https://orcid.org/0000-0001-8017-3136
Abstract
To accurately calculate the impact of renewables on power production in complex electric power grids, high-resolution and ideally seamless data within the planetary boundary layer are required. Therefore, the quality of different regional reanalyses and hindcasts is evaluated with respect to the representation of the planetery boundary layer and related sub-daily processes. On the one hand, high resolution regional reanalysis from the UERRA (UE-SMHI, UE-UKMO) and a similar project (COSMO-REA6) are considered. On the other hand, two hindcasts based on the COSMO-REA6 configuration are included in this study, i.e. a simulation with perfect boundaries and a simulation additionally utilizing spectral nudging. The focus of the evaluation is on measurements at four flux towers that are not part of any assimilation procedure. In this paper, we will show that the model’s quality depends on both the complete model system – assimilation method, resolution and physical parameterization – as well as on the performance measure. The daily cycle is best depicted by the hindcasts and even COSMO-REA6 hardly introduces spurious variability. UE-SMHI (3D-Var) suffers from spin-up in particular visible at the elevated levels, whereas the spin-up is damped in UE-UKMO (4D-Var). Investigation of atmospheric stability reveals that diurnal variation of stratification is for the most part well reproduced, but strong deficits were found for all COSMO simulations in reproducing strong stratification and corresponding wind speed gradients. Moreover, an overestimation of superadiabatic lapse rates and corresponding overly weak turbulent mixing is found for UE-UKMO. Furthermore, a combination of ramp statistics and contingency tables is utilized to detect a clear advantage of sophisticated assimilation systems over hindcasts. The evaluation framework presented underpins the importance of ramp statistics and vertical measurement profiles, especially with respect to assessing long-term simulations.
Acknowledgments
We thank the site operators at the MOL-RAO belonging to the German Weather Service, who delivered data from tower site Falkenberg. We thank to the weather mast group of the Meteorological Institute at the University of Hamburg, who delivered data from tower site Hamburg. We thank the group associated with the Cabauw tower and the related CESAR data base. We thank the IMK-TRO for providing Karlsruhe tower data. Without the extremely helpful comments and insight of the providers of observational data and reanalysis data, this paper would not exist. Furthermore, we thank Semjon Schimanke for carefully checking parts of the manuscript. In particular, we thank the reviewers for their incredible effort to improve the quality of the paper. The research work was funded by the Federal Ministry for Economic Affairs and Energy (ID: 0324006A). The authors acknowledge support from the Deutsche Klimarechenzentrum and the CLM community.
Disclosure statement
No potential conflict of interest was reported by the authors.
Supplementary material
Supplemental data for this article can be accessed here.