Insurance loss model vs meteorological loss index – How comparable are their loss estimates for European windstorms?

Abstract. Windstorms affecting Europe are among the natural hazards with the largest socio-economic impacts. Therefore, many sectors like society, economy or the insurance industry are highly interested in reliable information on associated impacts and losses. There are different metrics to quantify windstorm-related losses, ranging from simple natural hazard databases over loss indices based on meteorological variables to more complex insurance loss (catastrophe) models. In this study, we compare estimated windstorm losses using the meteorological Loss Index (LI) with losses obtained from the European Windstorm Model of Aon Impact Forecasting. To test the sensitivity of LI to different meteorological input data, we furthermore contrast LI based on the reanalysis dataset ERA5 and its predecessor ERA-Interim. We focus on similarities and differences between the datasets in terms of loss values and storm rank for specific storm events in the common reanalysis period across 11 European countries. Our results reveal higher LI values for ERA5 than for ERA-Interim for all of Europe, coming mostly from a higher spatial resolution in ERA5. The storm ranking is comparable for Western and Central European countries for both reanalyses. Compared to Aon’s Impact Forecasting model, LI ERA5 shows comparable storm ranks. However, LI seems to have difficulties in distinguishing between extreme windstorms with high losses and those with only moderate losses. The loss distribution in LI is thus not steep enough and the tail is probably on the short side, yet it is an effective index, precisely because of its simplicity, suitable for estimating the impacts and ranking storm events.