Meteorological Impacts of Offshore Wind Turbines as Simulated in the Weather Research and Forecasting Model

Offshore wind energy projects are currently in development off the east coast of the United States and will likely influence the local meteorology of the region. Wind power production and other commercial uses in this area are related to atmospheric conditions, and so it is important to understand how future wind plants will change the local meteorology. We compared one year of simulations from the Weather Research and Forecasting model with and without wind farms incorporated, focusing on the lease area south of Massachusetts and Rhode Island. We assessed changes in wind speeds, 2 m temperature, surface heat flux, turbulent kinetic energy, and boundary layer height during different stability classifications and ambient wind speeds over the entire year. Because the wake behavior may be a function of boundary-layer stability, in this paper, we also present a machine learning algorithm to quantify the area and distance of the wake generated by the wind plant. This analysis enables us to identify the relationship between wake extent and boundary-layer height. Hub-height wind speed is reduced within and downwind of the wind plant, with the strongest impacts occurring during stable conditions and faster wind speeds. Wind speeds at 10 m increase within the wind plant area during stable conditions. Differences in 2 m temperatures and surface heat fluxes are small, but are largest during stable conditions and strong wind speeds. Turbulence kinetic energy (TKE) increases within the lease area with increasing wind speeds at both the surface and at hub height. At hub height, TKE increases do not depend on stability, but at the surface, TKE increases most during unstable conditions as the turbulence injected at hub height is mixed down to the surface. Boundary-layer heights increase within the wind plant, and decrease slightly downwind during stable conditions. Deeper boundary-layer heights, exceeding 100 m, tend to correlate with smaller wake areas and distances, though other factors likely also play a role in determining the extent of the wind farm wake.