The overall feature of the distribution of the mean annual precipitation or MAP in South Africa is that it decreases fairly uniformly westwards from the escarpment across the interior plateau. Between the escarpment and the ocean in both the southern and the eastern coastal margins there is an increase of complexity of rainfall patterns as a result of the irregularities of terrain. The Drakensberg Mountains run almost parallel to the coast for the entire eastern side of the country, causing the irregular rainfall patterns in that part of South Africa.

About 35% of Southern Africa receives less than 300 mm per annum as a result of the presence of subtropical high pressure cells which inhibit rainfall generation because of the predominantly subsiding air.

 

Air pollution The motor car is an important contributor to air pollution in South Africa. The transport sector (including aeroplanes, ships, trains and road vehicles) contributes 44% of the total national nitric oxide emissions and 45% of the total national volatile organic carbon emissions (VOC). Road vehicles, rather than trains, aircrafts and ships, contribute the most to the total carbon dioxide, nitric oxide and VOC emissions from the transport sector (94%, 53% and 89% respectively). Road vehicles also contribute to lead emissions, especially in the urban areas.