By now you’ve probably read about Wind speed trends over the contiguous USA by Pryor et al. (2009, in press, JGR)
There is also an Associated Press story which cites this as a “first-of-its-kind study, and suggests that average and peak wind speeds have been noticeably slowing since 1973, especially in the Midwest and the East.”
Steve McIntyre of Climate Audit takes the study to task, not only for its data and conclusions, but for the Shenanigans of Michael Mann and Gavin Schmidt when they try to backtrack post facto after giving independent interview to AP’s Seth Borenstein and suddenly finding themselves in disagreement over whether “climate change” is involved or not. Go team.
I’ll point out that measuring wind accurately over a long period is not easy, particularly because surface anemometers tend to be problematic by the nature of their mechanical design. Aerovanes are better, but still have some of the same issues.
There’s also issues with land use change around the sensor long term, which I’ll get to in a moment. But first, the instrumentation.
For the traditional anemometer, here are some issues I’ve identified:
- Cup anemometer accuracy is typically +/- 5% when new some are even less. It depends on cup size and how linear the detector is. Some are very non-linear at low speeds.
- Anemometers, being mechanical, age, just like automobile engines, they are only good for so many revs of the engine before stuff wears down, affecting accuracy.
- The most common aging problem of anemometers is dust/dirt accumulation in the bearings, which tends to slow them down. I used to have a collection of dead anemometers from the former California State Climatologist…the vast majority had sticky bearings. I’d use them as a prop then give them away to classrooms when I went out to give talks to kids.
- Aging tends to affect low wind speeds more, by virtue of friction and by the fact that the lions share of wind measurements are at low speeds below 10mph. 40+ mph winds are not an everyday occurrence in many parts of the world. Easy to see in in plot of wind speed distribution. Of course there are exceptions.
USHCN Climate Station, New England, North Dakota. Photo by Eric Gamberg
So, depending on how good the instrumentation is to start with, and how well it is maintained, we might see the slowdown in wind caused partly by long term sensor issues.
If maintenance of NWS/NOAA wind equipment used in this study is anything like what we’ve seen for the USHCN network, I think the answer will be self evident.
But there’s another issue- urbanization and the associated land use change.
On the Climate Audit thread, one of the commenters pointed out the wind record from the Great Blue Hill Observatory near Boston.
For those who don’t know, according to commenter MarkB “the Great Blue Hill observatory web site. GBH, is just south of Boston, USA, and supposedly has the longest continuous meteorology record in the country (1885-present). The observatory is at the top of the hill – 635 ft. – with a large woodland park all around. Wind speed is certainly down since 1980.”
Our own Evan Jones recently visited the Blue Hill Observatory for a TV interview on the surfacestations.org project by Mish Michaels at WBZ-TV in Boston. He pronounced it a CRN 3 by the way.
Here is a look at the observatory USHCN station. Click for large images direct from the Blue Hill website
The wind instruments are mounted on the old observatory tower:
See the graph of wind speed from the observatory below:
The graph brings some issues about urbanization to mind. The Boston area has been highly urbanized.
Urbanization could be roughing up the boundary layer.
Clearings, buildings, shopping malls, subdivisions, etc. create more friction and turbulence in lower level winds than say, open fields or vast swaths of forest top. More turbulence tends to inhibit smooth flow of wind, this decreasing the wind speed.
Granted Blue Hill is a bit higher than surrounding surface, but I think the the effect of increased turbulence and drag in the highly built up northeast will make an impact even at higher levels.
see this report by Zhang et al on urbanization impacts in China:
http://www.lapc.ac.cn/UpLoadFiles/File/2008meeting/dahui/zhangning.pdf
Urbanization leads to “heat island”, “dry island” and wind speed loss over urban area …
See the wind speed plots comparing urban/non urban on page 11
The wind speed slowdown due to urbanization has been known for quite some time. Here’s an older book on the subject:
page 1267:
Yet, the surface roughness of the city serves to reduce wind speeds…
and others:
http://ieeexplore.ieee.org/iel5/4534879/4534880/04535390.pdf?arnumber=4535390
Due to the friction and drag of buildings, there are wind speed losses over urban area in all cases (Fig.4). In summer, the reduce of wind speed can be 1.0 …
It seems then, since Blue Hill Observatory is in the middle of a large area of growth for the past 50 years, that some of this wind speed reduction related to land use change and urbanization would apply?
Have a look at this Google Earth 3D image showing the patchwork quilt of the terrain around the observatory. Note the may holes in the forest canopy around the observatory and the signs of ubanization. How much of that affects wind speed measured on the hill? How much of it was there 30, 40, 50 years ago?
I’d also like to find out when they last replaced/recalibrated their wind sensors. It is one of the sensors where detecting a problem is not always obvious, especially when they clog up with dust in the bearings.
When studies cite surface data from weather stations, it is always a good idea to look at land use/land change around the stations as well as the station instrumentation. Chances are you’ll find issues that may not have been considered.
John Galt (08:54:58) :
High-Altitude Wind Machines Could Power New York City . . .
. . .Personally, I think unmanned blimps tethered to the surface may be a better idea than kites because blimps will remain aloft when the wind isn’t blowing, whereas kits would fall back to earth.
That’s all we need, a whole bunch of wires running up to altitude for little and big airplanes to run into. But how could we argue against something that would reduce the need for carbon generating base load power plants to counter the unreliability of wind turbines and other renewable, sustainable, organic, and pristine sources. Maybe enough of them around New York could prevent the next 9-11.
.
I tried plotting an inverted CO2 (chemical) graph over the wind speed chart. Matches about as well as it does with temperature, i.e., don’t bother.
Our group has gone away from mechanical anemometers for our met measurements due to the problems with the mechanical ones.
We are current using 2-dimensional ultrasonic anemometers, such as this RM Young Model 85000. It lists for $1500 US dollars.
The Blue Hill picture dialogue for the microbarograph is in error stating that the chart is changed daily. If memory serves, the charts are good for five – seven days.
PhilK (11:26:32) :
Not a bad assumption. Nature is feeding only so much wind to a given place. Just like it wants to feed so much precipitation to any given area. Attempts at “precip enhancement” have often proven your assumption. So do idle wind generating farms.
Where it really got scary is the attempt at seeding out the Atlantic Hurricanes.
Maybe someone should dig up the why and what of the Hurricane Seeding that was called off.
Interesting this is considered a place for good history of weather conditions. The Blue Hills ski area is built right below the Observatory. See here picture here: http://www.skireport.com/massachusetts/bluehills/trailmap/?id=272
It was built in 1940’s. It has had many changes in number of trails (cutting of trees), buildings, etc. It also went into disrepair sometime in the last 10 years and was just reopened. More interestingly it was the first ski resort to use artificial snow making (I doubt that would affect temp, humidity, etc.) in late 1950’s.
Windmills which do not work properly it is because they have not been previously blessed by the dark soot prophet (i.e.: are not HIS brand)
The contrasts history has: From “atoms for peace” to “windmills of oblivion”
Windmills, the most poetic and futile creation of global warming imagination,
Windmills, the most pathetic and gruesome product of “climate change”,
Windmills, windmills, windmills to dry up winds, to ruin poetry, to cut sun into pieces, its light in shadows iterative ,
to kill birds, to break hearts with dissonance, to hasten old men’s departure
from an alien land they didn’t know when young,
to tear down the will, to chop soul in mindless and colorless patches,
Windmills, phantoms on deserted lands,
Windmills which ended love, which ended life.
As one who has competed in target shooting, outdoors, for nearly 25 years, I can tell you that the wind has not diminished in the midwest or Rocky Mountain region. It does change greatly from day to day, season to season. But less of it? Hardly.
I also have a hard time believing wind power varies as the cube of the speed. We are talking about a transfer of momentum, moving air mass to moving windmill blade. The efficiency of the turbine might increase with speed, especially at low speed, but the cube? You got some serious conservation of momentum and energy problems here. Drag increases at about the square of the velocity, but that’s a different animal.
Getting power down from 20,000 feet will require a very interesting conductor (pair). Not too many wires can support that length. So we wrap it in Kevlar and hope it doesn’t break? Gonna take a mighty big kite or balloon to support it. Hard to pass the laugh test.
John Galt (08:54:58) :High-Altitude Wind Machines Could Power New York City . . .. . .Personally, I think unmanned blimps tethered to the surface may be a better idea than kites because blimps will remain aloft when the wind isn’t blowing, whereas kits would fall back to earth.
Mike McMillan (11:52:53) :
That’s all we need, a whole bunch of wires running up to altitude for little and big airplanes to run into.
Probably safer than your roof mounted construction cranes.
“”” Retired Engineer (13:48:35) :
As one who has competed in target shooting, outdoors, for nearly 25 years, I can tell you that the wind has not diminished in the midwest or Rocky Mountain region. It does change greatly from day to day, season to season. But less of it? Hardly.
I also have a hard time believing wind power varies as the cube of the speed. We are talking about a transfer of momentum, moving air mass to moving windmill blade. The efficiency of the turbine might increase with speed, especially at low speed, but the cube? You got some serious conservation of momentum and energy problems here. Drag increases at about the square of the velocity, but that’s a different animal.
Getting power down from 20,000 feet will require a very interesting conductor (pair). Not too many wires can support that length. So we wrap it in Kevlar and hope it doesn’t break? Gonna take a mighty big kite or balloon to support it. Hard to pass the laugh test. “””
Maybe it’s time to take a refresher cours Retired.
You say that drag increases at about the square of the speed; in the simplest of models, no need for the about. So the “lift” and the “drag” are about in a constant ratio over the efficient range of the airfoil (propellor), so one would expect the lift to also increase as the square of the speed. That is the force being applied to the rotor, and if it moves some fraction (1-s) of the wind speed, where (s) is the prop slip, then the product of force and distance travelled in a certain time is the power. In water, prop slips are of the order of 10%, but I don’t know what it is in air, in any case the speed of the prop is some reasonably constant fraction of the wind speed. so that brings the power to the cuube of wind speed, over the efficient range of wind speeds, and rotor air foli design.
Change in wind speed over the oceans should be more relevant to global climate.
Retired Engineer (13:48:35) :
I think we’ve been through this before, but I think the answer is easy.
Each air molecule has kinetic energy proportional to 1/2 mv^2. (Just call it v^2) The number of molecules interacting with the windmill is proportional to v. Total energy interacting with the windmill is proportional to v^2 x v, or v^3. QED.
Anyone from Boston know what happened at Fenway when they built the sky boxes behind home plate? There was a significant drop off of home runs and a study showed that the sky boxes changed the wind patterns inside the ball park.
UWI – urban wind island. Gotta account for it.
Wind power increasing in a windmill as the cube of velocity is a consequence of simple high school physics–the kinetic energy of each unit mass of air is proportional to v-squared, and the rate at which mass hits the windmill is proportional to v. Thus, energy/time (power) is proportional to v-cubed if windmill efficiency is approximately constant with wind speed (which it is over small ranges).
Over larger ranges, efficiency increases as speed increases at low-ish velocities, but then begins to decrease at a high-ish velocity which is dependent on the design of the windmill.
Well, in Scotland it’s still as windy as hell.
I’ve always like the acoustic anemometers. By measuring differential air speed acoustically a few hundred times a second they can provide accurate three dimensional look at air flow. The devices are not subject to the inertia of anemometers.
Carbon nanotube conductors are more conductive than copper and stronger than steel. Unfortunately they are unavailable currently in industrial quantities.
Actually, IMHO, it makes sense that “climate change” would impact wind speed.
Here’s my reasoning; the climate is essentially a heat engine, and wind speed is a function, in some cases, of temperature differentials between the equator and the poles. Therefor, it seems to me that if the energy input (from the sun, TSI, magnetic, etc,) was declining, it would reduce average windspeeds. (however, in that case, this effect would, i think, be most noticeable in the last few years rather than long term)
Therefor, IMHO, it seems to me that a reduction in windspeed could better be explained by a cooling planet than a warming one.
Incidentally, the cynic in me wonders; is the shift of the AGW’ers from “Global Warming” to ‘Climate Change” calculated, so that a cooling planet, or any other climate phenomenon, fits the “Climate Change” scenario?
The Weather Channel is talking about this topic also in the “Climate & Green” section of their web site :
“Still, the study, which will be published in August in the peer-reviewed Journal of Geophysical Research… it raises a new side effect of global warming that hasn’t been looked into before.” (bold italics me)
http://climate.weather.com/articles/notsowindy061001.html
Retired Engineer– (I’m one too.) Re-read your old Fluids text. The energy does increase with the cube of velocity.
Should I joke about checking for an urban leeward effect by driving across a city and finding much higher windspeed than at weather stations, and slower windspeeds near the center?
Looking at the pictures around the hill, there appears to be alot of new growth hardwood forest. Perhaps much of the decline since 1980 can be attributed to the Bernoulli effect. It would be interested to see if the trend is the same for both winter and summer.
M. Simon (15:53:52) :
Carbon nanotube conductors are more conductive than copper and stronger than steel. Unfortunately they are unavailable currently in industrial quantities
Soon you will have nanocopper pigmented conductive plastics
http://www.giurfa.com
Absolutely, completely off topic. But worth a look: click
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