The Role of Easterly Waves on African Desert Dust Transport

Abstract

Mineral aerosols from North Africa represent one of the largest sources of aerosols available to the atmosphere, and their generation and transport are thought to be modulated by African easterly waves. In this study, the relationships between easterly wave activity and model simulations of desert dust entrainment and transport are investigated. National Centers for Environmental Prediction–National Center for Atmospheric Research reanalysis datasets are used to both evaluate easterly wave activity and drive a transport model simulation of desert dust. The focus of this study is on boreal summer, when easterly wave activity maximizes. Periods of high easterly wave activity are identified using filtered (2.5–10 days) relative vorticity at 700 hPa over the tropical Atlantic Ocean. Lag composites of relative vorticity and simulated surface dust concentrations are used to investigate the influence of easterly waves on the spatial transport patterns. A comparison between lag composites of available in situ desert dust data at Barbados and model simulation suggests that the model results are consistent with the variability at Barbados. The results show that approximately 20% of the dust entrainment into the atmosphere over a broad region of North Africa is associated with easterly wave activity, suggesting that easterly waves may regulate desert dust entrainment into the atmosphere. About 10%–20% of the seasonal variability of desert dust concentrations across the North Atlantic is related to easterly waves, which suggests that easterly waves modulate the transport of desert dust.