An in-depth observational and modeling analysis to explore long-range offshore wakes under different stability regimes

Abstract. As wind energy areas continue to be built out worldwide, it is increasingly important to understand the implications of long-range wind farm wakes on wind energy generation. While gross capacity factors can be estimated, the impacts of upstream wind farm wakes on downstream energy production, especially under stable conditions, are largely unknown. A clear understanding of marine atmospheric boundary layer (MABL) stability in offshore regions is still evolving, as continuous high-resolution thermodynamic profiles in the MABL are uncommon. Given the relationship between stability and long-range (>50 km) offshore wakes, it is increasingly important to reliably estimate stability conditions in offshore regions. With the lack of consistent observations in and around offshore wind farms, it is necessary to rely on mesoscale models such as the Weather Research and Forecasting (WRF) modeling system to estimate stability and wake lengths. For this work we test WRF's ability to reproduce wake effects and potential losses using flight data over wind farms in North Sea to evaluate its performance. As thermal stability is critical to understanding wake length, different metrics are evaluated to determine the best way to parameterize atmospheric stability from the WRF model. Results show that the bulk Richardson number derived from WRF can be used as a reliable metric to classify stability and that wake lengths are well represented under stable conditions.