2002 Annual

Tuesday, 15 January 2002: 11:15 AM
Long-range Transport of African Mineral Aerosols to the Southeastern United States: Impact on the Environment of the Southeastern United States
Joseph M. Prospero, RSMAS/University of Miami, Miami, FL
Aerosol studies at a coastal site in Miami, Florida, for the past 23 years show that large quantities of African mineral dust are periodically carried into Florida every summer. Dust events typically last at least several days and can extend over 1-2 weeks. At least several dust episodes occur every summer. Maximum concentrations occur in July but relatively high concentrations are also observed in June and August. There is considerable year-to-year variability that is apparently linked to various meteorological factors including climate conditions in North Africa as manifested by drought. Satellite data show that African dust incursions are synoptic-scale events; consequently, dust measurements made in Miami reflect conditions that impact a large region of the southern and eastern United States. This conclusion is supported by air quality measurements which show that during the summer the highest concentrations of fine-particle mineral dust occur east of the Mississippi, not in arid western regions as one might expect. The incursion of dust events over this large region could have important implications regarding regional air quality. About a third to a half of the African dust mass falls in the size range below 2.5 Ám diameter and is thus classified by the Environmental Protection Agency as "inhalable". This raises questions about the possible impact of African dust on the human respiratory system and health. Also the very high dust concentrations can affect the radiation balance in the region and cloud nucleating processes. The fact that dust concentrations over the Atlantic and the eastern United States are linked to climate in North Africa suggests that environmental impacts over this region could change markedly in response to larger scale climate change over the coming decades.

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