Fog Shows Amazing Details over North Sea Wind Farm
On 25 January 2016 at 12:45 UTC several photographs of the offshore wind farm Horns Rev 2 were taken by helicopter pilot Gitte Lundorff with an iPhone. A very shallow layer of fog covered the sea. The photos of the fog over the sea dramatically pictured the offshore wind farm wake. Researchers got together to investigate the atmospheric conditions at the time of the photos by analysing local meteorological observations and wind turbine information, satellite remote sensing and nearby radiosonde data. Two wake models and one mesoscale model were used to model the case and explain what was seen.
By Charlotte Bay Hasager, Ioanna Karagali, Patrick Volker and Søren Juhl Andersen Technical University of Denmark, Denmark and Nicolai Gayle Nygaard, DONG Energy, Denmark
What the Photos Showed
The fog in the photos is cold-water advection fog that originates from warm humid air flowing from the southwest over cold sea. In the wake of the operating wind turbines the fog is lifted up by swirling motion. The fog extends downwind from each wind turbine. Interestingly the wakes are relatively long and narrow. Meteorological observations and satellite data show the atmosphere to be stably stratified and this corresponds well to modest wake expansion. Furthermore it is noticed that the fog disperses downwind of the wind farm. This process is explained by additional mixture of warmer, drier air aloft.
