EGU2020-6829
https://doi.org/10.5194/egusphere-egu2020-6829
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

German Bight Storminess over the Last Century

Daniel Krieger1,2, Oliver Krueger2, Frauke Feser2, Ralf Weisse2, Birger Tinz3, and Hans von Storch2
Daniel Krieger et al.
  • 1Meteorological Institute, Universität Hamburg, Hamburg, Germany
  • 2Institute of Coastal Research, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany
  • 3Deutscher Wetterdienst, Hamburg, Germany

Assessing past storm activity provides valuable knowledge for economic and ecological sectors, such as the renewable energy sector, insurances, or health and safety. However, long time series of wind speed measurements are often not available as they are usually hampered by inhomogeneities due to changes in the surroundings of a measurement site, station relocations, and changes in the instrumentation. On the contrary, air pressure measurements provide mostly homogeneous time series as the air pressure is usually unaffected by such factors.

Therefore, we perform statistical analyses on historical pressure data measured at several locations within the German Bight (southeastern North Sea) between 1897 and 2018. We calculate geostrophic wind speeds from triplets of mean sea level pressure observations that form triangles over the German Bight. We then investigate the evolution of German Bight storminess from 1897 to 2018 through analyzing upper quantiles of geostrophic wind speeds, which act as a proxy for past storm activity. 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 North-East 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.

How to cite: Krieger, D., Krueger, O., Feser, F., Weisse, R., Tinz, B., and von Storch, H.: German Bight Storminess over the Last Century, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6829, https://doi.org/10.5194/egusphere-egu2020-6829, 2020

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Display material version 2 – uploaded on 04 May 2020, no comments
Added the names of the four reanalysis products that were used for validation.
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  • CC1: Comment on EGU2020-6829, Jan Wohland, 04 May 2020

    Dear Daniel Krieger & collaborators,

    thanks for sharing this interesting presentation!

    I wonder: Could this method be used for other quantiles of the wind speed PDFs? Or is it only suitable during high wind events (maybe because pressure gradients are large)?

    You mention that you compared with 4 reanalyses. Which ones did you use? 

    Best wishes,
    Jan (Wohland)

    • AC1: Reply to CC1, Oliver Krueger, 04 May 2020

      Dear Jan,

      the method has been generally evaluated in dx.doi.org/10.1175/2011JCLI3913.1, also for the median wind speed, which showed better correlations.

      The reanalyses were ERA5, ERA Interim, MERRA2, and CFSR.

      Kind regards,

      Oliver Krueger