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From: bill.sloman on 1 Dec 2008 03:31 On 30 nov, 18:04, "John M." <john_howard_mor...(a)hotmail.co.uk> wrote: > On Nov 30, 4:28 pm, bill.slo...(a)ieee.org wrote: > > <big snip> > > > What I should have said here is that the radiation it does emit has > > the same intensity as a blackbody radiator would emit at that > > temperature. This follows from the second law of thermodydnamics - if > > it wasn't so a blob of CO2 surrounded by a blackbody would end up at a > > temperature other than that of the blackbody. > > Err... Isn't it the Zeroeth Law that assures temperature homegeneity? Who cares how the laws were numbered in your lessons. -- Bill Sloman, Nijmegen
From: Don Klipstein on 1 Dec 2008 03:38 In article <pan.2008.11.28.18.01.09.524861(a)REMOVETHISix.netcom.com>, Bill Ward wrote in part: >On Fri, 28 Nov 2008 05:54:19 -0800, bill.sloman wrote: > >> On 27 nov, 19:38, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >>> On Thu, 27 Nov 2008 06:55:09 -0800, bill.sloman wrote: >>> > On 27 nov, 02:31, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >>> >> On Wed, 26 Nov 2008 16:09:21 -0800, bill.sloman wrote: >>> >> > On 26 nov, 22:31, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >>> >> >> On Wed, 26 Nov 2008 04:43:36 -0800, bill.sloman wrote: >>> >> >> > On 26 nov, 06:57, Bill Ward <bw...(a)REMOVETHISix.netcom.com> >>> >> >> > wrote: >>> >> >> >> On Tue, 25 Nov 2008 18:15:34 -0800,bill.slomanwrote: >>> >> >> >> > On 25 nov, 22:31, Bill Ward <bw...(a)REMOVETHISix.netcom.com> >>> >> >> >> > wrote: >>> >> >> >> >> On Tue, 25 Nov 2008 11:42:55 -0800,bill.slomanwrote: >>> >> >> >> >> > On 25 nov, 17:50, Bill Ward >>> >> >> >> >> > <bw...(a)REMOVETHISix.netcom.com> wrote: >>> >> >> >> >> >> On Tue, 25 Nov 2008 03:14:09 -0800,bill.slomanwrote: >>> >> >> >> >> >> > On 25 nov, 09:47, Whata Fool <wh...(a)fool.ami> wrote: >>> >> >> >> >> >> >> bill.slo...(a)ieee.org wrote: >> >> <snip> >> >>> >> Now explain in your own words how traces of CO2 can affect Earth's >>> >> surface temperatures in the presence of a large excess of water. >>> >> Include the effects of latent heat convection, the near adiabatic >>> >> lapse rate through the troposphere, and the observation that the >>> >> effective radiating altitude and cloud tops are near each other. >>> >>> >> Can you do that, or are you just blowing smoke? >>> >>> >> <end repost> >>> >>> >> At this point, you're not only blowing smoke, you're looking a bit >>> >> dishonest with your snipping, then complaining. >>> >>> > I thought I'd covered that. In the near and middle infra-red both >>> > water and carbon dioxide have spectra that consist of a lot of narrow >>> > absorbtion lines - rotational fine structure around a few modes of >>> > vibration. >>> >>> > Only a few of these lines overlap, so to a first approximation the >>> > greenhouse effects of carbon dioxide and water are independent. Water >>> > doesn't mask CO2 absorbtions and an vice versa. >>> >>> > The situation gets more complicated when you look at the widths of the >>> > individual absorption lines. These are broader in the atmosphere than >>> > they are when looked at in pure sample of water vapour or carbon >>> > dioxide in the lab, which increases the greenhouse effect. >>> >>> > The mechanism of this "pressure broadening" is intermolecular >>> > collisions that coincide with the emission or absorbtion of a photon - >>> > this slightly changes the molecule doing the absorption/emission, >>> > slightly moving the position of the spectal line. >>> >>> > Polar molecules - like water and carbon dioxide - create more pressure >>> > broadening than non-polar molecules than oxygen and and nitrogen. They >>> > interact more strongly with the molecules they collide with - creating >>> > a bigger spectra shift - and the collision lasts longer. >>> >>> > So more carbon dioxide in the atmosphere makes water a more powerful >>> > green-house gas and vice versa. >>> >>> > Happy now? >>> >>> No, you just spewed the dogma again. I think the troposphere is there >>> because of convection lifting the surface energy up to the cloud tops, >>> maintaining a near adiabatic lapse rate. >> >> Convection becomes progressively less effective as the pressure drops - >> gas density decreases with pressure, which decreases the driving force you >> get from a given temperature difference in exactly the same proportion, >> and the quantity of heat being transported per unit volume is also >> reduced. > >So the gas is expanding. It's still rising, and the resistance is >decreased. Lift is roughly constant at least to 14000 ft, from personal >observation. It doesn't generally drop off linearly with altitude. > >>> Radiative transfer is blocked by GHG's, >> >> But only at the specific narrow bands of frequencies at which the GHG's >> absorb. > >Water vapor is pretty much broadband, except for the window around 9u. > >> As the pressure decreases and the water vapour contnet drops, >> these absorption lines get narrower, which facilitates radiative >> transfer. > >The radiative transfer is indeed facilitated above the cloud tops - >that's my point. Water vapor transfers the surface energy to those cloud >tops, not radiation. > >>>and plays little part below the tropopause. >> >> Evidence? > >Are you off on that "WV is not a GHG" kick again? > >>> Radiation models are thus largely irrelevant. >> >> So you claim, on the basis of a model that strikes me as seriously >> over-simplified. > >>> You completely ignored this part of my post: >>> >>> "Include the effects of latent heat convection, the near adiabatic >>> lapse rate through the troposphere, and the observation that the >>> effective radiating altitude and cloud tops are near each other." >> >> Scarcely. I was going to some trouble to point out that it was >> oversimplified. > >Funny, I'm pointing out yours is overcomplicated, worrying about >radiative transfer through the lower troposphere, which is basically >translucent to LWIR, and ruled by convection. > >> You've got a steady heat flux going up through a column of air whose >> density decreases with height, and you are assuming that the same heat >> transfer mechanism that works at ground level is working equally >> effectively when the pressure has halved, convection has been cut to 255 >> of ground level value, and all the latent heat being carried up by water >> vapour has already condensed out. > >Until you can show different, yes. It's not just the energy that's >moving, it's the column of air itself. When you lift water vapor, you're >transferring heat. A lot of heat, relative to radiation. >Below cloud base, how do you think the effectiveness is reduced? If the >heat left the surface, where can it go but up? Lift (upward velocity) is >relatively constant in a thermal, and often increases just under cloud >base. > >Above cloud base, you can see externally the billowing from release of >latent heat, and internally, (not recommended), you can feel it quite >convincingly in the form of turbulence. I see plenty of clouds that are stratiform from bottom to top - and I mean besides "fog-like low stratus". Most of those are formed from water vapor in air that ascended from lower altitudes not underneath but dozens or hundreds of miles away somewhere warmer. <SNIP everything after the point that I responded to here> - Don Klipstein (don(a)misty.com)
From: Don Klipstein on 1 Dec 2008 03:45 In <bde209ce-3792-4e1b-9474-f83210132440(a)3g2000yqs.googlegroups.com>, bill.sloman(a)ieee.org wrote: >On 28 nov, 19:01, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >> On Fri, 28 Nov 2008 05:54:19 -0800, bill.sloman wrote: >> > On 27 nov, 19:38, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >> >> On Thu, 27 Nov 2008 06:55:09 -0800, bill.sloman wrote: >> >> > On 27 nov, 02:31, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >> >> >> On Wed, 26 Nov 2008 16:09:21 -0800, bill.sloman wrote: >> >> >> > On 26 nov, 22:31, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >> >> >> >> On Wed, 26 Nov 2008 04:43:36 -0800, bill.sloman wrote: >> >> >> >> > On 26 nov, 06:57, Bill Ward <bw...(a)REMOVETHISix.netcom.com> >> >> >> >> > wrote: >> >> >> >> >> On Tue, 25 Nov 2008 18:15:34 -0800,bill.slomanwrote: >> >> >> >> >> > On 25 nov, 22:31, Bill Ward <bw...(a)REMOVETHISix.netcom.com> >> >> >> >> >> > wrote: >> >> >> >> >> >> On Tue, 25 Nov 2008 11:42:55 -0800,bill.slomanwrote: >> >> >> >> >> >> > On 25 nov, 17:50, Bill Ward >> >> >> >> >> >> > <bw...(a)REMOVETHISix.netcom.com> wrote: >> >> >> >> >> >> >> On Tue, 25 Nov 2008 03:14:09 -0800,bill.slomanwrote: >> >> >> >> >> >> >> > On 25 nov, 09:47, Whata Fool <wh...(a)fool.ami> wrote: >> >> >> >> >> >> >> >> bill.slo...(a)ieee.org �wrote: >> >> > <snip> >> >> >> >> Now explain in your own words how traces of CO2 can affect Earth's >> >> >> surface temperatures in the presence of a large excess of water. >> >> >> �Include the effects of latent heat convection, the near adiabatic >> >> >> lapse rate through the troposphere, and the observation that the >> >> >> effective radiating altitude and cloud tops are near each other. >> >> >> >> Can you do that, or are you just blowing smoke? >> >> >> >> <end repost> >> >> >> >> At this point, you're not only blowing smoke, you're looking a bit >> >> >> dishonest with your snipping, then complaining. >> >> >> > I thought I'd covered that. In the near and middle infra-red both >> >> > water and carbon dioxide have spectra that consist of a lot of narrow >> >> > absorbtion lines - rotational fine structure around a few modes of >> >> > vibration. >> >> >> > Only a few of these lines overlap, so to a first approximation the >> >> > greenhouse effects of carbon dioxide and water are independent. Water >> >> > doesn't mask CO2 absorbtions and an vice versa. >> >> >> > The situation gets more complicated when you look at the widths of the >> >> > individual absorption lines. These are broader in the atmosphere than >> >> > they are when looked at in pure sample of water vapour or carbon >> >> > dioxide in the lab, which increases the greenhouse effect. >> >> >> > The mechanism of this "pressure broadening" is intermolecular >> >> > collisions that coincide with the emission or absorbtion of a photon - >> >> > this slightly changes the molecule doing the absorption/emission, >> >> > slightly moving the position of the spectal line. >> >> >> > Polar molecules - like water and carbon dioxide - create more pressure >> >> > broadening than non-polar molecules than oxygen and and nitrogen. They >> >> > interact more strongly with the molecules they collide with - creating >> >> > a bigger spectra shift - and the collision lasts longer. >> >> >> > So more carbon dioxide in the atmosphere makes water a more powerful >> >> > green-house gas and vice versa. >> >> >> > Happy now? >> >> >> No, you just spewed the dogma again. �I think the troposphere is there >> >> because of convection lifting the surface energy up to the cloud tops, >> >> maintaining a near adiabatic lapse rate. >> >> > Convection becomes progressively less effective as the pressure drops - >> > gas density decreases with pressure, which decreases the driving force you >> > get from a given temperature difference in exactly the same proportion, >> > and the quantity of heat being transported per unit volume is also >> > reduced. >> >> So the gas is expanding. �It's still rising, and the resistance is >> decreased. �Lift is roughly constant at least to 14000 ft, from personal >> observation. It doesn't generally drop off linearly with altitude. > >But it is less dense, so it's transporting less heat. > >> >>�Radiative transfer is blocked by GHG's, >> >> > But only at the specific narrow bands of frequencies at which the GHG's >> > absorb. >> >> Water vapor is pretty much broadband, except for the window around 9u. > >Only if your spectrometer can't resolve the rotational fine structure. >And the partial pressure of water vapour drops off very rapidly with >altitude because the any water vapour is condensing as the air >temperature falls, so there's very little of it left to do any >absorbtion or pressure broadening by the time you get to the >tropopause. > >Water vapour can only be an effective greenhouse gas in tolerably warm >air, and the infra-red frequencies that water vapour blocks gets a >free run to outer space well below the tropopause. > >The earth radiates as if it's temperature - averaged over all >radiation wavelengths - is -14C which is a lot warmer than the -55C of >the mid-latitude tropopause, and in fact the equivalent radiating >level is about 6 km above ground, about half-way through the >troposphere. > >This also seems to coincide with the global average cloud top height > >http://cat.inist.fr/?aModele=afficheN&cpsidt=19121191 <SNIP beyond that point> Cloud top altitude actually has a very wide diversity. I find it fairly common to see plenty of cloudiness (with bottom at least 1500 feet) having top around/under 6,000 feet, which is below roughly 82% of the mass of the atmosphere. Clouds as high as 60,000 feet are a bit common in and near the tropics, and that is above roughly 89% of the mass of the atmosphere. - Don Klipstein (don(a)misty.com)
From: bill.sloman on 1 Dec 2008 03:55 On 30 nov, 22:41, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: > On Sun, 30 Nov 2008 07:28:18 -0800,bill.slomanwrote: > > On 29 nov, 21:38, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: > >> On Sat, 29 Nov 2008 09:58:21 -0800,bill.slomanwrote: > >> > On 28 nov, 16:55, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: > >> >> On Fri, 28 Nov 2008 02:26:40 -0800,bill.slomanwrote: > >> >> > On 27 nov, 23:02, Whata Fool <wh...(a)fool.ami> wrote: > >> >> >> bill.slo...(a)ieee.org wrote: > >> >> >> >On 27 nov, 02:59, Whata Fool <wh...(a)fool.ami> wrote: > >> >> >> >> "DeadFrog" <DeadF...(a)Virgin.net> wrote: > > >> >> >> >> >"Whata Fool" <wh...(a)fool.ami> wrote in message > >> >> >> >> >news:fdeni4p8pptdaacn58utfjlehk9jcbfmff(a)4ax.com... > >> >> >> >> >> bill.slo...(a)ieee.org wrote: <snip> > >> >> That needs a little explanation. CO2 gas is not a BB radiator. At > >> >> the temperatures in question, the 15u band should be the only > >> >> radiation it can absorb or emit. How do you come to the conclusion > >> >> it emits in a -55C BB spectrum? Do you have a link supporting that? > > >> > I didn't say that it emitted a black body spectrum. It emits the same > >> > spectrum as any volume of carbon dioxide at 218K would, which is > >> > different from the spectrum emitted by warmer carbon dioxide. > > > What I should have said here is that the radiation it does emit has the > > same intensity as a blackbody radiator would emit at that temperature. > > > This follows from the second law of thermodydnamics - if it wasn't so a > > blob of CO2 surrounded by a blackbody would end up at a temperature other > > than that of the blackbody. > > >> You said, "a spectrum that matches the roughly -55C temperature of the > >> bulk of the stratosphere", not a "218K CO2 spectrum". > > > Same thing. > > Isn't the CO2 absorption/emission spectrum a band, not a BB distribution? > In part of your previous post (which you snipped) you linked to this: > > http://www.wag.caltech.edu/home/jang/genchem/ir_img7.gif > > It doesn't look like a BB to me. Are you having trouble keeping your > stories straight again? You seem to be having some trouble understanding what is going on. Carbon dioxide has two stretching vibrational modes in the infra-red - the symmetrical stretch doesn't emit or absorb (because it is symetrical). The aysymmetircal stretch at 5u and the bending mode at 15u are both active, and both will have a rotational fine structure (I'd expect to see P,Q and R branches, but can't guarantee it). The relative intensities of the peaks of the active absobtion lines will be the same as the corresponding wavelengths of infra-red emitted from a blackbody at the same temperature. > >> > This follows from the second law of thermodynamics. The fact that the > >> > 218K spectrum is going to be different from the spectrum emitted by a > >> > warmer lump of gas depends on the proposition that the numbers of > >> > molecules occupying higher energy vibrational and rotational quantum > >> > states changes with temperature, and it is this distribution across > >> > the accessible quantised energy levels that dictates the shape of the > >> > emission spectrum. > > The "lump" would need to absorb and emit just enough to stay in thermal > equilibrium. Why would the general spectrum suddenly change? What you are > saying doesn't make sense to me. Please explain. Why do you think that there is a "general spectrum" and why do you think it has to "suddenly change"? > > >> Outside the 15u band? How much difference is there between the energy > >> in the spectra at the two temperatures? > > >http://en.wikipedia.org/wiki/Black_body > > > work it out for yourself. > > Let me rephrase: I don't think there's a significant difference. Show > why you think there is. Start by showing why you think it's a BB > distribution. I very explicitly said that it wasn't a broad-band distribution. The second law of thermodynamics - heat can only flow from a hotter body to a colder body - dictates that those wavelengths that CO2 emits and absorbs have the same intensity as the corresponding slices out of blackbody distribution that you get from a blackbody at the same temperature. And why do you think that the 5u band is turned off when the CO2 gets cold? It will be less intense than it is at higher temperatures - looking at it from the emission point of view, the proportion of intemolecular collisions that have enough energy to excite the the asymmetric stretch is reduced when the gas gets cold - but there's no on/off switch. -- Bill Sloman, Nijmegen
From: Don Klipstein on 1 Dec 2008 03:59
In <pan.2008.11.29.04.28.21.555150(a)REMOVETHISix.netcom.com>, Bill Ward said: >On Fri, 28 Nov 2008 17:38:49 -0800, bill.sloman wrote: > >> On 28 nov, 19:01, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >>> On Fri, 28 Nov 2008 05:54:19 -0800, bill.sloman wrote: >>>> On 27 nov, 19:38, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >>>>> On Thu, 27 Nov 2008 06:55:09 -0800, bill.sloman wrote: <SNIP stuff already said more than 6 times> >>>>>> I thought I'd covered that. In the near and middle infra-red both >>>>>> water and carbon dioxide have spectra that consist of a lot of >>>>>> narrow absorbtion lines - rotational fine structure around a few >>>>>> modes of vibration. >>> >>>>>> Only a few of these lines overlap, so to a first approximation the >>>>>> greenhouse effects of carbon dioxide and water are independent. >>>>>> Water doesn't mask CO2 absorbtions and an vice versa. >>> >>>>>> The situation gets more complicated when you look at the widths of >>>>>> the individual absorption lines. These are broader in the >>>>>> atmosphere than they are when looked at in pure sample of water >>>>>> vapour or carbon dioxide in the lab, which increases the greenhouse >>>>>> effect. >>> >>>>>> The mechanism of this "pressure broadening" is intermolecular >>>>>> collisions that coincide with the emission or absorbtion of a >>>>>> photon - this slightly changes the molecule doing the >>>>>> absorption/emission, slightly moving the position of the spectal >>>>>> line. >>> >>>>>> Polar molecules - like water and carbon dioxide - create more >>>>>> pressure broadening than non-polar molecules than oxygen and and >>>>>> nitrogen. They interact more strongly with the molecules they >>>>>> collide with - creating a bigger spectra shift - and the collision >>>>>> lasts longer. >>> >>>>>> So more carbon dioxide in the atmosphere makes water a more >>>>>> powerful green-house gas and vice versa. >>> >>>>>> Happy now? >>> >>>>> No, you just spewed the dogma again. I think the troposphere is >>>>> there because of convection lifting the surface energy up to the >>>>> cloud tops, maintaining a near adiabatic lapse rate. >>> >>>> Convection becomes progressively less effective as the pressure drops >>>> - gas density decreases with pressure, which decreases the driving >>>> force you get from a given temperature difference in exactly the same >>>> proportion, and the quantity of heat being transported per unit volume >>>> is also reduced. >>> >>> So the gas is expanding. It's still rising, and the resistance is >>> decreased. Lift is roughly constant at least to 14000 ft, from >>> personal observation. It doesn't generally drop off linearly with >>> altitude. >> >> But it is less dense, so it's transporting less heat. > >Energy is conserved. Where did the latent heat go, if not up? It's >carried by convection to the cloud top, and radiates away. Not all of it (latent or the majority otherwise) does. And greenhouse gases above the cloudtop will return to the cloud some of the cloud's thermal radiation. And what goes up usually must go down - especially air. The air rising through the cloud mass of a Nor'Easter will descend somewhere. > The whole >notion of somehow "trapping" energy in the atmosphere seems ludicrous. >It's either sensible heat, latent heat, or radiation. It doesn't just >disappear. It accumulates until radiator temperatures get sufficient to have radiative outgo to outer space match radiative income from the Sun. <SNIP from here> - Don Klipstein (don(a)misty.com) |