The atmosphere, aerosols, trace gases and biogeochemical change in southern Africa : a regional integration : START Regional Syntheses

Abstract

Attention is focused on temperature and rainfall changes occurring over the subcontinent of southern Africa, on atmospheric circulation and transport of aerosols and trace gases in the vertical and horizontal, and on repeated recirculation of atmospheric constituents over the region. It is shown that most air, and whatever is contained therein, exits the subcontinental airspace in a major plume moving to the east over the Indian Ocean at 31^oS towards Australia and New Zealand. On occasions, the plume may be discernible over Australasia. Some of the consequences of sulphur emission and transport of sulphate aerosols over the region are considered and it is shown that on occasions sulphates from South Africa may be observed in Kenya and beyond. The possible role of aerosols in diminishing and enhancing regional rainfall is examined. The contribution of atmospheric particulates in the biogeochemical cycling of nutrients in terrestrial and marine ecosystems is illustrated by showing that airborne nitrates and phosphates contribute significantly to the balancing of the papyrus nutrient budget in the Botswana wetland ecosystem of the Okavango Delta region. Future climate scenarios also are considered. It is concluded that changing regional climate is one of the major driving forces leading to biogeochemical changes in terrestrial and marine ecosystems sustaining the region.