The Large-Scale Movement of Saharan Air Outbreaks over the Northern Equatorial Atlantic

作者：Toby Nahum Carlson, Joseph M. Prospero · 发表于：Journal of applied meteorology · 年份：1972 · DOI：10.1175/1520-0450(1972)011<0283:tlsmos>2.0.co;2 · 被引用次数：692 · 研究领域：Atmospheric aerosols and clouds、Climate variability and models、Atmospheric chemistry and aerosols

The intense and prolonged heating of air passing over the Sahara during the summer and early fall months forms a deep mixed layer which extends up to 15–20,000 ft during July, the warmest month. The dust-laden heated air emerges from West Africa as a series of large-scale anticyclonic eddies which move westward over the tropical Atlantic above the trade-wind moist layer, principally in the layer between 5000 and 15,000 ft (600–800 mb). Measurements made during BOMEX show that this Saharan air is characterized by high values of potential temperature, dust and radon-222 which confirm a desert origin. As the parcels of air within the layer proceed across the Atlantic the continuous fallout of particulate matter and the mixing at the base of the layer cause dust to be transferred to the lower levels where its concentration may become sufficiently great to produce dense haze at the surface over wide areas over the Atlantic and Caribbean in the latitude belt 10–25N. Nevertheless, measurements indicate that the dust concentration and associated haziness are greater at 10,000 ft than at the surface. The presence of Saharan air over the Caribbean can be recognized on conventional meteorological soundings as a virtually isentropic layer within which the potential temperature is about 40C; the mixing ratio within this layer generally remains fairly constant with height with typical mean values of 2–4 gm kg−1. The upper surface of the Saharan air layer, clearly visible from above as a sh...