Wind Farm Interference Showing Up on Doppler Radar
During the last several years, New York State has been a leader in supporting the growth of wind energy. As a result of this effort, there have been several "wind farm" projects developed across the region. In western New York, some of the bigger projects include the towns of Sheldon, Wethersfield, Eagle/Bliss in Wyoming county. These farms are located between 20 miles and 35 miles directly southeast of the Weather Surveillance Doppler Radar located at the National Weather Service office in Cheektowaga (KBUF) in northern Erie county. The towers are on top of ridges at elevations that exceed 1600 feet above mean sea level.
NWS Buffalo Doppler Radar
Unfortunately, the Wyoming county wind farms and their turbines are within the radar line of sight (RLOS) of the NWS doppler radar in Cheektowaga. The height of the wind turbine towers are about 265 feet above the ground, and the turbine blades extend an additional 125 feet. Hence, the top of the wind turbine rotors are about 400 feet above the ground in western and southern Wyoming County.
At this height, the rotating turbine blades of the wind farm impact the KBUF Doppler Radar beam. As you can see in the above image depicting most of western New York, the rotating wind turbines are having an affect on the radar beam.
A small part of the electromagnetic energy radar beam sent from the radar is reflected back by the rotating turbines. The radar processes this "returned energy" as an area of precipitation and plots it accordingly on the map. This contamination of the base reflectivity image as illustrated in the below image, has an effect on the radar algorithms used to estimate rainfall and to detect certain storm characteristics.
Learn more about how the Doppler Radar works here.
The rotating turbines also impact the velocity base data as you can see from the below image. This velocity data is used by radar operators and by a variety of algorithms in the radar's data processors to detect certain storm characteristics such as mesocyclones, tornado vortex signatures, and relative storm motion.
The KBUF doppler radar has a sophisticated clutter/interference removal scheme, however the scheme was designed to filter out spurious returned (reflected) energy that has little or no motion. This is effective for removing the returned signals from terrain, buildings, and other non-moving structures. Unfortunately, the radar sees the rotating wind turbine blades as targets having reflectivity and motion, hence processes these returns as weather.
Below is a one hour animation from the morning of June 8, 2009 between 730 am and 830 am EDT. As you can see, there is a persistent, stationary area of interference in Wyoming county from the wind turbine farm that appears on the KBUF base reflectivity radar image. In situations with slow moving or stationary areas of rainfall/thunderstorms, the wind farm interference could be misinterpreted as an area of heavy precipitation.
Wind turbine clutter or interference that shows up on the base reflectivity and velocity images produced by the doppler radar can have several impacts including:
Thunderstorm or winter storm characteristics could be masked or misinterpreted, reducing warning effectiveness in the vicinity of, and downrange of the wind farm.
False signatures contaminating Doppler velocity data in the vicinity and downrange of the wind energy facility could reduce forecaster's situational awarness, particularly during hazardous/severe weather events.
Data masking or contamination if thunderstorms develop over the wind farm may negatively impact warning effectiveness.
False precipitation estimates could negatively impact flash-flood warning effectiveness.
The best mitigation technique is to avoid locating wind turbines in the radar line of sight (RLOS) of the doppler radar. The National Weather Service is conducting an outreach program to ensure the wind energy industry and developers are aware of NWS Doppler Radar locations and the potential impacts on radar data. The NWS Radar Operations Center (ROC) works with these developers and suggests mitigation options to consider.
The NWS continues to learn about wind farm impacts on radars, weather forecast office operations, and other users where radars and wind farms are already in close proximity. Based on this information, the NWS will develop training materials for radar operators and weather forecasters on how to identify, mitigate, and partially work around wind turbine impacts during forecast and warning operations.
For much more information on how wind turbines impact doppler weather radar, check out the ROC website.
|National Weather Service
Weather Forecast Office Buffalo
587 Aero Drive
Buffalo, N.Y. 14225-1405
(716)565-0802 Climate and Forecast recordings
Page last modified: June 8, 2009