The regional reanalysis COSMO-R6G2 as a successor to COSMO-REA6: evaluation for renewable energy applications

Abstract. The regional reanalysis COSMO-REA6 has frequently been used for applications in the energy sector, but there were also known deficits for some relevant features. A successor is currently produced and this manuscript provides a first initial technical validation, with a focus on those features. The dataset is available under an open data licence and is expected to be of interest for energy-related applications. Relevant meteorological variables for the renewable energy generation like Global Horizontal Irradiance (GHI, often also referred as global radiation) and wind speed at altitudes between 10 and 258 m of the new regional reanalysis COSMO-REA6 Generation 2 (COSMO-R6G2) by Deutscher Wetterdienst (DWD) are investigated with a focus on Germany using the regional reanalysis COSMO-REA6 as a benchmark. COSMO-R6G2 shows slightly lower values of GHI compared to COSMO-REA6, thus increasing the bias already present in COSMO-REA6. In terms of wind speed, comparisons to data from measurement masts (e.g. at sites Hamburg, Lindenberg and Karlsruhe) show good quality of COSMO-R6G2 in flatlands. As deficits in the representation of the daily cycle of wind speed at hub height were identified for COSMO-REA6, these characteristics were analysed in more detail. COSMO-R6G2 underestimates the night-time maximum over mountainous regions stronger than COSMO-REA6, but differences over low terrain are small and broadly comparable to COSMO-REA6. In summary, this initial assessment shows that users can use COSMO-R6G2 as an extended successor of COSMO-REA6, but should carefully consider the results of all quality assessments and known weaknesses of the COSMO-based datasets.