African dust and revealed its modulation to large-scale circulation with the consequent impact on regional precipitation in remote downstream regions. The circumglobal transport of African dust was represented in two pathways, with its westward spreading modulated by the North Atlantic Oscillation and its eastward spreading regulated by European blocking. The dust-induced radiative heating triggered a Rossby wave train and caused anomalous anticyclones dominating central North America and northeastern India, ultimately resulting in a notable diurnal precipitation decrease of 0.98 and 1.55 mm day −1 over northeastern India and central North America, respectively. These results highlight broader roles that African dust may play in the global climate change in the future.

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