WRF-CHEM Simulation of the 2020 Godzilla Dust Plume in North Africa.

Forecasting dust storms days to weeks before they occur is essential to monitoring air quality for sensitive groups (persons with pre-existing respiratory problems). In June 2020, a massive dust plume erupted from North Africa and transported to the Caribbean Basin and North America across the North Atlantic Ocean in a matter of days to a week. In this study, we investigate the Godzilla dust event using the Weather Research and Forecasting Model (WRF) coupled with Chemistry (WRF-CHEM). An analysis of aerosol optical depth (AOD) for June 2020 from AERONET and MODIS, and the WRF-CHEM simulations showed increased dust emissions on June 14 over the West African dust sources (e.g., Mauritania, Mali, and Algeria), but the maximum transport of dust out of the African continent is observed on June 18. The simulations showed the Godzilla plume elevated from the surface to an average altitude of about 6 km over the African coast, and decreased in magnitude by the time the plume reached 32W. We found that a total of 38, 34, and 32 Tg of dust crossed the North Atlantic at 26.52W, 29.53W, and 32.17W respectively during the event (June 1–30), showing an average deposition rate of about 1 Tg per a degree change in longitude. The WRF-Chem simulations reveal an enhanced North Atlantic Subtropical High Pressure (NASH), and a well-developed Saharan Heat Low (SHL) created a circulation pattern with a meridional component which trapped the dust over West Africa for about 3 days. The presence of an upper-level high pressure system over the Sahara suppressed the African Easterly Jet (AEJ) on June 14–16 which also contributed to the accumulation of dust over West Africa. This high-pressure system decayed by June 18, allowing the AEJ to establish, thus leading to westward advection of dust.