A Study of the Eastern Atlantic Intertropical Convergence Zone: Composite Structure and Initiation of Organized Convection
Russell, James Patrick
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/77339
Description
Title
A Study of the Eastern Atlantic Intertropical Convergence Zone: Composite Structure and Initiation of Organized Convection
Author(s)
Russell, James Patrick
Issue Date
1981
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Atmospheric Science
Language
eng
Abstract
Data obtained in the GATE experiment during the summer of 1974 were analyzed to obtain the composite structure of the Intertropical Convergence Zone (ITCZ) in the Eastern Atlantic. The composite was based upon the location of the surface confluence line. Separate composites were made for disturbed and suppressed cases in each of the three data collection phases.
The results show relatively little difference between disturbed and suppressed conditions as far as the overall structure is concerned. The disturbed cases show a cold core structure in the upper levels that is not present in the suppressed composites. Relatively strong meridional inflow is present at 700 mb in the disturbed composites illustrating the dominant effect the African wave has on the modulation of convection. Phase to Phase variations were most dramatic in the direction of prevailing outflow winds near 200 mb. In Phase I these winds were directed primarily toward the southern hemisphere, while by Phase III the situation was nearly reversed with the outflow directed primarily toward the northern hemisphere.
The spectacular rainband observed on 12 August 1974 was analyzed to attempt to determine the forcing mechanism for the large amount of rainfall observed behind the African wave trough during GATE. It was found that the convection in this case was associated with a surge in the southerly winds crossing the equator. This surge appears to be a response of an advective boundary layer (Mahrt, 1972) to an imposed pressure gradient provided by an intense vortex in the 900 mb layer associated with the African wave. The well defined line orientation may be due to the southward advection of hot, dry air in advance of the 900 mb vortex which suppresses convection to the north of the surface confluence line. A comparison to other cases of intense convection behind the wave trough shows many similarities in most cases.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
