Wind Farm Interference Showing Up on Doppler Radar

National Weather Service ^ | 07-07-09 | National Weather Service

[blf1776]

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.

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

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.

[blf1776]

See web site for pictures

[blf1776]

This is the wind farm in Benton county Indiana. This is from the WLFI TV18 web site. www.wlfi.com

[Crazieman]

There are 5 wind farms around KICT (Wichita, KS) that screw with out radar. Very annoying.

[Logical me]

Interesting! As a former pilot, this might be a little concerning if we cannot rely in good weather information. Might find cancellations of takeoffs or landing at certain airports because of weather not supported. I’ve been against wind turbines from the start.

[GreyFriar]

What’s a few flash floods or tornados that weren’t picked up among friends. The dead people from those can be happy that they sacrificed their lives for ‘green energy from giant windmills.’

[Western Phil]

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

The interference from the Twin Groves Wind Farm east of Bloomington, Illinois seems to exist only when the blades are wet. Seems as though frost & heavy dew will sometimes cause reflections. There is no way for me to observe if the rotation has an effect, but I suspect it does. There is rain moving past just now (6:50 pm) and the farm is visible as stationary green on Weather Underground animated radar.

[Norman Conquest]

So on clear, dry days the turbines cause no problems. It’s only on stormy days that they’ll create false positive reports of dangerous storm activity? No problemo!

[blf1776]

The radar that I look at on WLFI TV18, almost always shows some interference from the wind farms. On a bright sunny day, I have seen what looks like a tornado on the radar. A small green storm with a bright red center. There is a small storm going through right now and most of the interference is gone.

[Freedom2specul8]

Thanks for the post..
Marked to read later

[Western Phil]

The radar that I look at on WLFI TV18, almost always shows some interference from the wind farms

I wonder if the blades contain metal. The ones on the Illinois Twin Groves Farm are fiberglass with no metal. Is there a windmill guru in the house?

[Western Phil]

I suspect most of the analysts know the farm is there and will likely discount the false information. At least one would hope.

[MediaMole]

While they know where the interference is, the appearance changes with the wind and weather. The reflections change as the windmills rotate or reorient to the wind.

It becomes very difficult when there are sporadic storms moving through an area.

zoom in on the radar below and look below the “r” in Beaver Dam. There is wind farm interference, but watch how it changes, appears and disappears.

http://radar.weather.gov/radar.php?rid=MKX&product=N0R&overlay=11101111&loop=yes

[Ole Okie]

I’ve been against wind turbines from the start.

You and me and Teddy Kennedy.

Oh, that's right. Teddy is just NIMBY.

[SuperLuminal]

Ah yes! The olde saw about “unintended consequences” bites another ass.

[blf1776]

From the TV18 weather guy.
http://blogs.wlfi.com/2009/07/01/wind-farms-show-up-on-live-doppler-18/

WIND FARMS SHOW UP ON LIVE DOPPLER 18…………
July 1st, 2009 at 4:16 pm by Chad Evans under Chad’s WLFI Weather Blog
I have had numerous questions recently as to why it seems to always be raining near Fowler, or why there continues to be a red blob over Benton County on Live Doppler 18:

National Weather Service radars & other television station radars are having the same issues as more & more wind farms are built.

There are 3 ways to combat this:

1. Decrease radar sensitivity, so the blob shows up less. However, this would mean that rainfall echoes would not be as detailed & would even be inaccurate. A heavy storm that should show up as red, could be only yellow on the radar. A pink spot indicating large hail might only be red or yellow, if sensitivity is decreased.

2. Tilt the radar beam upward to overshoot the wind farms. The Live Doppler beam is at the correct, standard height & a shift in the beam upward could overshoot any low-topped showers or t’storms near the radar or cause the data to be inaccurate by reflecting rain & hail data well up in the storm, not toward the surface. What is reflected toward the surface is what is likely reaching the ground.

3. Set up an “Exclusion Zone”. This would be built into the radar to basically skip northwest Tippecanoe, Benton & even far southwestern Newton counties so NO data shows up there. However, this would mean that these locations would have no coverage from our Live Doppler. Thus, that would never be a solution.

Obviously, there is no clear-cut remedy for this.

However, we do have a Doppler 18 Network of 4 other radars that are far enough away from that wind farm to prevent this data pollution from occurring.

Thus, I normally compare our data with Live Doppler 18 to our 4 other radars at National Weather Service Offices in Lincoln & Chicago, Illinois & North Webster & Indianapolis, Indiana. With these radars, I am able to determine whether wind farm interference is occurring or an actual t’storm is over central Benton County.

As more wind farms are constructed, potentially more blobs will develop on Live Doppler 18 over the next few years…………stay tuned………….

Here are other cool links that explain this phenomena:

http://www.meteorologynews.com/2009/04/13/windmills-interference-causing-problems-for-doppler-radar-signals/

http://www.erh.noaa.gov/buf/windfarm.htm

http://www.watertowndailytimes.com/article/20090624/NEWS03/306249964

[TXnMA]

Just as there are algorithms for subtracting out "ground clutter" signals near the doppler stations, it should be quite feasible to do the same for signal return from other stationary objects such as windmills...

FWIW, I note that the NOAA images all are "cranked up" and are showing massive ground clutter. I'd bet that simply turning on ground clutter suppression (subtraction) would reduce the windfarm effect significantly.

Personally, on my bookmarked WUnderground.com radar views, I keep ground clutter suppression "ON". The signals from actual dangerous weather are so strong that they are diminished hardly at all.

The simple act of animating ("looping") the radar displays makes it immediately obvious that the windfarm signals are stationary. As such, they are easy to ignore or discount.

IOW, this is much ado about nothing...

[blf1776]

One problem with your thoughts, the windmills are moving, it is not like a building. The radar display showing the farms changes, it comes and goes. The local weather guy has no answer.

[blf1776]

http://www.roc.noaa.gov/windfarm/how_turbines_impact_nexrad.asp

HOW WIND TURBINES IMPACT THE NEXRAD DOPPLER WEATHER RADAR

Wind farms can impact coherent (Doppler) radars in three ways if the turbine blades are moving and they are within the radar’s line of sight. If close enough (within a few kilometers) they can partially block a significant percentage of the beam and attenuate data down range of the wind farm. They can also reflect energy back to radar and appear as clutter on the radar image and contaminate the base reflectivity data. The base reflectivity data is used by radar algorithms to estimate rainfall and to detect certain storm characteristics. Finally, they can impact the velocity and spectrum width data, which are also used by radar operators and by a variety of algorithms in the radar’s data processors to detect certain storm characteristics, such as mesocyclones, relative storm motion, turbulence, etc. The WSR-88D has a sophisticated clutter removal scheme. Since weather is always in motion, the scheme was designed to filter returns that have essentially no or very low motion. This is effective for removing the returned signals from terrain, buildings, and other non-moving structures. Unfortunately, the radar sees rotating wind turbine blades as targets having reflectivity and motion, hence processes these returns as weather.

Wind farms at “extremely close” ranges to radars have all the impacts listed above and additional ones. Inter-turbine scatter and multi-trip/multi-path returns create false signals down-radial from the real wind farm echo regions. These down-radial returns have been observed for turbines located within 10 miles (16 km) of the radar, and can extend down radial for 25 miles (40 km) or further. In some cases the disturbed areas are large enough to cause additional forecaster confusion and distraction, and to affect forecasts and radar data (particularly Velocity Azimuth Display Wind Profile) assimilations into numerical models.

If wind turbines are in the main radar beam and within 600ft (183m) of radars (in the near field), damage to both the radar’s and turbines’ electrical components might occur, Turbines within 1 mile of a NEXRAD can prevent the radar’s beam from properly forming, thus causing significant radar estimation errors down range from the turbines.

In summary, WTC can have negative impacts on radar capabilities and products (radar imagery) over and near the wind energy facility. This reduction of useable radar data can also impact weather forecast and warning operations, DoD military operations, and FAA air traffic routing operations. Examples of these impacts are:

Thunderstorm or winter storm characteristics could be masked or misinterpreted, reducing warning effectiveness in the vicinity of and downrange of the wind energy facility.
False signatures contaminating Doppler velocity data in the vicinity and downrange of the wind energy facility could reduce forecasters’ situational awareness, particularly during hazardous/severe weather events.
Data masking or contamination if thunderstorms develop over the wind energy facility may negatively impact warning effectiveness.
False precipitation estimates could negatively impact flash-flood warning effectiveness.
Needless and expensive FAA aircraft re-routing from false returns due to WTC.

[TXnMA]

They are moving (rotating) -- hence the doppler return. OTOH, as far as position/location goes, they are stationary. If the problem is bad enough, it would be feasible to subtract the doppler return at that (fixed) location from that of the surrounding weather, thereby reducing its significance.

But, as I indicated, the windmillls aren't going anywhere; they are readily distinguished from moving weather on a time-based display. Your mind/eye does that automatically.

Like I said, no big deal...

[<1/1,000,000th%]

LOL!

So that’s where gobal warming comes from.