Coupled Model Inter-comparison Project Phase-5 Weather Research and Forecasting (CMIP5-WRF) Simulations Quantifying Anthropogenic Forcing and Saharan Long-range Dust Transport

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).

Satellite images sometimes show a great brown plume of airborne dust covering the Atlantic ocean from West Africa to the Caribbean. The dust plume, lofted from the Sahara desert and blown downwind for thousands of miles, is extensive and thick enough to affect world climate through its radiative effects, and enough dust crosses the Atlantic to affect air quality in the Carribean and the southeast US. More locally, the dust is a public health challenge throughout North and West Africa, linked to asthma, bronchitis, acute respiratory infections, and other conditions. The substantial impacts of Saharan dust motivate research on the likely changes in dust emission and transport due to global climate change.

This project considers likely changes in Saharan dust emission and transport over the 21st century using computer simulations from a regional model, the Weather Research and Forecasting (WRF) model with the dust module from the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model. WRF is integrated over West Africa and the downwind Atlantic using boundary conditions from global reanalysis products and global model simulations of future climate change. Global model simulations are taken from the archive of the Coupled Model Intercomparison Project version 5 (CMIP5) and use three different estimates of likely future emissions of greenhouse gases.

The work focuses on changes in atmospheric circulation and their likely effects on the lofting and transport of Saharan dust. Motivation for the work comes from the association between Saharan dust and the North Atlantic Oscillation (NAO), a large-scale oscillation in sea level pressure between the Icelandic Low and the Azores High that causes changes in the strength of the surface winds over the Atlantic north of the equator. A further consideration is the extent to which intensification of the Saharan Heat Low in a warming climate could cause strengthening of surface winds which could in turn stir up more dust from the desert. Warming-induced changes in the intertropical convergence zone (ITCZ) are also examined as a potential influence on Saharan dust transport across the Sahel and into the Guinea region.

The health impacts of Saharan dust make the project societally relevant as well as scientifically interesting. One consideration here is that West Africa is currently home to roughly 350 million people and the population is expected to more than double by 2050. Another is that changes in the dust content of air over the Atlantic has implications for both US air quality and the formation of landfalling hurricanes. In addition, the project would provide support and training to a postdoctoral fellow and a graduate student, as well as an undergraduate student working on an hourly basis. Project participants participate in the campus EnvironMentors program, developing a project for a high school student to work on during the academic school year.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.