Extreme wind storms over Europe: Statistical Analyses of ERA-40

Accurate assessment of the magnitude and frequency of extreme wind speed is of fundamental importance for many safety, engineering and financial applications. We utilise the spatial and temporal consistency of the European Center for Medium Range Forecasts ERA-40 reanalysis data to determine the frequency of extreme winds over the eastern North Atlantic and Europe. The analysis of extreme winds follows two different view points: In a spatially distributed view, wind storm statistics are determined individually at each grid point over the domain, resulting in recurrence estimates of storms for each reanalysis grid point. In an integral, more generalized view, the storm statistics are determined from extreme wind indices that summarize storm magnitude and spatial extent. We investigated the quality of ERA-40 wind gust data, a parameterised forecast field, and found the wind gust values over areas of complex orography to be unrealistic. This led to the need to mask these areas from further analysis. We also used the 850hPa geostrophic wind speed which was found not to suffer from the same problems as wind gust.