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« Josh 69 | Main | A copy of that cold winter forecast »

BBC on the atmosphere

BBC radio is running a three-part series on the atmosphere (H/T Phillip Bratby), presented by Gabrielle Walker, a former climate change editor at Nature. The most recent episode apparently features Chris Rapley, the boss of the Science Museum, discussing radiative physics. Phillip isn't sure he's got his facts right.

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Reader Comments (19)

Usual childish BBC rubbish I'm afraid. I do wish they would drop their ageism tactics and get some well rounded, intelligent presenters for this sort of thing or at least some who can ask the best questions.

Jan 21, 2011 at 2:14 PM | Unregistered Commenterstephen richards

Phillip was merely being polite in his statement, your grace.

The Irish term is "eejit".

Jan 21, 2011 at 2:27 PM | Unregistered CommenterDon Pablo de la Sierra

In other news, there appears to be a new problem with the greens' beloved birdshredder wind farms -- Wind turbines placed too close together (The Register)

Jan 21, 2011 at 3:06 PM | Unregistered CommenterJeroen B.

Rapley is now at UCL. His statement comes about 4 minutes in when he said words to the effect

Gases, mainly water vapour and carbon dioxide, absorb the IR and then re-emit it, ½ of that goes back to the surface and re-warms the surface

Rapley is supposed to be a physicist, but he obviously wasn’t taught about the most fundamental law of physics.

There is other garbage, but that is the worst example.

Jan 21, 2011 at 3:30 PM | Unregistered CommenterPhillip Bratby

It has been known for a long time that putting turbines too close together has three effects:
1 Power output at downwind turbines is reduced
2 Increased turbulence causes increased fatigue at downwind turbines
3 Increased turbulence causes increased noise from downwind turbines

Jan 21, 2011 at 3:31 PM | Unregistered CommenterPhillip Bratby

Is this wind turbine R&D being done on the tax payers dime (or 10p)?

Jan 21, 2011 at 3:38 PM | Unregistered CommenterKevin

Is this wind turbine R&D being done on the tax payers dime (or 10p)?

Yes, but it costs billions of pounds. Which, even in terms of American Billions, is a lot. But I fear it may be in terms of British billions.

Jan 21, 2011 at 3:51 PM | Unregistered CommenterDon Pablo de la Sierra

Question for Philip Bratby:

Hi Philip. I have what must seem a pretty naive question about wind farms.

When wave generators are set out at sea, the water behind the generator string is pretty calm because of the amount of energy taken from the water. So, the same must be true of wind passing through a wind farm. The down-wind air must be pretty calm. My question is, are any studies made of the effects of lack of wind turbulence on the environment down-wind when, pre-turbine, the environment - and the weather - was shaped by the turbulence?

Jan 21, 2011 at 4:07 PM | Unregistered CommenterPhilf


No, the turbine blades create a lot of downstream turbulence, just like downstream of an aeroplane wing. A turbine blade is just an aerofoil.

There are lots of videos of trubulence downstream of turbines. There is a superb photo of the turbulence downstream of the Horns Rev offshire wind farm at

Jan 21, 2011 at 4:24 PM | Unregistered CommenterPhillip Bratby

The down-wind air must be pretty calm. My question is, are any studies made of the effects of lack of wind turbulence on the environment down-wind when, pre-turbine, the environment - and the weather - was shaped by the turbulence?

The downwind side of a wind turbine is turbulent with gusty wind, yes some energy has been taken from it so there is a wind shadow but worse is the higher directional and speed variations which buffet the next turbine if it is too close. Effect is well known and extends to effect of hedges and trees.

Jan 21, 2011 at 4:25 PM | Unregistered CommenterBreath of fresh air

You're mixing up turbulence with vortex shedding. Turbulent flow only happens when you exceed the critical Reynolds Number of c. 2100. In the same was as the vortices from a 747 can cause a light plane to flip, so it is that they will cause unusual loading on subsequent windmill aerofoils which will operate at lower efficiency.

Jan 21, 2011 at 4:38 PM | Unregistered CommenterAlexander

If we are talking about turbulent or laminar flow, then yes. It is the large vortices, which can propagate many kilometres, which increase fatigue loading.

Jan 21, 2011 at 4:48 PM | Unregistered CommenterPhillip Bratby

Thank you Philip (and others) for your reply. I understand now. However, I still have a small niggle: as the wind must have imparted energy into the turbine, the turbulence created by the aerofoils cannot, surely, have the same energy as the original wind, otherwise the turbine would have been creating energy (my physics is rusty, but IIRC you can't create energy from nothing). So, there may be turbulence but it does not have the potential energy of the original wind flow, does it?

Jan 21, 2011 at 5:20 PM | Unregistered CommenterPhilf


A wind turbine will remove about 30% of the kinetic energy of the wind. So that well downstream of the turbine, when the mooth flow is re-established, the wind speed will be about sq root of 0.7 = 0.84 of the upstream speed (with no mixing from adjacent flow).

Jan 21, 2011 at 5:36 PM | Unregistered CommenterPhillip Bratby

Well perhaps the BBC's flagship (by wind of course) science programme Horizon should settle any doubts about this and other related issues.

I nearly chocked on my cornflakes when I heard the trailer on the Today programme this morning.

Jan 21, 2011 at 5:41 PM | Unregistered CommenterPaul

I appreciate the quick turnaround Philip. That's cleared up a lot for me. And I still hate the darned things!
When I saw your response I had a quick flashback to my days of studying AC power theory so when I saw the 0.7 value I thought you were going to say there is an RMS value in the wind ;-) (Would have been a little poetic of nature to do that.....)

Jan 21, 2011 at 5:43 PM | Unregistered CommenterPhilf

Jeroen B. @ Jan 21, 2011 at 3:06 PM

Excellent photo.

Take a gander at the change in albedo. Too many more of these things and we'll be wearing winter woolies here in Fiji, too.

Thanks for the link.

Jan 21, 2011 at 7:00 PM | Unregistered CommenterFijiDave

Oops, Jeroen B, my bad. Should be Phillip Bratby @ 4:24

(Don'tcha hate that?)

Jan 21, 2011 at 7:06 PM | Unregistered CommenterFijiDave

@Everyone: I'm happy I provoked a bit of good discussion

@Dave: no harm done ;-) I'll happily submerge to lurk again :)

Jan 21, 2011 at 7:53 PM | Unregistered CommenterJeroen B.

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