Impacts of Congo Convection on Tropical Africa's circulation, rainfall and resources
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Date
2002
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Abstract
The impact of central African convection on surrounding circulation is examined. The
convection over the Congo basin is estimated using satellite OLR (Outgoing Long Wave Radiation) as an index. It is then related to the regional and global circulation. OLR indices for the Congo area 15°-30°E, 10°S-5°N are evaluated for JAS and MAM seasons and associated circulation regimes are considered. Seasonal OLR over the Congo for the period 1974-2000 is correlated with selected parameters in the horizontal and vertical plane, in the domain 60°W-90°E, 20°S-15°N. The correlation between rainfall and crop related GDP (Gross Domestic Product) for selected countries which are influenced by Congo convection was evaluated. For cases examined it was found that 20-48% of variance in the GDP growth rate was attributable to local rainfall, clearly showing that human dependence on agricultural activities makes Africa particularly sensitive to shifts in monsoon convection.
Convection over central Africa plays a key role in influencing the weather over the region through latent heating. The influence of Congo convection is short lived compared to that of nearby Indian and Atlantic Ocean monsoons, because of the relative small size and terrestrial nature of the Congo basin. Yet the influence is significant as indicated by the following.
• Zonal winds accelerated from the west from 60 W (Atlantic) through 40 E $ahel).
The relationship extends from surface to 500hPa with a peak at 600hPa.
• Upper westerly winds are weakened over South Africa during JAS season, with the
Congo convection leading.
• Congo convection tends to lead the zonal stratospheric QBO, which suggests that the
convection is one of the sources of energy for quasi-biennial oscillations in the global
climate system,
• Monsoon winds converge over eastern and western coasts of tropical Africa.
• During a wet scenario in JAS season, the Atlantic Walker cell has an ascending arm
over the Congo basin, transporting latent heat to the upper atmosphere and higher
latitudes, generating standing rossby waves.
Description
Thesis submitted to the Faculty of Science
For the degree of Master of Science
Department of Geography and Environmental Studies
University of Zululand, 2002
Keywords
Convection (Meteorology): Congo, Convection (Meteorology): Africa., Rain and rainfall; Africa.