Wind speed surplus in wind farm wakes quantified from satellite SAR and
mesoscale modeling
Abstract
Satellite SAR provides ocean surface wind fields at 10 m above sea
level. The objective is to investigate the capability of Synthetic
Aperture Radar (SAR) satellite StriX observations for mapping offshore
wind farm wakes. The focus is on the conditions under which an apparent
wind speed surplus is generated, measured in 48% of the 67 images
available. The results compare well to Sentinel-1 observations, showing
a 34% surplus rate during several years based on 1171 images. Three
wind speed surplus cases have been studied in detail using the mesoscale
Weather, Research, and Forecasting model (WRF) model with two wind farm
parametrizations. The SAR-based observations and WRF model compare for
most cases, though only when Turbulent Kinetic Energy (TKE) is included
in the wind farm parametrization. The TKE mixes higher momentum
downwards in a stable atmosphere, causing surface wind speed surplus
near the surface.