Wind Speed-Up in Wind Farm Wakes Quantified From Satellite SAR and Mesoscale Modeling

Satellite synthetic aperture radar (SAR) provides ocean surface wind fields at 10 m above sea level. The objective is to investigate the capability of SAR satellite StriX observations for mapping offshore wind farm wakes. The focus is on the conditions under which an apparent wind speed-up is generated, measured in 48% of the 67 images available. The results compare well to Sentinel-1 observations, showing a 34% wind speed-up rate during several years based on 1171 images. Three wind speed-up cases have been studied in detail using the mesoscale Weather, Research, and Forecasting (WRF) model with two wind farm parameterizations. At 10 m above sea level, the SAR-based observations and WRF model compare for most cases, though only when turbulent kinetic energy (TKE) is included in the wind farm parameterization. The TKE mixes higher momentum downward in a stable atmosphere, causing surface wind speed-up near the surface.