Identification of storm surge events over the German Bight from atmospheric reanalysis and climate model data

Abstract

Abstract. A new procedure for the identification of storm surge situations for the German Bight is developed and applied to reanalysis and global climate model data. This method is based on the empirical approach for estimating storm surge height using information about wind speed and wind direction. Here, we hypothesize that storm surge events are caused by 10 m winds with high wind speed and north-westerly direction in combination with a large-scale wind storm event affecting the North Sea region. The method is calibrated for ERA-40 data, using the data of the storm surge atlas for Cuxhaven. It is shown that using information of both: wind speed and direction as well as large-scale wind storm events improves the identification of storm surge events. To estimate possible future changes of potential storm surge events, we apply our approach to a small ensemble of three transient climate change simulations which are performed with the ECHAM5/MPIOM model under past and A1B greenhouse gas scenario forcing. We find an increase of the total number of storm surge relevant events by about 12% regarding the ensemble mean for the period from 2001 to 2100 with respect to the period from 1901 to 2000. Yearly numbers of storm surge relevant events show high interannual and decadal variability and only the time series for one of three runs shows a statistical significant increase of the yearly number of storm surge relevant events between 1900 and 2100. However, no changes in the maximum intensity and duration of these events is determined.