  The rapid growth of offshore wind energy requires accurate modeling of the
wind resource, which can be depleted by wind farm wakes. Turbulence dissipation
rate governs the accuracy of model predictions of hub-height wind speed and the
development and erosion of wakes. Here we assess the variability of turbulence
kinetic energy and dissipation rate using 13 months of observations from a
profiling lidar deployed on a platform off the Massachusetts coast. Offshore,
turbulence dissipation rate is 2 orders of magnitude smaller than onshore, with
a subtle diurnal cycle. Wind direction largely influences the annual cycle of
turbulence, with larger values in winter when the wind flows from the land, and
smaller values in summer, when the wind is mainly from open ocean. Because of
the weak turbulence, wind plant wakes will be stronger and persist farther
downwind in summer.
