Distribution of aerosols, ozone and carbon monoxide over southern Africa

Distribution of aerosols, ozone and carbon monoxide over southern Africa

Grant A. Kirkman, Stuart J. Piketh, Meinrat O. Andreae, Harold J. Annegarn and Günter Helas
(South African J. Sci. 96, 2000, 423-431)

Seasonal tropospheric distributions of ozone, carbon monoxide, and aerosols and their relationship to sources over southern Africa are compared for two airborne sampling campaigns during southern hemisphere (SH) spring (SAFARI-92) and autumn 1994 (SA’ARI-94). Average trace gases and aerosol concentrations from both campaigns are compared between seasons for equal spatial areas (blocks) between 15° E, 15° S and 35° E, 30° S. This study proposes an air chemistry climatology over southern Africa for the two seasons and uses trajectory analysis to identify possible sources of atmospheric trace species.

Elevated tropospheric chemical concentrations are attributed to two source categories – industrial and biomass burning emissions. Differences in regional tropospheric chemical characteristics are the result of seasonal variability in the frequency of fire emissions in the north and the permanence of industrial emissions in the southeast of the study region. Seasonal variation in trace gas and aerosol concentrations over southern Africa is largely influenced by fire and is regulated by the dominant air flow patterns and a strong stratification into layers of polluted and unpolluted air. The season-independent signal is shown to be that of industrial emissions that prevail throughout the year and determine a significant portion of the regional chemical conditions.

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