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Characteristics of African Easterly Waves

  • Chapter
A Half Century of Progress in Meteorology: A Tribute to Richard Reed

Part of the book series: Meteorological Monographs ((METEOR))

Abstract

African easterly waves [AEWs, the term now preferred by R. Reed (2001, personal communication)] are synoptic-scale disturbances that form over tropical northern Africa and propagate westward, in a nearly unbroken progression, across Africa and the Atlantic Ocean during the summer months. Piersig (1936) was the first to describe a type of cyclones on historical surf ace weather charts that included the eastern tropical Atlantic and must have been the surface part of an unobserved AEW. He reported that these cyclones moved westward in the trade wind belt and occurred most frequently in August and September near the West African coast between 5° and 20°N. In view of the upstream location of these cyclones from the North Atlantic breeding grounds of hurricanes and their seasonal similarity to hurricanes, he speculated that the disturbances could be the precursors of some hurricanes. Subsequently, Hubert (1939) tracked a disturbance from near 5°W over Africa westward to the West African coast. He pointed out that if he extrapolated the disturbar..ce westward to the central Atlantic, at a similar speed, it would have arrived in the general area, at about the same time, where the 1938 New England hurricane wa; first detected.

“The energetics of the [easterly] waves in the Atlantic ITCZ are seen to be quite different from those of the waves in the Pacific ITCZ. In the Atlantic ITCZ the strongest upward motions occur at relatively low levels in the trough where the temperature anomaly is negative. Thus upward motion is correlated with low temperatures and eddy kinetic energy is converted to eddy available potential energy. In the Pacific ITCZ on the other hand, the largest rising motions occur in the upper part of the trough where the temperature anomaly is positive, and the energy conversion is in the opposite direction.” — (Reed 1978)

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  1. Cooperative Institute of Marine and Atmospheric Studies, Miami, Florida, USA

    Robert W. Burpee

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Richard H. Johnson Robert A. Houze Jr.

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© 2003 American Meteorological Society

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Burpee, R.W. (2003). Characteristics of African Easterly Waves. In: Johnson, R.H., Houze, R.A. (eds) A Half Century of Progress in Meteorology: A Tribute to Richard Reed. Meteorological Monographs. American Meteorological Society, Boston, MA. https://doi.org/10.1007/978-1-878220-69-1_7

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  • DOI: https://doi.org/10.1007/978-1-878220-69-1_7

  • Publisher Name: American Meteorological Society, Boston, MA

  • Online ISBN: 978-1-878220-69-1

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