Impacts of wind turbine farms on WSR-88D radars

In the United States, use of wind turbine farms to generate electricity has recently grown dramatically. When wind farms are close to weather radars, they can affect data quality and the performance of radar algorithms. Because of possible impacts to the NEXRAD Radar Program, the Radar Operations Center and the University of Oklahoma are studying wind farm radar returns to document current impacts and work on mitigation steps. This paper focuses on analysis of data from two WSR-88Ds: Dodge City, KS (KDDC), and Great Falls, MT (KTFX). KDDC has two wind farms within range: Northeast Wind Farm at 20-23 km range and Southwest Wind Farm at 37-40 km range. KTFX has only one wind farm, but it is at very close range (~6 km) and produces inter-turbine scatter and multi-trip echoes that can expand wind-farm-related-return to extended ranges. This paper documents if and how often wind farm returns are seen by the radars and the resulting impacts. Continuous climatologies have been collected in winter, spring, and summer months. Factors influencing how often the wind farms are “seen” by the radars are clutter filter type (map/all bins/notch width amount), wind speeds (better suppression for light winds), and vertical temperature stratification/beam propagation conditions (inversion/ducting is worst case). When wind farm radar returns are strong, there are obvious near-zero velocity returns, areas of high-speed and “disturbed” velocities, and enhanced spectrum widths. Some of the radar return is from the turbine towers (0 velocity) and some of the return is from the spinning turbine blades (at up to high wind speeds). Important impacts on radar algorithms and radar decision making are: mis-identification of precipitation echoes, false estimates of precipitation, false tornadic vortex and mesocyclone signatures, and incorrect storm cell identification and tracking.