Indicative hazard profile for strong winds in South Africa (original) (raw)

Strong winds in South Africa: Part 2 Mapping of updated statistics

Journal of the South African Institution of Civil Engineers

Although wind is the most important environmental action on buildings and structures in South Africa, the last comprehensive strong wind analysis was conducted in 1985. The current wind loading code is still based on the strong wind quantiles forthcoming from that analysis. Wind data available for strong wind analysis has increased about five-fold, due to the employment of automatic weather station (AWS) technology by the South African Weather Service. This makes an updated assessment of strong winds in South Africa imperative. Based on the estimation of strong winds as reported in the accompanying paper (see page 29 in this volume), the spatial interpolation of 50-year characteristic strong wind values to provide updated design wind speed maps is reported in this paper. In addition to taking account of short recording periods and the effects of the mixed strong wind climate, the exposure of the weather stations was considered and correction factors applied. Quantile values were adj...

Severe wind phenomena in Southern Africa and the related damage

Journal of Wind Engineering and Industrial Aerodynamics, 2007

This paper presents a review of the types and magnitude of strong and extreme wind events that develop over the southern portion of the African continent. The origin of such events is given, together with selected statistics and examples of damage. The differences in implications of these events on the built environment, in terms of the levels of engineering input and the context of formal and informal development, are discussed.

An updated description of the strong-wind climate of South Africa

2011

Wind constitutes the most critical environmental loading affecting the structural design of the built environment in South Africa. Over the years, several failures of buildings and structures due to wind actions have occurred, some of them resulting in loss of human lives, as well as significant financial losses (Goliger and Retief, 2002). These failures could be attributed to various factors e.g. improper design and/or construction, but also inadequate knowledge of the wind action; more specifically the wind characteristics at low elevations at a regional or local scale affecting the design of specific structures. The need for updating the environmental input into the process of determining wind loads for structural design was emphasised during the process of revising the South African Loading Code (Goliger 2007). The sparse distribution of climate stations, mainly located in large cities for the present wind maps (Milford 1985a & b) and the subsequent addition of several decades o...

Estimation of extreme wind speeds in the mixed strong wind climate of South Africa

14th Australasian Wind Enginering Society (AWES) Workshop, August 2010 The South African Weather Service, with the support of the Council for Scientific and Industrial Research (CSIR) and the University of Stellenbosch, is in the process of updating the extreme surface wind statistics for South Africa. A previous assessment was done by the CSIR in 1985 when only a limited number of climate stations over South Africa were available, which had sufficiently long time series of continuously recorded high-resolution wind data. Due to the complexity of the South African strong wind climate, which has also been updated, data produced by the different strong wind producing phenomena should be analyzed separately to improve extreme wind predictions. Previous studies exist, one which e.g. distinguished between four extreme wind-generating mechanisms for Australia. Annual extreme wind speeds are generated by different mechanisms, forthcoming from thunderstorm activity and the passages of extra...

Atlas of extreme wind and gust for South Africa

DTU Wind Energy, 2021

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Evaluation of Severe Weather Guidance Maps issued by the South African Weather Service

Daily subjective guidance maps of severe weather are issued by the South African Weather Service for the southern African region. In this study, the skill of the guidance for rainfall exceeding 25 and 50 mm/day for the period of October 2012 to March 2013 is determined using the Hydro-Estimator as well TRMM rainfall estimation fields as ground truth. Similar results are found with both rainfall estimation fields, however the statistics tends to give higher scores when applying the 25 mm/day threshold and using the Hydro-Estimator. It is also found that with both the Hydro-Estimator and the TRMM data, the guidance maps have the best skill and overall performance during January and February when most of the extreme rainfall events occur.

Strong wind climatic zones in South Africa

Wind and Structures An International Journal

Copyright: 2010 Techno Press. This is the pre-print version of the work. The definitive version is published in Wind and Structures Journal, Vol 31(1), pp 37-55 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 extr...

Extreme wind atlases of South Africa from global reanalysis data

2013

Extreme wind atlases of South Africa were developed using three reanalysis data and recently developed approaches. The results are compared with the maps produced using standard wind measurements over the region. It was found that different reanalyses with the same approach provide similar spatial distribution of the extreme wind with coarse resolution data giving smaller extreme winds. The CFSR surface winds at 38 km horizontal resolution provides the best spatial distribution of the extreme winds.