"Godzilla" African Dust Event of June 2020: Impacts of Air Quality in the Greater Caribbean Basin, the Gulf of Mexico and the United States
Résumé
On June 19, 2020, the Caribbean region started to feel the effects of an historic African (Saharan) dust plume that has been called "Godzilla" due to its large geographic extent and record amount of dust. This plume, with an area close to the size of the continental USA (8,080,464 km2), blanketed areas in the greater Caribbean Basin, the Gulf of Mexico and the southern United States. The occurrence and progression of this "Godzilla" event was predicted by several dust forecast models, among them, the global Goddard Earth Observing System-5 (GEOS-5) and the regional dust forecast model Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). According to data from the NASA Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP Lidar), the dust plume extended from the Earth's surface up to about 5 km altitude. As part of the NASA-funded summer 2020 intensive field phase of the Caribbean Air-quality Alert and Management Assistance System-Public Health (CALIMA-PH) project, eight ground-based stations in the Greater Caribbean Basin (French Guiana, Trinidad and Tobago, Martinique, Guadeloupe, Puerto Rico, Mérida-México and Miami-USA) collected surface aerosol data (e.g., PM10 and PM2.5 mass concentrations, light scattering and absorption coefficients, visibility, dust concentrations) and column aerosol data (i.e., aerosol optical depth - AOD) during the event. Using these data, together with satellite observations from the Moderate Resolution Imaging Spectroradiometer (MODIS), the Visible Infrared Imaging Radiometer Suite (VIIRS), and CALIOP, we describe the movement of the dust plume through the region and assess its impact. The event caused a decrease in visibility in the atmosphere's boundary layer of less than 3 miles in some locations, showed record values for the aerosol optical properties, and exhibited exceedances in both the US EPA air quality standard and the World Health Organization (WHO) air quality guidelines. For several days, the locations impacted by the "Godzilla" dust plume were exposed to air quality conditions ranging from "Unhealthy for sensitive groups" to "Hazardous", in cases reaching PM10 values ca. 500 μg/m3.