German Bight storm activity, 1897–2018

Abstract

This study investigates the evolution of German Bight (southeastern North Sea) storminess from 1897 to 2018 through analysing upper quantiles of geostrophic wind speeds, which act as a proxy for past storm activity. Here, geostrophic wind speeds are calculated from triplets of mean sea level pressure observations that form triangles over the German Bight. The data used in the manuscript are provided by the International Surface Pressure Databank and the national meteorological services of Denmark, Germany, and the Netherlands. The derivation of storm activity is achieved by enhancing the established triangle proxy method via combining and merging storminess time series from numerous partially overlapping triangles in an ensemble-like manner. The utilized approach allows for the construction of robust, long-term and subdaily German Bight storminess time series. Further, the method provides insights into the underlying uncertainty of the time series. The results show that storm activity over the German Bight is subject to multidecadal variability. The latest decades are characterized by an increase in activity from the 1960s to the 1990s, followed by a decline lasting into the 2000s and below-average activity up until present. The results are backed through a comparison with reanalysis products from four datasets, which provide high-resolution wind and pressure data starting in 1979 and offshore wind speed measurements taken from the FINO-WIND project. This study also finds that German Bight storminess positively correlates with storminess in the NE Atlantic in general. In certain years, however, notably different levels of storm activity in the two regions can be found, which likely result from shifted large-scale circulation patterns.

Improving seasonal predictions of German Bight storm activity

“…The calculation follows the methodology of Krieger et al (2022), however it uses seasonal instead of annual 95th percentiles. Doing so, we ensure that the calculation of GBSA in the hindcast is consistent with the derivation of observed GBSA in Krieger et al (2021). We perform the GBSA calculations individually for every member of the hindcast.…”

“…As an observational reference for storm activity in the German Bight, we make use of the time series of winter GBSA from Krieger et al (2021). The GBSA proxy in Krieger et al (2021) is defined as the standardized 95th seasonal (December-February, DJF) percentiles of geostrophic winds.…”

“…As an observational reference for storm activity in the German Bight, we make use of the time series of winter GBSA from Krieger et al (2021). The GBSA proxy in Krieger et al (2021) is defined as the standardized 95th seasonal (December-February, DJF) percentiles of geostrophic winds. These geostrophic wind speeds were originally calculated from three-hourly observations of mean sea-level pressure along the German Bight coast in Denmark, Germany, and the Netherlands, and cover the period of 1897/98-2017/18.…”

“…The climatology-based reference prediction is constructed from the climatological frequencies of observed GBSA (e.g., Wilks, 2011). Here, we draw on the definition of GBSA from Krieger et al (2021) which assumes an underlying Gaussian normal distribution.…”

Still normal? Contextualizing real-time data with long-term statistics to monitor anomalies and systematic changes in storm surge activity – Introduction of a prototype web tool storm surge monitor for the German coasts

“…Locally, water works may also play a role. To date, there is 720 no clear evidence suggesting a significant long-term change of storm activity in this region (Feser et al, 2015;Krieger et al, 2020;Krueger et al, 2019;Stendel et al, 2016;Weisse et al, 2012). It is likely that the observed long-term changes are largely related to the local mean sea level rise (e.g.…”