Doppler radar sees wind farms today

Posted at 8:33 AM on June 11, 2009 by Paul Huttner (4 Comments)

Sioux Falls NEXRAD clearly shows echoes from wind turbines along the Buffalo Ridge northeast of the radar site today. These echoes can be mistaken for showers or thunderstorms.

Wind farms in southern Minnesota and northern Iowa are clearly visible on both the Twin Cities and Sioux Falls doppler radars this morning. The radar echoes often mimic showers or even thunderstorms, and it takes a trained eye to differentiate between the two types of radar returns.

Usually the radar beam will shoot over the top of wind farms at distances from the radar site. But if conditions are right such as a when a temperature inversion is present, an atmospheric process called superrefraction bends the radar beam. The beam can follow the curvature of the earth for over a hunderd miles and bounce back off of the wind turbines.

Take a close look at the Twin Cities doppler image below. You can see the light green smudge of light rain showers north of Eau Claire and a little shower near Mankato. You can also see the bright yellow echoes throughout southern Minnesota and northern Iowa. Those are likely wind farms or some other man made tower. You can see how they could easily be mistaken for heavier showers or thunderstorms. Meterologists seek correlation from other data sources and ground truth to confirm the presence of rainfall.

You just never know what you're going to see on radar. Hiding among a few spotty showers today? Wind farms. Who knew?

PH

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Comments (4)

You have an uncanny knack for making weather interesting. Thanks for posting.

Posted by Adam | June 11, 2009 2:17 PM

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Adam:

Thanks for listening and surfing!

PH

Posted by Paul Huttner | June 11, 2009 5:13 PM

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How rare is this sort of thing? So the issue is not with the radar or the wind turbines, but both? Is this a problem in mountainous regions, or is it just the rotation of the wind turbine? Sorry lots of questions. Great story.

Posted by Evan | June 11, 2009 9:44 PM

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This is a fairly rare phenomenon, at least for this site. There are locations in southwestern Kansas (near Dodge City) and in Montana (near Great Falls) that see these somewhat more frequently.

In the interest of full disclosure, I should mention that I am currently employed by a wind farm developer and have had to address these concerns both from my employer and from local opposition to our construction and operations efforts. Given the typical motion of precipitation systems, the impact of wind farms on radar interpretation is not that significant, and certainly not something that the experienced professionals who issue radar-based warnings in the National Weather Service have problems with on a regular basis.

I had the pleasure of working with scientists at the University of Oklahoma when I was in graduate school who are studying ways to mitigate the effects of wind farms on radar, and they have made numerous breakthroughs in the past 3-4 years. Additionally, on the horizon is a new radar technology which will be capable of distinguishing much better between precipitation echoes and those from wind farms or other quasi-stationary ground clutter.

A simple Google search for 'wind turbine wsr-88d' yields numerous relevant results, and you can visit here to see some of the more recent advances. I believe Mr. Isom is still there, and his primary advisor, Dr. Bob Palmer, was on my graduate committee as well.

I apologize for my verbosity, but I found this article linked to on an anti-wind website and I wanted to make sure that others who may be led to the same place realize that the problem is significantly overblown.

Posted by Michael Morris | June 12, 2009 3:04 PM

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