The Generation of African Waves

A linearized, pseudospectral, primitive equation model is used to simulate the response of the low level easterly jet over northern Africa to perturbations on the scale of African waves. The model results show that the jet is unstable due to its horizontal and vertical shears. The most unstable wave...

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Bibliographic Details
Published in:Journal of the atmospheric sciences 1976-01, Vol.33 (10), p.1955-1969
Main Author: Rennick, Mary Alice
Format: Article
Language:English
Online Access:Get full text
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Summary:A linearized, pseudospectral, primitive equation model is used to simulate the response of the low level easterly jet over northern Africa to perturbations on the scale of African waves. The model results show that the jet is unstable due to its horizontal and vertical shears. The most unstable wave supported by the jet has a wavelength of 3000 km and a period of 2.0-2.5 days. It attains its maximum intensity at the 700-mb level, near 14 degrees N. This compares favorably with the characteristics of the observed waves. The kinetic energy of the waves grows at the expense of the kinetic energy of the mean jet. Energy is transferred at approximately equal rates by the horizontal and vertical Reynolds stresses. Energy conversions involving available potential energy are nearly an order of magnitude smaller, reflecting the fact that the kinetic energy of the wave accounts for about 90% of the total wave energy. The characteristics of the most unstable wave are virtually unchanged when a crude parameterization of latent heat release is included in the model.
ISSN:0022-4928
1520-0469
DOI:10.1175/1520-0469(1976)033<1955:TGOAW>2.0.CO;2