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Wind and Structures Volume 13, Number 1, January 2010 , pages 37-55 DOI: https://doi.org/10.12989/was.2010.13.1.037 |
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Strong wind climatic zones in South Africa |
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A.C. Kruger, A.M. Goliger, J.V. Retief and S. Sekele
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| Abstract | ||
| In this paper South Africa is divided into strong wind climate zones, which indicate the main sources of annual maximum wind gusts. By the analysis of wind gust data of 94 weather stations, which had continuous climate time series of 10 years or longer, six sources, or strong-wind producing mechanisms, could be identified and zoned accordingly. The two primary causes of strong wind gusts are thunderstorm activity and extratropical low pressure systems, which are associated with the passage of cold fronts over the southern African subcontinent. Over the eastern and central interior of South Africa annual maximum wind gusts are usually caused by thunderstorm gust fronts during summer, while in the western and southern interior extratropical cyclones play the most dominant role. Along the coast and adjacent interior annual extreme gusts are usually caused by extratropical cyclones. Four secondary sources of strong winds are the ridging of the quasi-stationary Atlantic and Indian Ocean high pressure systems over the subcontinent, surface troughs to the west in the interior with strong ridging from the east, convergence from the interior towards isolated low pressure systems or deep coastal low pressure systems, and deep surface troughs on the West Coast. | ||
| Key Words | ||
| strong winds; wind climate; climate zones; South Africa. | ||
| Address | ||
| A.C. Kruger; Climate Service Division, South African Weather Service, Private Bag X097, Pretoria 0001, South Africa A.M. Goliger; Division of Built Environment, CSIR, P. O. Box 395, Pretoria 0001, South Africa J.V. Retief; Department of Civil Engineering, University of Stellenbosch, Private Bag X1, Matieland 7602, South Africa S. Sekele; Climate Service Division, South African Weather Service, Private Bag X097, Pretoria 0001, South Africa | ||