Identification

Title

The influence of African easterly waves on convection over tropical Africa and the East Atlantic

Abstract

Using data from the Tropical Rainfall Measuring Mission (TRMM), the modulation of convection by African easterly waves (AEWs) is investigated over regions of the east Atlantic and tropical Africa. To explain the modulation of convection, the large-scale environment (lift, moisture, conditional instability, and shear) is also examined as a function of AEW phase in each region. Over semiarid portions of tropical Africa, unconditional rain rates are greatest in the northerly phase of AEWs due to the strong adiabatic forcing for ascent. Along the Guinea Coast, the western coast of Africa, and over the east Atlantic-where forcing for ascent is weaker-rainfall is shifted toward the trough where the air is moist. Significant contrasts in the characteristics of convection as a function of AEW phase-comparable in magnitude to regional contrasts-are also observed. In all regions, large and high echo-top convective systems are more sensitive to AEW phase than small and low echo-top systems. In semiarid regions, deep convection and large high echo-top convective systems account for a large fraction of the rainfall in the ridge and northerlies. Stratiform and small low echo-top convective systems dominate in the trough and southerlies. Convective system height and conditional rain rates increase with conditional instability and system sizes may increase with shear. Over the east Atlantic, stratiform fractions and convective system sizes and echo-top heights are greatest in the trough while the ridge is dominated by shallow convection. This is primarily related to the presence of moist air in the trough and dry air in the ridge.

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document

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http://n2t.net/ark:/85065/d7b56m6c

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Dataset language

eng

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geoscientificInformation

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reference date

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publication

effective date

2016-01-01T00:00:00Z

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publication

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2016-01-01T00:00:00Z

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Copyright 2016 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.

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None

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OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

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pointOfContact

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