The thermodynamic structure of the atmosphere over South Africa: Implications for water vapour transport

Frequent, persistent and the spatially-continuous occurrence of absolutely stable layers of air are confined to the features of the Southern African a tmospheric environment. The elevated layers occur preferentially at similar to 850 hPa (over the coastal regions only), similar to 700 hPa, similar to 500 hPa and similar to 300 hPa throughout the troposphere. They are highly effective in acting as upper air boundaries that control the free diffusio n of aerosols and trace gases (including water vapour) in the vertical and may have repercussions on scales ranging from local to synoptic. The season al stability characteristics and temporal and spatial continuity of the ele vated absolutely stable layers are examined over the eastern half of South Africa and related to a previous case study of moisture transport patterns on rain and no-rain days.