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Posted at 10:30 AM ET, 07/15/2009

Can Wind Farms Change the Weather?

By Steve Tracton

* Summer Tries to Sizzle: Full Forecast | TWC's New Morning Show *


Large-scale wind farms, consisting of hundreds to thousands of wind turbines spread over large areas for generating electricity, are likely to play an increasingly important role in providing a climate-friendly source of energy. Unlike power plants that burn oil, coal or natural gas, wind power requires no fuel, emits no pollution and produces no carbon dioxide nor any other greenhouse gas.

The efficiency, effectiveness and economic value of wind power clearly depends critically on the weather, along with factors such as terrain, vegetation and building structures, which affect the speed, direction and variability of the wind striking the blades of wind turbines. But can wind farms, in turn, affect the weather? (Do you really think I'd be writing this post if the answer was "no"?)

Keep reading for more on wind farms and their potential to change weather...

The question might seem far-fetched at first. But think of wind farms, collectively, as huge butterflies in the realm of chaos theory, where a seemingly inconsequential event (e.g., a butterfly flapping its wings) can lead to consequential changes in the sequence of events that follow.

Researchers are investigating the potential for large wind farms in one region to alter weather patterns in another region downwind. Specifically, the turning of the wind mill propellers creates considerable turbulence, which mixes air up and down. The resulting bumpiness of the air could significantly influence winds at low levels of the atmosphere.

"If you have a couple of wind farms over a 10-kilometer patch in the Midwest, that's not going to make some kind of global impact on the weather," said University of Maryland atmospheric scientist Daniel Kirk-Davidoff in a recent Christian Science Monitor story. But if the whole Midwest "is somewhat roughened over a large area, then you could imagine having a large-scale impact on the atmosphere."

Kirk-Davidoff and his UMD colleague, Daniel Barrie, used a global general circulation model of the atmosphere (similar to the models used to predict climate change) to calculate the effects of blanketing the Midwest with a grid of interconnected wind farms with thousands of wind turbines. On average, the study found that wind speeds were lowered by 5.5-6.7 miles per hour immediately downwind. More significantly, the wind turbines caused large-scale disruptions of air currents, which rippled out like waves that appeared to trigger substantial changes in the development and track of storms over the North Atlantic.

The areal coverage and density of wind turbines in the study are admittedly unrealistic. Currently, the largest wind farm in the nation -- and world -- is the Horse Hollow Wind Energy Center in Taylor County, Texas, with 421 wind turbines in operation. However, ultra-large wind farms with thousands of turbines in especially wind-prone parts of Texas and the Midwest are considered within the realm of possibility.

The magnitude and degree of the impact of such wind farms would presumably be less than in the model simulation. But still the consequences, while unintended, could be significant, especially in situations involving storms such as major winter cyclones forming along a strong frontal zone. Ensemble forecasting has shown that even apparently innocuous changes in the low-level wind field can result in large uncertainties in the timing, strength and motion of major storms over a period of just a few days.

What remains unclear is how the impact of wind farms might compare to, for example, the effects of high-rise complexes or, for that matter, the influence of building a whole new city dominated by skyscrapers, such as that occurring at several locations across China. And yes, disturbances of the atmosphere originating in China can and frequently do impact weather systems affecting the United States in the matter of just a few days (to be discussed in a later post).

Wind farms may also result in important changes in local climatology, potentially impacting, for example, agricultural interests located within and immediately around areas encompassed by wind farms. The turbulence induced by the propellers of wind turbines mixes air along with the heat and moisture it contains -- the effects can spread for miles around. This is especially true at night when the disturbed airflow is not masked by the natural turbulence caused by solar heating.

Based on computer modeling, researchers at Duke and Princeton universities found that wind mill-generated turbulence raised pre-dawn surface temperatures by about four degrees and resulted in drier soil conditions. Presumably, the surface warmth was largely the result of the mixed air preventing the settling of cold air at the surface, while the dryness reflected increased evaporation by the wind of soil moisture. This is not dissimilar to the more familiar experience of a windy night keeping temperatures from falling as low as might otherwise be expected and also drying out pavement made wet by an evening shower.

By Steve Tracton  | July 15, 2009; 10:30 AM ET
Categories:  Climate Change, Tracton  
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No comments ?!?!?!?
I would say that reflects the appropriate level of interest :-)

Posted by: thornegp1 | July 15, 2009 12:33 PM | Report abuse

I can see changes but no more than the same effects from cutting down many square miles of trees, or planting many square miles of trees, or a city of skyscrapers as you pointed out in the article. DC is many degrees warmer than the surrounding suburbs due to lack of trees and the paved surfaces causing more heating by the sun. So change might occur with thousands of windmills especially to soil and other surface conditions.

The questions is whether this is a problem. If it means dryer soil then it would mean more irrigation. That might be an issue in CA where water is limited. But overall I think the few changes we see will be absorbed as we've somehow survived deforestation's effects, major city heat-island effects and other effects I think we could call minor.

And who knows, if there will be global effects they might not all be bad. Imaging 10s of thousands of windmills in America leading to the greening of the Sahara. Won't know unless we try. One thing I think is for sure, any changes will be minor compared with continuing to burn fossil fuels not to mention the issues with dependence on foreign energy.

Posted by: bevjims1 | July 15, 2009 12:39 PM | Report abuse

I find it quite interesting, unlike at least one other. It's smart to explore the interactions now before we get too far along (assuming we get smart and build more wind farms). Perhaps we can design wind farm distributions to actually benefit the local environment and do something smart for once.

Posted by: ronald_mccandless | July 15, 2009 12:46 PM | Report abuse

There are a few mega-wind farm projects in China that are slated to come online in the next two years. These will drwarf the largest US facility. One will have Phase 1 finished by next summer and is 7.6 times larger, eventually expanding to more than 54 times the size of Horse Hollow.

Posted by: johnnycomelately1 | July 15, 2009 1:13 PM | Report abuse

DId I actually read this right? There is a concern that windfarms will change weather BUT I have been told repeatedly that diesel exhaust, millions of gallons of jet fuel exhaust & the tens of thousand of tons of methane emitted by corporate farm animals has no significance in relation to weather change. Butterfly effect? Oh COME NOW! he skies of our great nation were not cleaner in the past 100 years than they were for the 3 days after 9/11, did that alter the "weather" down wind? NO!
This country burns million of BARRELS of petroleum daily and I am told by the non-environmentally concerned that we should not concern ourselves with cleaner air, BUT slow down the wind a percentage point or 10 and suddenly we have the making for a disaster? Someone has their priorities in the wrong order here!!
Whose anti-capitalist idea is this?

Posted by: misterfids | July 15, 2009 1:14 PM | Report abuse

You've got to be kidding me. Consider the volume of the atmosphere (not just what you can see). The sprinkling of wind turbines about the earth would be as significant as spitting in the ocean to change its salinity. By the way, two thirds of the earth are the oceans, and the main engine that drives our weather.

Posted by: spagnuolo | July 15, 2009 1:16 PM | Report abuse

There is no doubt there will be some effect - physics dictates it. What would enhance the study is a comparison of the effects on climate if the energy generated by the hypothetical windfarms was instead generated from traditional means. I am going to guess the effects will be much more severe, and it is this delta that is important, since in the end we need to get the energy from *somewhere*.

Posted by: peter44 | July 15, 2009 1:46 PM | Report abuse

Depends on how the lessening of surface winds due to the wind turbines affects the upper-air flow.

The effect may be to "meridionalize" the general flow pattern, leading to higher-amplitude Rossby waves, more Omega blocks and Rex blocks, more temperature extremes and more storminess here in the temperate zone. North-south mountain ranges such as the Rockies tend to cause waviness in the upper air, while east-west mountain ranges like the Alps and Himalayas tend to "anchor" pressure-fields over them. It's possible that wind diminution patterns due to large areras of wind turbines could have an effect similar to that of north-south oriented mountain ranges. I'm not sure how this all fits in with chaos theory.

Posted by: Bombo47jea | July 15, 2009 2:13 PM | Report abuse

Why not nuclear power?

No carbon dioxide, AND it works all the time. It works when there is no wind.

Would you want to power your hospital from wind power? Would you want to go into surgery knowing that the hospital was wind powered? Better hope the wind doesn't stop. ;)

Batter up Brian! Time to man up.

Mr. Q.

Posted by: Mr_Q | July 15, 2009 2:17 PM | Report abuse

Any effect wind turbines would have, even with a massive deployment that supplied all of U.S. electricity needs, is inconsequential compared to the effects of other human actions. A recent study published by the National Academy of Sciences this month says the atmospheric disturbance from such a large array of turbines would still only be equal to about 6% of all other disturbances. In fact, the reforestation of North America is causing a much greater increase in surface friction than any amount of wind turbines could ever cause. Large scale agriculture also significantly changes weather patterns – watering crops has been shown to have drastic effects on surface wind speeds by changing the interaction between the atmosphere and ground level humidity. Also, the NAS study suggests that the effect of a huge number of wind turbines would be to actually depress temperatures at higher latitudes, the areas that are currently experiencing the most human-induced warming, so we’re stopping global warming in two ways, not just one!

Posted by: chrismadison1 | July 15, 2009 3:32 PM | Report abuse

...think of wind farms, collectively, as huge butterflies in the realm of chaos theory, where a seemingly inconsequential event (e.g., a butterfly flapping its wings) can lead to consequential changes in the sequence of events that follow.
Well, then just imagine the consequential changes in the sequence of events that we have already caused! By extracting oil, gas, and coal from deep under the ground we are changing geologic strata and pressures leading to instability in geological formations. Burning the oil, gas and coal merely exacerbates changes in our global weather. We have already unleashed catastrophic consequences (with many more sure to come) for untold future species that are far worse than the impact of wind farms. I think we should build the wind farms where they are feasible and don't worry about it. The answer to our future energy needs lies in a combination of many different renewable technologies working together...not just fossil fuel.

Posted by: 42itus1 | July 15, 2009 3:37 PM | Report abuse

Some clarification: I'm not arguing for or against wind farms as an important player in alternative sources of energy. Rather, I'm just pointing out some issues that may or may not be worth considering in the bigger scheme of the many, many other factors that enter into the discussion of climate change. Actually, I strongly suspect that wind farms are small potatoes in the big picture of global climate change; however, they could be important in regionally specific climatology, such as surface temperatures and soil moisture as I described.

Aside from climate change per se, the wind farms nevertheless can affect the daily weather and weather forecasts in the spirit of the butterfly effect. The wind farms generate perturbations to the wind flow which can under some circumstances change the weather from what might otherwise have occurred - and do so over just a few days remotely form the actual location of the wind farms. Unless these perturbations are explicitly included in forecast models - not likely any time soon - they are just one more source of uncertainty (errors) that characterize all weather forecasts to varying degrees.

Posted by: SteveT-CapitalWeatherGang | July 15, 2009 4:49 PM | Report abuse

Can windmills change the climate?

No, but a computer programmer can make a model, sorta like the climate change hoax.

Posted by: stanlippmann | July 15, 2009 4:59 PM | Report abuse

Steve T-CapitalWeatherGang:

Thanks for the interesting post. But apparently some find the notion of simply asking a question to be unreasonable. Seems like people don't want to know.

Posted by: kempton | July 15, 2009 5:38 PM | Report abuse

Kind of related, Wind energry has definately had an effect on the weather in another interesting way.

Posted by: Brian-CapitalWeatherGang | July 15, 2009 5:52 PM | Report abuse

Similarly, see for another study on using surface roughness in models to simulate windfarms, and looking at surface temperature differences. Any energy solution at very large scale is likely to have some significant side-effects. (really, any resource use at large scale will have these: taking a few fish from the ocean and the ocean doesn't care. Feed 6 billion people fish from high on the food chain, and it will have effects)

My take-away would be a) use a basket of solutions, rather than depending on one single solution, and b) reduce overall energy and resource use with efficiency measures, reduced population growth, and changing consumption patterns.

Posted by: marcusmarcus | July 15, 2009 6:08 PM | Report abuse

Even if the global warming scam was real wind farms would not be a solution. That's because the wind stops blowing. Because of this fact the power companies have to have generating plant in a hot standby mode. That means the power plants are still burning fuel so that they can be ready to take over for a drop in the wind.
We have a power system that is working and not causing any real problems. Lots not spend millions of dollars to fix a non problem.

Posted by: nubeldorf1 | July 16, 2009 9:23 AM | Report abuse

I'm one of the authors of the study (Daniel Kirk-Davidoff). I want to echo a few of the other comments. I most certainly do *not* see the results of our study as an argument against deployment of wind turbines. All energy technologies have environmental impacts. I think one of the main lessons of the last 50 years of environmental science is that it behooves us to think as far in advance as possible about the impacts of human industry on the environment. This has born fruit, for example, in our successful effort to limit the destructive effect of ozone-destroying chemicals.

In the case of our study, I think there are two main lessons. First, we ought to consider the large scale effects of wind turbine installations on the wind resource itself- if we wanted to rely *very heavily* on wind power, we would need to think about spacing wind turbines out a bit more than if we thought they would have no large scale effect. Second, there appears to be some potential that if we built out the wind resource over a large spatial area, and if we made management decisions that caused the turbines to change their behavior simultaneously over that area, we could inadvertently cause some subtle changes in weather over the following days. This certainly doesn't mean we shouldn't build the turbines, but we would want to take these effects into account in order to avoid causing trouble for people downstream. I think studying these effects before we build the turbines is the best way to successfully manage this essential resource.

Thanks for your interest!

Posted by: dankd | July 16, 2009 11:47 AM | Report abuse

@ dankd

Thanks for your comments - right on.

To avoid possible misunderstanding, I was not referring to the possibility of purposeful weather modification as you appear to with the statement "if we made management decisions that caused the turbines to change their behavior simultaneously". Indeed I made a point of avoiding that issue.

I was referring only to possible changes of weather from that would otherwise occur in the absence of wind farms, exclusive of any purposeful manipulation of windmills. As mentioned, this is just another source of (more or less random) uncertainty in forecasts. It's an extremely dubious preposition that any artificial changes in the behavior of the turbines could produce some intentioned change in the weather. The uncertainty could never be reduced to the extent that would preclude invoking the law of unintended consequences.

Posted by: SteveT-CapitalWeatherGang | July 16, 2009 1:18 PM | Report abuse

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