Benchmarking model coupling and wind farm parameterizations for wind energy applications

Wind farm parameterizations (WFP) are used to simulate the effects of wind farms on the flow in mesoscale numerical weather models. In the past different WFP have been proposed, see the review by Fischereit et al. (2021). Two parameterizations, the WFP by Fitch et al. (2012) (FITCH) and Volker et al. (2012) (EWP), are frequently used and have been validated on a case-by-case basis. EWP accounts for a sub-grid scale wake expansion that is not considered in FITCH. FITCH, on the other hand, accounts for turbine-induced TKE, which is not included in EWP. Since then, new WFPs have been developed. Among others the further development of the EWP, EWP-LKE, by Garcia Santiago (2024) (https://orbit.dtu.dk/en/publications/mesoscale-modelling-of-large-wind-farms), which now includes a method to account for the turbulent kinetic energy (TKE) generation of the wind turbines, called latent TKE.  

Another challenge, besides the accurate representation of the wind farm effects in the mesoscale model, is to accurately simulate the meteorological background conditions. To better account for the exchange processes in the offshore environment between atmosphere, wave and ocean, atmosphere-wave and atmosphere-wave-ocean coupled models rather than standalone atmosphere-only models show potential. 

To improve our understanding of the contributions of both WFPs and model coupling to accurately account for the wind farm effect, we conduct several simulations with different settings for the German Bight. We compare the newly available WFPs against the exiting WFP for real cases and examine the effect of coupling atmosphere-wave (and –ocean) models on the simulation results. The simulation results are compared against open-access high-frequent measurements from the research aircraft flights during the X-Wakes campaign (Lampert et al., 2024). Additionally, measurements at the FINO masts will be used for profile validations.  

The period of interest covers one week between 23-31 July 2021, when several flights with two research aircrafts were performed during the X-Wakes campaign. The simulations are performed using an enhanced version of the COAWST modelling system (Warner et al., 2010), which includes the Weather, Research and Forecasting (WRF) model for the atmosphere, the Simulating WAves Nearshore (SWAN) model for the waves and the Regional Ocean Modelling System (ROMS) for the ocean. Enhancements to the existing modelling system include the Wave Boundary Layer model and additional wind farm parameterizations.  

This research was funded by the Horizon Europe Project DTWO (101146689).