Articles | Volume 8, issue 11
Model description paper
18 Nov 2015
Model description paper |  | 18 Nov 2015

The Explicit Wake Parametrisation V1.0: a wind farm parametrisation in the mesoscale model WRF

P. J. H. Volker, J. Badger, A. N. Hahmann, and S. Ott

Abstract. We describe the theoretical basis, implementation, and validation of a new parametrisation that accounts for the effect of large offshore wind farms on the atmosphere and can be used in mesoscale and large-scale atmospheric models. This new parametrisation, referred to as the Explicit Wake Parametrisation (EWP), uses classical wake theory to describe the unresolved wake expansion. The EWP scheme is validated for a neutral atmospheric boundary layer against filtered in situ measurements from two meteorological masts situated a few kilometres away from the Danish offshore wind farm Horns Rev I. The simulated velocity deficit in the wake of the wind farm compares well to that observed in the measurements, and the velocity profile is qualitatively similar to that simulated with large eddy simulation models and from wind tunnel studies. At the same time, the validation process highlights the challenges in verifying such models with real observations.

Short summary
We introduce the Explicit Wake Parametrisation (EWP) for wind farms in mesoscale models that accounts for the wake expansion within a turbine-containing cell. In the EWP approach, turbulence kinetic energy (TKE) production results from changes in vertical shear. The velocity recovery compares well to mast data downstream of the offshore wind farm Horns Rev I. The vertical structure of the TKE and the velocity profile are qualitatively similar to that simulated with large eddy simulations.