Monitoring and Predicting the Intensity of Saharan Air Layer (SAL) Events Over the Caribbean Using Remote Sensing and a Dust Model Ensemble

The Saharan Air Layer (SAL) is an elevated volume of warm, dry, and stable air, ranging in depth from generally 900 to 5500 m above the surface, that originates over the Sahara Desert in Northern Africa and propagates westward over the Atlantic basin, most often during summer months. As it reaches the Caribbean islands, the SAL typically contains ambient dust particulate matter (PM) that greatly exceeds background PM10 and PM2.5 concentrations, well above healthy air quality standards. The Caribbean islands are also susceptible to the potential for drought and wildfire danger during SAL events since the associated environment is typically very dry and hot. The National Weather Service in San Juan, Puerto Rico (NWS-PR) monitors these conditions and issues air quality and fire alerts during the arrival of SAL over the greater Caribbean region. In their forecasts, the NWS-PR acquires environmental information from a variety of model- and satellite-derived products, much of it generated from the Naval Research Laboratory's Marine Meteorology Division in Monterey, CA.

This presentation provides a brief description of resources that fuse currently available satellite data and imagery, with model output to provide forecasters with the necessary tools for assessing and predicting SAL events, which in turn facilitates their issuance of appropriate air quality and fire warnings to populated regions within their area of responsibility. This report will focus on recent SAL events in June that have sent a continuous stream of dust across the Atlantic basin and have impacted the currently drought-stricken Caribbean region. In tandem with remotely sensed data (satellite-derived aerosol optical depth (AOD), elevated dust, LIDAR, total precipitable water (TPW)) and in-situ measurements from the NWS-PR and AERONET sites is a recently developed dust model ensemble comprised of seven quasi-operational aerosol and dust models known as the “International Cooperative for Aerosol Prediction Multi-Model Ensemble [ICAP-MME], Sessions, et al., 2014)”. ICAP-MME has been shown to provide fairly skillful depictions of SAL dust intensity as validated with AERONET measurements, as well as accurate predictions of the timing of SAL events toward targeted areas like Puerto Rico.