Enhancement of the United States extreme wind database and implications for extreme wind climatology
Despite the substantial progress made in recent years to improve the characterization of extreme wind climatology in the contiguous United States, uncertainties still remain in its formal quantification. The importance of an accurate assessment of extreme wind climate is paramount, however, due to the outsized weight that the “basic wind speed” value carries in computations of design wind loads specified in ASCE 7 standards. One of many avenues towards improving the accuracy of basic wind speed values is improving the recorded wind observations from which basic wind speeds are derived. The aim of this study is enhance this body of observations—called the extreme wind database—and to provide additional techniques of improving the understanding of extreme wind climatology in the United States. The existing extreme wind database, formed using the Integrated Surface Dataset (ISD) 3505, was improved most significantly by nearly doubling its spatial resolution by extending the length of time over which observations are reported by approximately 10 years. Two additional techniques were developed that aimed to address temporal and spatial resolution issues related to climatology characterization. One of these employed the use of high temporal resolution wind observations from the Dataset 6405 (DS 6405) and the other made use of high spatial resolution wind observations obtained from the Oklahoma Mesonet (OKM). The improvements and additional techniques were quantified using a standardized extreme value analysis procedure to produce a common metric for comparison: a primordial basic wind speed analog called “V50” that can be compared across datasets of highly disparate character. Full suites of V50 values were generated for a control group of wind observation databases (i.e. existing databases) as well as a set of databases containing the improvements and additional techniques employed. Using numerous graphical and geospatial analysis methods, the results of database improvements were compared to the control groups in the context of United States extreme wind climatology. It was found that, with regard to improvements of the existing extreme wind database, a doubling of the network spatial density and the extension of time histories led to a slight increase in basic wind speed estimates in most areas of the United States. Regional characteristics of basic wind speed contours were able to be more clearly identified as well. The technique for implementing high temporal resolution data from DS 6405 was found to unviable owing to the widespread existence of unrealistic wind records within the parent dataset that could not be adequately controlled. The spatial resolution improvement technique employing Oklahoma Mesonet observations, however, yielded more promising results. Using a comparison analysis of discrete, co-located wind events, it was found that the less spatially-dense network used to create the existing extreme wind database may not adequately capture small-scale extreme wind events as capably as the more spatially-dense Oklahoma Mesonet. This implies that the existing database, as well as the overarching methodology used to create it, may be systematically insufficient in regards to extreme wind observations. While it is assumed that this insufficiency has significant impacts on United States extreme wind climatology evaluations, further work is needed to quantify these impacts in a more generalized context.
wind, extreme, climatology, database, ASOS, United States, ISD 3505, DS 6405, Oklahoma Mesonet, extreme value analysis, observation network
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign