The Circum-global Transport of Massive African Dust and its Impacts on the Regional Circulation in Remote Atmosphere

Abstract

Abstract Atmospheric dust from the 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 June 7th-24th 2020, an extremely strong dust occurred with its westward spreading modulated by the North Atlantic Oscillation (NAO), and its eastward spreading regulated by European blocking, ultimately resulting in the circum-global 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 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 Rossby wave train and caused an 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 circum-globally transported African dust especially in Asia and North America. The new aspects on the unexpected consequences to moisture convection indicate broader roles that the dust may play in the global climate change.