Spatial and temporal distribution of tropospheric ozone over Southern Africa

[摘要] Tropospheric ozone over southern Africa is characterised using the Southern AfricaRegional Science Initiative (SAFARI) 2000 aircraft datasets collected from surface tojust above the boundary layer, and satellite remotely sensed ozone column depth.Ozonesonde datasets for Irene, South Africa; Lusaka, Zambia; Nairobi and Malindi,both Kenyan stations were, used to supplement the aircraft and satellite data. The periodstudied is the dry biomass burning season between August and September, 2000Source areas of ozone precursors have been identified by trajectory analysis. Fivepoint,back trajectory clusters in the region reveal well-defined air mass transportcorridors. Enhanced ozone concentrations, above 70 ppb, were regularly encountered inthe lower troposphere (3.5 km above ground level) in air masses distributed over thesub-region by distinct re-circulation pathways, which prevailed during the study period.Occasional, episodes of significant higher ozone pollution, above 100 ppbv areidentified.Savannah fire products transported from seasonal biomass burning regions ofwestern Zambia, northern Zimbabwe and Mozambique have been found to be the majorsources of ozone pollution over the sub-region. Another source, though on a lesserscale, is the Highveld industrial region of South Africa.In situ air observations established that the western and eastern sectors of thesouthern Africa, north of 23°S latitude, were the major sources of regional ozoneprecursor gases. The regions southwards of 23°S were observed to have lower ozonepollution.

[发布机构] University of the Witwatersrand