Evaluation of high-resolution reanalyses for wind energy application in the North Sea and Baltic Sea

The exploitation of offshore wind energy is an essential part of the German energy transition (Energiewende). The planning of new offshore wind farms demands detailed information on wind conditions at turbine hub heights in the North Sea and Baltic Sea. High-resolution reanalyses which are based on state-of-the-art numerical weather prediction (NWP) models combined with data assimilation systems offer the required meteorological data which are suitable for climatological assessment.

The regional reanalysis COSMO-REA6 operated by Germany’s national meteorological service (Deutscher Wetterdienst, DWD) provides hourly data of 6 km horizontal resolution for 1995-2019/08 (Kaspar et al., 2020). Moreover, hourly data of 31 km horizontal resolution for 1950 to present are available from the global reanalysis ERA5 produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). DWD delivers reanalysis data and statistical evaluation results to Bundesamt für Seeschifffahrt und Hydrographie (BSH) in order to facilitate offshore site tenders. Data and a report were recently published as part of the tenders for 2021 (https://pinta.bsh.de/).

Here we present an evaluation of the 100 m wind speed and direction from COSMO-REA6 and ERA5 based on a comprehensive statistical analysis. On the reference side the FINO measurements (Research platforms in the North Sea and Baltic Sea, https://www.fino-offshore.de/en/index.html) from FINO1 and FINO2 are used. The FINO measurements are not used by the data assimilation schemes of the two reanalyses and therefore constitute independent reference data. The focus is on episodes prior to the installation of wind farms in the direct vicinity of the FINO platforms to avoid wake effects. The quality of the two reanalyses is compared to other state-of-the-art reanalyses and wind atlas data.

Reference:

Kaspar et al. (2020): Regional atmospheric reanalysis activities at Deutscher Wetterdienst: review of evaluation results and application examples with a focus on renewable energy, Adv. Sci. Res., 17, 115–128, https://doi.org/10.5194/asr-17-115-2020.