STABLE DISCONTINUITIES IN THE ATMOSPHERE OVER SOUTH-AFRICA

The thermodynamic structure of the atmosphere over South Africa is exa mined to determine the occurrence and persistence of stable discontinu ities that govern the horizontal and vertical transport of aerosols an d trace gases in the troposphere over the region. Absolutely stable la yers in which the lapse rate of temperature is less than the saturated adiabatic lapse rate, are shown to occur preferentially at similar to 700, similar to 500 and similar to 300 hPa levels over the whole of t he plateau region, with an. additional layer occurring at sub-plateau elevations at similar to 850 hPa between the coast and Escarpment. The development of the layers is almost constant throughout the year on n o-rain days and no appreciable seasonal variation is apparent. Likewis e, changing synoptic circulation patterns appear to exert no significa nt effect an. the development of the layers on no-rain days, which ove r most of South Africa occur with a frequency exceeding 80 per cent. T he persistence of the stable layering of the atmosphere over South Afr ica is shown to be an. important aspect of the climate of the region.