The Genesis and Evolution of African Easterly Waves

The genesis and evolution of easterly waves over the Atlantic Ocean are investigated with a moist multi-level quasi-geostrophic model. The origin of African waves is first re-examined as a linear instability problem of a general basic zonal flow with/without a parameterized latent heating. The method of eigenvalue-eigenfunction analysis is used. The analysis reveals that it is important to use a faithful representation of the structure of the basic flow as observed over the region of northwestern Africa. The kinetic energy of the unstable wave is primarily generated via the barotropic instability process associated with the horizontal shear near the 650 mb level. But the vertical shear of the zonal flow also strongly influences the thermal structure of the unstable wave. It has a thermally indirect secondary circulation centering at about 550 mb and a thermally direct circulation centering at about 850 mb. The effect of the self-induced latent heating strongly depends upon the particular baroclinic structure. The growth rate, the propagation speed and the overall structure of the observed easterly waves (Reed et al., 1977) are well reproduced in the model.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Atmospheric Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Kwon, Hyeok Joe

• Physics, Atmospheric Science

Identifier

(UMI)AAI8823177

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70925