, Volume 43, Issue 4, pp 161-174

Thermodynamic properties of the mean circulation around southern Africa

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Summary

Distributions through the year of temperature, geopotential height and specific humidity, and of their standard deviations, over southern African radiosonde stations are studied through harmonic analysis. Characteristics of annual and semi-annual cycles vary across the subcontinent as a result of thermal and mechanical effects induced by the land mass. Over the interior plateau temperatures and geopotential heights through to 100 hPa respond directly to solar heating of the surface and resultant seasonal changes in surface-at-mosphere heat fluxes. Around the coast temperatures and geopotential heights are additionally influenced by seasonally-varying ocean-atmosphere heat fluxes. Cycles of atmospheric moisture are dependent on properties of the low-level circulation rather than on temperature per se. The results demarcate the two inversions frequently located over the subcontinent and indicate that the local subtropical jet stream is displaced latitudinally on a semi-annual cycle, lying furthest south in February and August.

With 12 Figures