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Wind and Structures Volume 9, Number 3, May 2006 , pages 179-191 DOI: https://doi.org/10.12989/was.2006.9.3.179 |
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Errors in GEV analysis of wind epoch maxima from Weibull parents |
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R. I. Harris
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| Abstract | ||
| Parent wind data are often acknowledged to fit a Weibull probability distribution, implying that wind epoch maxima should fall into the domain of attraction of the Gumbel (Type I) extreme value distribution. However, observations of wind epoch maxima are not fitted well by this distribution and a Generalised Extreme Value (GEV) analysis leading to a Type III fit empirically appears to be better. Thus there is an apparent paradox. The reasons why advocates of the GEV approach seem to prefer it are briefly summarised. This paper gives a detailed analysis of the errors involved when the GEV is fitted to epoch maxima of Weibull origin. It is shown that the results in terms of the shape parameter are an artefact of these errors. The errors are unavoidable with the present sample sizes. If proper significance tests are applied, then the null hypothesis of a Type I fit, as predicted by theory, will almost always be retained. The GEV leads to an unacceptable ambiguity in defining design loads. For these reasons, it is concluded that the GEV approach does not seem to be a sensible option. | ||
| Key Words | ||
| extreme wind speeds; parent wind speeds; GEV; Weibull. | ||
| Address | ||
| RWDI-Anemos Ltd, Unit 4, Lawrence Way, Dunstable LU6 1BD, UK | ||