Distribution of aerosols, ozone and carbon monoxide over southern Africa

Seasonal tropospheric distributions of ozone, carbon monoxide and aerosols and their relationship with sources over southern Africa are compared for t wo airborne sampling campaigns during southern hemisphere spring 1992 (SAFA RI-92) and autumn 1994 (SA'ARI-94). Average trace gas and aerosol concentra tions from both campaigns are compared for equal spatial areas between 15 d egreesE, 15 degreesS and 35 degreesE, 30 degreesS. This study presents a fi rst estimate of air chemistry climatology over southern Africa for two seas ons and uses trajectory analysis to identify possible sources of atmospheri c trace species. Elevated chemical concentrations in the troposphere are at tributed to two principal sources - industrial emissions and biomass burnin g. Differences in southern African tropospheric chemistry are the result of seasonal variability in the frequency of fire emissions in the north and t he permanence of industrial emissions in the southeast. Seasonal variation in trace gas and aerosol concentrations over this region is largely influen ced by fire and regulated by dominant air flow patterns and strong stratifi cation into layers of polluted and unpolluted air. The season-independent s ignal is shown to be that of industrial emissions that prevail throughout t he year and determine a significant portion of the chemical conditions of t he troposphere over the subcontinent.