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|Title:||A Study of the Eastern Atlantic Intertropical Convergence Zone: Composite Structure and Initiation of Organized Convection|
|Author(s):||Russell, James Patrick|
|Department / Program:||Physics|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Physics, Atmospheric Science|
|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.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.
|Date Available in IDEALS:||2015-05-13|