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From: Don Klipstein on 19 Dec 2008 22:20 In article <0ikpj41k4v8j7oikln12bjsk3dg44hrc0g(a)4ax.com>, Whata Fool wrote: >don(a)manx.misty.com (Don Klipstein) wrote: > >>In article <pan.2008.11.29.05.43.32.198332(a)REMOVETHISix.netcom.com>, Bill >>Ward wrote in part: >[snip] >>>Just keep in mind you can't actually heat a hot source from a cold >>>target. All you can do is slow the rate of cooling of the hot source. The >>>sky is cold, the surface is hot. >> >> GHGs will slow the cooling by making outgoing radiation from the surface >>absorbed at a lower, warmer level, which radiates half its radiation >>downward. >[snip] >> - Don Klipstein (don(a)misty.com) > > > Do you mean "cooling of the surface", meaning the solid or >liquid surface rather than the lower atmosphere? > > > If N2 doesn't radiate much in longwave, then any cooling is >faster than almost no cooling at all. > > All the atmospheric radiation physics is interesting, but we >have a few men claiming life on Earth could suffer displacement or >death if the increased CO2 causes a slower cooling of the lower >atmosphere. > > If there was no radiation cooling of the lower atmosphere >without any GHGs at all, is there some mystical way that more GHGs >can cause slower cooling than 100 years ago. The lowest part of the atmosphere does get cooled by the surface. And GHGs in the lower atmosphere have their radiation going towards the surface, in addition to all of the radiation that the surface would have received without them. And GHGs in the lower atmosphere don't merely cool - they receive radiation from the surface and can be warmed. > I am well aware of the temperature records and averaging, >but physics works the same way all the time, and with zero GHGs >equaling zero cooling, doesn't GHGs mean cooling, and more GHGs >mean more cooling, and less GHGs mean less cooling. Except for GHGs making the surface warmer than otherwise by adding radiation to that already heading to the surface, and GHGs in the lower atmosphere can experience radiational warming from the surface. > Statements that are not consistent are confusing. - Don Klipstein (don(a)misty.com)
From: Whata Fool on 19 Dec 2008 23:27 don(a)manx.misty.com (Don Klipstein) wrote: >In article <0ikpj41k4v8j7oikln12bjsk3dg44hrc0g(a)4ax.com>, Whata Fool wrote: >>don(a)manx.misty.com (Don Klipstein) wrote: >> >>>In article <pan.2008.11.29.05.43.32.198332(a)REMOVETHISix.netcom.com>, Bill >>>Ward wrote in part: >>[snip] >>>>Just keep in mind you can't actually heat a hot source from a cold >>>>target. All you can do is slow the rate of cooling of the hot source. The >>>>sky is cold, the surface is hot. >>> >>> GHGs will slow the cooling by making outgoing radiation from the surface >>>absorbed at a lower, warmer level, which radiates half its radiation >>>downward. >>[snip] >>> - Don Klipstein (don(a)misty.com) >> >> >> Do you mean "cooling of the surface", meaning the solid or >>liquid surface rather than the lower atmosphere? >> >> >> If N2 doesn't radiate much in longwave, then any cooling is >>faster than almost no cooling at all. >> >> All the atmospheric radiation physics is interesting, but we >>have a few men claiming life on Earth could suffer displacement or >>death if the increased CO2 causes a slower cooling of the lower >>atmosphere. >> >> If there was no radiation cooling of the lower atmosphere >>without any GHGs at all, is there some mystical way that more GHGs >>can cause slower cooling than 100 years ago. > > The lowest part of the atmosphere does get cooled by the surface. >And GHGs in the lower atmosphere have their radiation going towards the >surface, in addition to all of the radiation that the surface would have >received without them. > > And GHGs in the lower atmosphere don't merely cool - they receive >radiation from the surface and can be warmed. There is the normal warming in daytime even from IR through clouds, but any major warming always comes with wind shift. There is a constant loss of energy to space from the atmosphere, the atmosphere is never a source of energy as some writings seem to suggest. >> I am well aware of the temperature records and averaging, >>but physics works the same way all the time, and with zero GHGs >>equaling zero cooling, doesn't GHGs mean cooling, and more GHGs >>mean more cooling, and less GHGs mean less cooling. > > Except for GHGs making the surface warmer than otherwise by adding >radiation to that already heading to the surface, and GHGs in the lower >atmosphere can experience radiational warming from the surface. > >> Statements that are not consistent are confusing. > > - Don Klipstein (don(a)misty.com) I don't think you are really making the comparison of the present Earth and an Earth with an N2 and O2 atmosphere no GHGs or water. It is even bizarre that anyone would claim the atmosphere could be cooled more than at present by interaction with the surface, and that is what you seem to be claiming. I agree that GHGs in the lower atmosphere can and do return part of the surface radiation back to the surface, but even with clouds, there is cooling at night if the wind is not bringing warmer air. I don't understand the obsession with GHG theory, it is partially right but saying that the Earth would be 33 degrees colder without GHGs is a fallacy that might lead to the spectre of additional CO2 cooling the Earth instead of warming it. The big fallacy is in the big change in the station locations used in the averaging, there should be no confidence at all in the results of the change of dozens or hundreds of locations used, even if anomalies are used because some locations have different ranges of diurnal temperatures, and that can have an effect on the minimum temperature anomaly. I suggest that a study of only maximum daily temperatures of only the same locations might show something entirely different.
From: Don Klipstein on 19 Dec 2008 23:52 In article <pan.2008.12.08.09.21.16.182224(a)REMOVETHISix.netcom.com>, Bill Ward wrote: >On Mon, 08 Dec 2008 04:30:44 +0000, Don Klipstein wrote: > >> In article <pan.2008.11.29.05.43.32.198332(a)REMOVETHISix.netcom.com>, Bill >> Ward wrote in part: >>>On Fri, 28 Nov 2008 19:25:22 -0800, bill.sloman wrote: >>> >>>> On 27 nov, 20:50, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >>>>> On Thu, 27 Nov 2008 07:50:47 -0800, bill.sloman wrote: >>>>> > On 27 nov, 06:32, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >>>>> >> On Wed, 26 Nov 2008 17:09:40 -0800, bill.sloman wrote: >>>>> >> > On 26 nov, 22:17, Bill Ward <bw...(a)REMOVETHISix.netcom.com> >>>>> >> > wrote: >>>>> >> >> On Wed, 26 Nov 2008 07:53:11 -0800, bill.sloman wrote: >>>>> >> >> > On 26 nov, 12:28, Whata Fool <wh...(a)fool.ami> wrote: >>>>> >> >> >> Eeyore <rabbitsfriendsandrelati...(a)hotmail.com> wrote: >>>>> >>>>> >> >> >> >bill.slo...(a)ieee.org wrote: >>>>> >>>>> > <snip> >>>>> >>>>> >> As you put it up thread, "the stratosphere isn't functioning as an >>>>> >> insulator." >>>>> >>>>> >> If the stratosphere is transparent, and there is an excess of >>>>> >> convective capacity in the troposphere (driven by the lapse rate), >>>>> >> how can trace amounts of CO2 affect surface temperatures? If >>>>> >> convection is sufficient to get latent heat to the tropopause, >>>>> >> where it can radiate from cloud tops, etc, it has a clear shot at >>>>> >> 3K deep space. The tropopause is there because it represents the >>>>> >> top of the convective mixing layer. Because of increasing UV >>>>> >> heating, the stratosphere has an inverted lapse rate, which >>>>> >> prevents convection. >>>>> >>>>> > You seem to have set up a straw man by claiming that you can slice >>>>> > the atmosphere into three layers - >>>>> >>>>> > - the troposphere where heat transfer is only by convection >>>>> >>>>> > - a very thin tropopause which does all the radiation >>>>> >>>>> > - the stratosphere which does nothing >>>>> >>>>> > which - unsurprisingly - leads you to incorrectly conclude that CO2 >>>>> > cann't do anything. >>>>> >>>>> Where did I say the radiation all comes from a thin layer? You must >>>>> be misinterpreting the concept of effective radiating altitude. >>>> >>>> I very much doubt it. The proposition that the you think that all the >>>> radiation comes from a thin layar at the tropopause folows direcly from >>>> your claim that radiation doesn't play a significant role anywhere in >>>> the troposphere, which strikes me as implausible. >>> >>>Below the effective radiating layer (cloud tops) radiation is swamped by >>>convection, so CO2 can have little effect. Above the radiating layer, >>>there's not much CO2 left, and the 15u band is off peak, so it can have >>>little effect. In the radiating layer, CO2 is radiating to space like >>>everything else. Why do you think the radiating layer must be thin? I >>>said "layer", not "surface". >>>> >>>>> >> >> IR radiated from the surface would be quickly absorbed by WV, >>>>> >> >> clouds, CO2, and other GHGs, and at 500W/m^2 would be >>>>> >> >> overwhelmed by the 10's of kW/m^2 available from convection of >>>>> >> >> latent heat. >>>>> >>>>> >> > Clouds scatter infra-red radiation rather than absorbing it. as >>>>> >> > do the greenhouse gases, but that's enough to sustain a thermal >>>>> >> > gradient. >>>>> >>>>> >> Surely you're not proposing the lapse rate is sustained by outgoing >>>>> >> IR. All the sources I've seen say the troposphere is due to >>>>> >> convection, not radiation. Can you find one to the contrary. >>>>> >>>>> > Don't have to. Convection and transport as latent heat both decrease >>>>> > rapidly as you move up through the troposphere, and radiation >>>>> > progressively takes over, becoming responsible for 100% of the heat >>>>> > transfer by the time you get to the tropopause. This is clearly >>>>> > implied by what I wrote earlier (which is why I've not snipped it). >>>>> >>>>> So you don't really understand convection or radiation. If you did, >>>>> you might see that radiation could not generate a "thermal gradient". >>>>> Radiation tends to equalize temperatures, you know. >>>> >>>> Only when it is reabsorbed. Radiation from the flanks of pressure- >>>> broadened rotational lines isn't going to be reabsorbed higher up where >>>> the pressure broadening is less, and radiation from water vapour isn't >>>> going to be absorbed once you get up to height where almost all the >>>> waer vapour has frozen out - which seems to be about half way through >>>> the troposphere, if I've correctly interpreted the significance of the >>>> effective radiating altitude (which is an average over all >>>> wavelengths). >>> >>>So you really think the lapse rate is set by radiation? And it just >>>happens to be near adiabatic? Fascinating. >> >> No, does not happen to be near adiabatic, but near the lower one of 2 >> adiabatic rates - the wet one. > >Perhaps that's because the surface is not always warm enough to support >convection. Especially in dry air. > >> Radiation is not the main force affecting that, but has a major >> influence - especially where the local lapse rate is short of causing >> convection (a majority of the world). > >In reality, isn't the local lapse rate the result of cooling? If you >started with an equal temperature at all altitudes, you'd have an >inversion until the higher altitudes cooled enough or the surface warmed >enough to cause convection. Equal temperature at all altitudes is not an inversion. But generally the air well aloft cools and the surface warms, especially in the tropics - where the surface is warmed the most. In the ITCZ, rising air is cooled mainly by adiabatic expansion - often to a temperature so cold at the equatorial tropopause that radiation actually warms it. Elsewhere, air far aloft usually experiences cooling by radiation. At the poles, all altitudes tend to have net radiation effect being cooling. Outside the tropics, there is a lot of impairment of convection by advance of cold air in the lower troposphere and advance of warmer air in the upper troposphere and at altitudes which are troposphere in the tropics and stratosphere elsewhere. At the poles, the surface experiences cooling by radiation to get rid of heat brought in by ocean currents and air from elsewhere. >If you heat the surface and cool at high altitude, convection appears >inevitable, especially if the atmosphere is opaque to thermal IR. At the poles, air is warmed by adiabatic compression as it descends - and cools by radiation as it descends, or else it would warm at the dry adiabatic lapse rate. And the surface also cools by radiation. >>>Somehow I'm reminded of the adage,"When all you have is a hammer, >>>everything looks like a nail." >>> >>>http://en.wikipedia.org/wiki/Troposphere >>> >>>"The word troposphere derives from the Greek "tropos" for "turning" or >>>"mixing," reflecting the fact that turbulent mixing plays an important >>>role in the troposphere's structure and behavior." I checked that out - true. I usually see "weather sphere". >>>You think IR is doing the mixing? Only when it's converted to sensible >>>heat. >> >> A lot of the churning is advection rather than vertical convection. A >> significant part of the world even does not have much of either at any >> given moment. > >What would drive horizontal advection if not density differences and >resulting vertical convection? >> >> GHGs will increase the lapse rate where there is room for the lapse >> rate to increase. > >I don't quite understand what "room for the lapse rate to increase" means. >What limits it? Warm air advancing at higher levels Cool air advancing at lower levels Surface or low clouds being cooled rather than warmed by net radiation - such as at night or at the poles. >>>>> It's described by all that second law stuff you must have somehow >>>>> skipped over. >>>> >>>> If only I could have skipped over it. I had to slog my way through a >>>> lot of work to get my head around that concept back in 1961, but my >>>> subsequent encounters with the subject do suggest that my teachers >>>> managed to get me onto the right track. >>> >>>Just keep in mind you can't actually heat a hot source from a cold >>>target. All you can do is slow the rate of cooling of the hot source. >>>The sky is cold, the surface is hot. >> >> GHGs will slow the cooling by making outgoing radiation from the >> surface absorbed at a lower, warmer level, which radiates half its >> radiation downward. > >I prefer to think of the net radiation being reduced because the target >target temperature is not 0K. There is never any net radiation from cold >to hot. There is not - but the radiation from hot to cold can be impeded by adding absorptions and re-emissions along the way. Half the re-emissions at any given layer in between are in the direction of cold to hot, forcing the hot side to get hotter than otherwise to accomplish the same amount of radiative heat transfer. >>>>> The lapse rate is set by gas laws. Convection occurs because warm >>>>> air is less dense than cold air, so it rises, expands, and >>>>> adiabatically cools, still maintaining a higher temperature than its >>>>> surroundings. It continues up until it reaches an altitude where the >>>>> air around it is slightly warmer (the lapse rate changes) than its >>>>> adiabatic temperature, where it releases its excess energy and stops, >>>>> moving the lapse rate toward adiabatic. >>>>> >>>>> If the air rises to its dewpoint temperature, WV condenses, releasing >>>>> latent heat and giving the rising parcel a boost. Go out and watch a >>>>> cumulus cloud and you can see the flat bottom at the condensation >>>>> altitude, and the energetic billowing of the cloud upward from the >>>>> latent heat release. The principle is scalable, that's why >>>>> thunderstorms can billow up well into the stratosphere, yielding the >>>>> "anvil" shape. >>>> >>>> Thunderheads are rare. Normally all the water vapour (and the latent >>>> heat) has condensed out at around 6km, and that - large - proportion >>>> of the greenhouse effect that depends on absorption by lines in the >>>> water vapour spectrum goes away, and - for those wavelengths - this >>>> opens the window to outer space. >>> >>>Check out a satellite view of the tropics. Deep convection is pretty >>>common. >> >> It is common there, though in quite a minority of the tropics. > >It doesn't have to be everywhere. It does indeed set the lapse rate in much of the tropics in the daytime. At night, the lapse rate in the lowest several hundred meters is less. Elsewhere where the surface is cooler and the 120 millibar level is not will have plenty of areas where the lapse rate is short of adiabatic. >>>>> >> > Convection becomes progressively less potent as air pressure and >>>>> >> > thus density declines with height, and as the partial pressure >>>>> >> > of water vapour declines with decreasing temperature as it >>>>> >> > climbs up through the tropopause, so the amount of energy >>>>> >> > transferred as latent heat falls away with height in the same >>>>> >> > sort of way. >>>>> >>>>> See above, then consider what happens when an airplane encounters a >>>>> TS at 20000 feet. IR doesn't disassemble aircraft in flight. There's >>>>> plenty of energy in convection, even at altitude. >>>> >>>> Thunderstorms don't occupy a particulary significant proportion of the >>>> sky. If you want to calculate the additional global warming you get >>>> from a few more parts per million of CO2, you don't need to allocate >>>> all that many cells to air columns that look like thunderheads. >>> >>>The point is that convection remains active, including destructive >>>turbulence, well into the stratosphere. The amount of energy cannot >>>decrease with increasing altitude. >> >> As long as local lapse rate does not fall below the relevant adiabatic >> one (the wet one at altitudes occupied by a thunderhead). >> >>> There's no way down. You can't transfer net energy from cold high >>>altitudes to the hot surface. >> >> You can slow down the upward transfer by radiation by adding more >> stops in the radiative path, by adding GHGs. > >EM travels at c. IR can be converted to sensible heat, but it can't be >slowed. Suppose the surface is at 288 K and radiating to some target layer at 225 K. Surface is radiating 39 mW/cm^2 and receiving 14.5 mW/cm^2. Net radiative heat transfer is 24.5 mW/cm^2. Now, add some layer in between that absorbs and reradiates everything. That intermediate layer then has to be at 288 K to transfer 24.5 mW/cm^2 to the top layer - and is as a net receiving 24.5 mW/cm^2 from the surface. That intermediate layer is radiating 39 mW/cm^2 to the surface, so the surface has to be radiating 63.5 mW/cm^2 in order to achieve net upward radiative heat transfer of 24.5 mW/cm^2. A blackbody needs to be at 325 K to transfer 24.5 mW/cm^2 to the 225 K outer layer with an absorbing/reradiating layer in between. >> <SNIP> >> >>>>> Second, apparently you think a model is only useful if it, "(gives) >>>>> the right sort of answer". Yet you continue to prattle on about >>>>> radiative transfer models even though you admit they would only be >>>>> useful in a limited region at the top of the troposphere. >>>> >>>> Since the effective radiating altitude is 6km above ground, right in >>>> the middle of the troposphere, this seems to be exactly the right >>>> place for a radiative transfer model to be effective. >> >> I think it's higher - though I am catching an error in my calculation >> that it is at the 300 mb level. I now calculate that it's the 350 mb >> level, around 8 km. > >Is it at 255K? That seems to be the usual figure. I was figuring lower - Earth is receiving solar radiation at a rate per unit surface area of about 1/8 the solar constant. Cross section is pi times radius squared, surface area is 4 times that, and albedo is about 50%. Blackbody radiates 1/8 of 1366 watts/m^2 at about 234 K. If low temperature emissivity of Earth as a whole is the .95 that instructional material for my non-contact thermometer says is close enough to ("my words") "1-size-fits-all" for nonmetallic materials, make that "effective radiating temperature" 237 K. >>>There's an excess of water vapor available to convect latent heat up to >>>the effective radiating altitude. >> >> Except most of the world lacks convection, and my non-contact >> thermometer usually gets a much colder reading for the sky than it gets >> from the ground. > >It's only important where cooling is happening. There's no reason to >believe it has to be the same all over the globe. > >>> It's in the 10s of kW/m^2 compared to >>>the 500W/m^2 max from surface radiation. The lower troposphere is >>>translucent in the 15u band. How could CO2 play any significant part, >>>compared to radiation? >> >> More CO2 means the lower troposphere gets more opaque in the 15 um >> band. > >Which makes convection more effective by converting IR to hot air. Or which makes the surface or lower atmosphere warmer than otherwise when those can warm up by some amount without achieving convection. That's most of the world at night and a fair amount of daylit area outside the tropics. >>> Above the clouds, it has a clear shot to space. >> >> What about where the tops of the highest clouds are below the 700 mb >> level? What about in the clear half of the world? > >It doesn't have to be everywhere to be an effective mechanism. It has a significant effect, but significant radiation comes from clear air and from ground. The ground does cool easily at night when there are no clouds overhead and when there is no convection. >>>> In fact it looks to me as if we need to regard the effective radiating >>>> altitude as wavelength dependent. This altitude (when averaged over >>>> all wavelengths) seems to coincide with the 6km where you'd expect >>>> water vapour to stop being an an effective greenhouse gas (because it >>>> is frozen out at higher altitudes). For the limited number of >>>> wavelengths where carbon dioxide absorbs the effective radiating >>>> altitude seems likely to be up in the stratosphere, where the air is a >>>> lot colder (below the very low density outer bit which gets heated by >>>> charged particles from the sun). >>> >>>And where the CO2 has a cooling effect. The stratosphere has an >>>inverted lapse rate. >> >> The upper stratosphere has lower ability to radiate IR than lower >> levels of the atmosphere and bears the brunt of absorption of UV around >> 150-210 nm or somthing like that. That's why the upper half (or 2/3 or >> whatever) of the stratosphere has an inverted lapse rate. > >Which means it should be hotter and radiate more. It's hotter, but radiates less easily than the more-GHG-dense atmosphere underneath. It is indeed cooled by radiation. This is mainly above the altitude of the equatorial tropopause - which is around the 110-120 mb level, above 88-89% of GHGs other than water vapor and above a much higher percentage of water vapor. Between the stratosphere and the thermosphere is the mesosphere, with lapse rate in the direction of getting colder with increasing altitude. Apparently GHG radiating ability decreases less than absorption of solar UV does as altitude increases through that layer, though both figures are very low. >> CO2's 15 um band plays a significant role from the lower stratosphere >> through the lower troposphere. > >I'm still not convinced of that. A blackbody radiator at relevant temperatures (220-320 K) has radiation at least 60% of that of peak wavelength at 15 um. - Don Klipstein (don(a)misty.com)
From: Don Klipstein on 20 Dec 2008 00:01 In article <pan.2008.12.09.00.55.04.957689(a)REMOVETHISix.netcom.com>, Bill Ward wrote: >On Mon, 08 Dec 2008 07:15:34 -0800, bill.sloman wrote: > >> On 8 dec, 05:42, d...(a)manx.misty.com (Don Klipstein) wrote: >>> In article <tqb3j4pmpsqj32hes94kb9pni1vaup6...(a)4ax.com>, Whata Fool >>> wrote: >>> >bill.slo...(a)ieee.org wrote: >>> >>> >>On 28 nov, 21:43, Whata Fool <wh...(a)fool.ami> wrote: >>> >>> bill.slo...(a)ieee.org wrote: >>> >>> >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: >>> >>> <I snip to edit for space> >>> >>> >>> >> >You've misunderstood. The surface of the earth is ultimately >>> >>> >> >cooled by radiation to outer space, but the "surface" that is >>> >>> >> >cooled depends on the frequency that is being radiated. >>> >>> >>> >> The frequency is determined by temperature, isn't it? >>> >>> >>> >A black-body radiator emits a wide range of frequencies. The centre >>> >>> >of the range does move to higher frequencies as the temperature of >>> >>> >the emitter gets higher, but it doesn't move all that fast. >>> >>> >>> Broadband radiation may resemble black body, but CO2 does >>> >>> not radiate broadband. >>> >>> >>True, But it continues to emit at all the frequencies it can over a >>> >>range of temperatures; >>> >>> > The CO2 spectra is mostly narrow spikes, and supposedly >>> >those spikes are pretty much fixed to a certain range of temperatures, >>> >show any reference that suggests otherwise. >>> >>> The 15 um band of CO2 looks fairly broad here, comparable to the 2 >>> broader water vapor bands at 6 and 2.5 um: >>> >>> http://www.iitap.iastate.edu/gccourse/forcing/images/image7.gif >> >> This spectrum covers a wide range of wavelengths, and doesn't ressolve the >> rotational fine structure. >> I've not had much luck finding spectra that do show the fine structure. >> >> The best I've been able to do is here >> >> http://www.anl.gov/PCS/acsfuel/preprint%20archive/Files/35_3_WASHINGTON%20DC_08-90_0738.pdf >> >> and since the pdf was generated by scanning a printed document, the >> figures at the end of the document are none too clear. >>> >>> > Actually, water vapor is almost BB at certain temperatures, >>> >that can't be said for CO2. >>> >>> Water vapor has significant gaps. >>> >>> Same source: >>> http://www.iitap.iastate.edu/gccourse/forcing/images/image7.gif >>> >>> >>as it gets colder the number of phtotons emitted at shorter wavelegths >>> >>goes down faster than the number emitted at longer wavelengths, which >>> >>implies something rather from your "the frequency is determined by >>> >>temperature". >>> >>> > Exactly, so the net energy transfer is a function of relative >>> >temperature differences, say it anyway you want, but 388 parts per >>> >million is a very small amount. >> >> But quite enough to repeatedly absorb and re-emit all the radiation at the >> CO2 wavelengths as it goes through the atmosphere. > >Now what happens to the IR when it's absorbed? It goes to heat. Heat >convects. Not where the local lapse rate is well below the relevant adiabatic one. The temperature will get warmer than otherwise instead. > That "re-radiation" bit is bogus. The gas is the same as any >other, just warmer, and maintaining radiative equilibrium. I'm surprised >you fell for that pinball explanation of radiative transport. IR travels >at c. When it's converted to heat, it warms the gas, and allows >convection to take place as soon as the lapse rate allows. If a layer opaque to longwave IR is added between the surface and what the surface radiates to, then that new layer's temperature will be the previous surface temperature. The surface will have to get warmer still in order to transfer heat (from solar radiation) to that layer. Adding GHGs effectively does that to some extent. Consider that most of the surface can get significantly warmer than it is now before such a temperature rise initiates convection. - Don Klipstein (don(a)misty.com)
From: Bill Ward on 20 Dec 2008 01:41
On Sat, 20 Dec 2008 04:52:58 +0000, Don Klipstein wrote: > In article <pan.2008.12.08.09.21.16.182224(a)REMOVETHISix.netcom.com>, Bill > Ward wrote: >>On Mon, 08 Dec 2008 04:30:44 +0000, Don Klipstein wrote: >> >>> In article <pan.2008.11.29.05.43.32.198332(a)REMOVETHISix.netcom.com>, >>> Bill Ward wrote in part: >>>>On Fri, 28 Nov 2008 19:25:22 -0800, bill.sloman wrote: >>>> >>>>> On 27 nov, 20:50, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >>>>>> On Thu, 27 Nov 2008 07:50:47 -0800, bill.sloman wrote: >>>>>> > On 27 nov, 06:32, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >>>>>> >> On Wed, 26 Nov 2008 17:09:40 -0800, bill.sloman wrote: >>>>>> >> > On 26 nov, 22:17, Bill Ward <bw...(a)REMOVETHISix.netcom.com> >>>>>> >> > wrote: >>>>>> >> >> On Wed, 26 Nov 2008 07:53:11 -0800, bill.sloman wrote: >>>>>> >> >> > On 26 nov, 12:28, Whata Fool <wh...(a)fool.ami> wrote: >>>>>> >> >> >> Eeyore <rabbitsfriendsandrelati...(a)hotmail.com> wrote: >>>>>> >>>>>> >> >> >> >bill.slo...(a)ieee.org wrote: >>>>>> >>>>>> > <snip> >>>>>> >>>>>> >> As you put it up thread, "the stratosphere isn't functioning as >>>>>> >> an insulator." >>>>>> >>>>>> >> If the stratosphere is transparent, and there is an excess of >>>>>> >> convective capacity in the troposphere (driven by the lapse >>>>>> >> rate), how can trace amounts of CO2 affect surface temperatures? >>>>>> >> If convection is sufficient to get latent heat to the tropopause, >>>>>> >> where it can radiate from cloud tops, etc, it has a clear shot at >>>>>> >> 3K deep space. The tropopause is there because it represents the >>>>>> >> top of the convective mixing layer. Because of increasing UV >>>>>> >> heating, the stratosphere has an inverted lapse rate, which >>>>>> >> prevents convection. >>>>>> >>>>>> > You seem to have set up a straw man by claiming that you can slice >>>>>> > the atmosphere into three layers - >>>>>> >>>>>> > - the troposphere where heat transfer is only by convection >>>>>> >>>>>> > - a very thin tropopause which does all the radiation >>>>>> >>>>>> > - the stratosphere which does nothing >>>>>> >>>>>> > which - unsurprisingly - leads you to incorrectly conclude that >>>>>> > CO2 cann't do anything. >>>>>> >>>>>> Where did I say the radiation all comes from a thin layer? You must >>>>>> be misinterpreting the concept of effective radiating altitude. >>>>> >>>>> I very much doubt it. The proposition that the you think that all the >>>>> radiation comes from a thin layar at the tropopause folows direcly >>>>> from your claim that radiation doesn't play a significant role >>>>> anywhere in the troposphere, which strikes me as implausible. >>>> >>>>Below the effective radiating layer (cloud tops) radiation is swamped >>>>by convection, so CO2 can have little effect. Above the radiating >>>>layer, there's not much CO2 left, and the 15u band is off peak, so it >>>>can have little effect. In the radiating layer, CO2 is radiating to >>>>space like everything else. Why do you think the radiating layer must >>>>be thin? I said "layer", not "surface". >>>>> >>>>>> >> >> IR radiated from the surface would be quickly absorbed by WV, >>>>>> >> >> clouds, CO2, and other GHGs, and at 500W/m^2 would be >>>>>> >> >> overwhelmed by the 10's of kW/m^2 available from convection of >>>>>> >> >> latent heat. >>>>>> >>>>>> >> > Clouds scatter infra-red radiation rather than absorbing it. as >>>>>> >> > do the greenhouse gases, but that's enough to sustain a thermal >>>>>> >> > gradient. >>>>>> >>>>>> >> Surely you're not proposing the lapse rate is sustained by >>>>>> >> outgoing IR. All the sources I've seen say the troposphere is due >>>>>> >> to convection, not radiation. Can you find one to the contrary. >>>>>> >>>>>> > Don't have to. Convection and transport as latent heat both >>>>>> > decrease rapidly as you move up through the troposphere, and >>>>>> > radiation progressively takes over, becoming responsible for 100% >>>>>> > of the heat transfer by the time you get to the tropopause. This >>>>>> > is clearly implied by what I wrote earlier (which is why I've not >>>>>> > snipped it). >>>>>> >>>>>> So you don't really understand convection or radiation. If you did, >>>>>> you might see that radiation could not generate a "thermal >>>>>> gradient". Radiation tends to equalize temperatures, you know. >>>>> >>>>> Only when it is reabsorbed. Radiation from the flanks of pressure- >>>>> broadened rotational lines isn't going to be reabsorbed higher up >>>>> where the pressure broadening is less, and radiation from water >>>>> vapour isn't going to be absorbed once you get up to height where >>>>> almost all the waer vapour has frozen out - which seems to be about >>>>> half way through the troposphere, if I've correctly interpreted the >>>>> significance of the effective radiating altitude (which is an average >>>>> over all wavelengths). >>>> >>>>So you really think the lapse rate is set by radiation? And it just >>>>happens to be near adiabatic? Fascinating. >>> >>> No, does not happen to be near adiabatic, but near the lower one of 2 >>> adiabatic rates - the wet one. >> >>Perhaps that's because the surface is not always warm enough to support >>convection. Especially in dry air. >> >>> Radiation is not the main force affecting that, but has a major >>> influence - especially where the local lapse rate is short of causing >>> convection (a majority of the world). >> >>In reality, isn't the local lapse rate the result of cooling? If you >>started with an equal temperature at all altitudes, you'd have an >>inversion until the higher altitudes cooled enough or the surface warmed >>enough to cause convection. > > Equal temperature at all altitudes is not an inversion. But generally > the air well aloft cools and the surface warms, especially in the tropics > - where the surface is warmed the most. > > In the ITCZ, rising air is cooled mainly by adiabatic expansion - often > to a temperature so cold at the equatorial tropopause that radiation > actually warms it. Elsewhere, air far aloft usually experiences cooling > by radiation. At the poles, all altitudes tend to have net radiation > effect being cooling. > > Outside the tropics, there is a lot of impairment of convection by > advance of cold air in the lower troposphere and advance of warmer air in > the upper troposphere and at altitudes which are troposphere in the > tropics and stratosphere elsewhere. At the poles, the surface experiences > cooling by radiation to get rid of heat brought in by ocean currents and > air from elsewhere. > >>If you heat the surface and cool at high altitude, convection appears >>inevitable, especially if the atmosphere is opaque to thermal IR. > > At the poles, air is warmed by adiabatic compression as it descends - > and cools by radiation as it descends, or else it would warm at the dry > adiabatic lapse rate. And the surface also cools by radiation. > >>>>Somehow I'm reminded of the adage,"When all you have is a hammer, >>>>everything looks like a nail." >>>> >>>>http://en.wikipedia.org/wiki/Troposphere >>>> >>>>"The word troposphere derives from the Greek "tropos" for "turning" or >>>>"mixing," reflecting the fact that turbulent mixing plays an important >>>>role in the troposphere's structure and behavior." > > I checked that out - true. I usually see "weather sphere". > >>>>You think IR is doing the mixing? Only when it's converted to sensible >>>>heat. >>> >>> A lot of the churning is advection rather than vertical convection. >>> A >>> significant part of the world even does not have much of either at any >>> given moment. >> >>What would drive horizontal advection if not density differences and >>resulting vertical convection? >>> >>> GHGs will increase the lapse rate where there is room for the lapse >>> rate to increase. >> >>I don't quite understand what "room for the lapse rate to increase" >>means. What limits it? > > Warm air advancing at higher levels > Cool air advancing at lower levels > Surface or low clouds being cooled rather than warmed by net radiation - > such as at night or at the poles. > >>>>>> It's described by all that second law stuff you must have somehow >>>>>> skipped over. >>>>> >>>>> If only I could have skipped over it. I had to slog my way through a >>>>> lot of work to get my head around that concept back in 1961, but my >>>>> subsequent encounters with the subject do suggest that my teachers >>>>> managed to get me onto the right track. >>>> >>>>Just keep in mind you can't actually heat a hot source from a cold >>>>target. All you can do is slow the rate of cooling of the hot source. >>>>The sky is cold, the surface is hot. >>> >>> GHGs will slow the cooling by making outgoing radiation from the >>> surface absorbed at a lower, warmer level, which radiates half its >>> radiation downward. >> >>I prefer to think of the net radiation being reduced because the target >>target temperature is not 0K. There is never any net radiation from cold >>to hot. > > There is not - but the radiation from hot to cold can be impeded by > adding absorptions and re-emissions along the way. Half the re-emissions > at any given layer in between are in the direction of cold to hot, forcing > the hot side to get hotter than otherwise to accomplish the same amount of > radiative heat transfer. > >>>>>> The lapse rate is set by gas laws. Convection occurs because warm >>>>>> air is less dense than cold air, so it rises, expands, and >>>>>> adiabatically cools, still maintaining a higher temperature than its >>>>>> surroundings. It continues up until it reaches an altitude where the >>>>>> air around it is slightly warmer (the lapse rate changes) than its >>>>>> adiabatic temperature, where it releases its excess energy and >>>>>> stops, moving the lapse rate toward adiabatic. >>>>>> >>>>>> If the air rises to its dewpoint temperature, WV condenses, >>>>>> releasing latent heat and giving the rising parcel a boost. Go out >>>>>> and watch a cumulus cloud and you can see the flat bottom at the >>>>>> condensation altitude, and the energetic billowing of the cloud >>>>>> upward from the latent heat release. The principle is scalable, >>>>>> that's why thunderstorms can billow up well into the stratosphere, >>>>>> yielding the "anvil" shape. >>>>> >>>>> Thunderheads are rare. Normally all the water vapour (and the latent >>>>> heat) has condensed out at around 6km, and that - large - proportion >>>>> of the greenhouse effect that depends on absorption by lines in the >>>>> water vapour spectrum goes away, and - for those wavelengths - this >>>>> opens the window to outer space. >>>> >>>>Check out a satellite view of the tropics. Deep convection is pretty >>>>common. >>> >>> It is common there, though in quite a minority of the tropics. >> >>It doesn't have to be everywhere. > > It does indeed set the lapse rate in much of the tropics in the daytime. > At night, the lapse rate in the lowest several hundred meters is less. > > Elsewhere where the surface is cooler and the 120 millibar level is not > will have plenty of areas where the lapse rate is short of adiabatic. > >>>>>> >> > Convection becomes progressively less potent as air pressure >>>>>> >> > and thus density declines with height, and as the partial >>>>>> >> > pressure of water vapour declines with decreasing temperature >>>>>> >> > as it climbs up through the tropopause, so the amount of energy >>>>>> >> > transferred as latent heat falls away with height in the same >>>>>> >> > sort of way. >>>>>> >>>>>> See above, then consider what happens when an airplane encounters a >>>>>> TS at 20000 feet. IR doesn't disassemble aircraft in flight. >>>>>> There's plenty of energy in convection, even at altitude. >>>>> >>>>> Thunderstorms don't occupy a particulary significant proportion of >>>>> the sky. If you want to calculate the additional global warming you >>>>> get from a few more parts per million of CO2, you don't need to >>>>> allocate all that many cells to air columns that look like >>>>> thunderheads. >>>> >>>>The point is that convection remains active, including destructive >>>>turbulence, well into the stratosphere. The amount of energy cannot >>>>decrease with increasing altitude. >>> >>> As long as local lapse rate does not fall below the relevant >>> adiabatic >>> one (the wet one at altitudes occupied by a thunderhead). >>> >>>> There's no way down. You can't transfer net energy from cold high >>>>altitudes to the hot surface. >>> >>> You can slow down the upward transfer by radiation by adding more >>> stops in the radiative path, by adding GHGs. >> >>EM travels at c. IR can be converted to sensible heat, but it can't be >>slowed. > > Suppose the surface is at 288 K and radiating to some target layer at > 225 K. > > Surface is radiating 39 mW/cm^2 and receiving 14.5 mW/cm^2. Net > radiative heat transfer is 24.5 mW/cm^2. > > Now, add some layer in between that absorbs and reradiates everything. > > That intermediate layer then has to be at 288 K to transfer 24.5 mW/cm^2 > to the top layer - and is as a net receiving 24.5 mW/cm^2 from the > surface. > > That intermediate layer is radiating 39 mW/cm^2 to the surface, so the > surface has to be radiating 63.5 mW/cm^2 in order to achieve net upward > radiative heat transfer of 24.5 mW/cm^2. A blackbody needs to be at 325 > K to transfer 24.5 mW/cm^2 to the 225 K outer layer with an > absorbing/reradiating layer in between. That seems to assume the active layers are somehow fixed in place. If they are gases, they will warm as they absorb IR, become less dense and convect. Another way to look at it is to assume the optically dense gas layer is simply heated by surface IR, maintaining radiative equilibrium with the surface at the lower skin, then moves the heat through the layer by conduction and convection to the top skin, which is in turn in radiative equilibrium with the upper target. I see no reason to assume that IR is carrying heat through an optically dense gas. Conduction and convection seem to work quite adequately in humid air except when the climate somehow becomes involved. How does the gas know whether it should be internally carrying heat by conduction or radiation? Isn't the result the same? It seems much less complicated to assume the layers are simply hot gas, and will transfer heat internally just as gases do in all other disciplines, with radiative transfer only as needed through any radiatively inactive regions (which will still convect and conduct). Heat will eventually tend to rise through the troposphere, whether by radiation or convection. If IR is absorbed in the gas, the resulting hot spot will rise via density differences. I don't see any other choice. All gases have thermal conductivity, independent of radiative transfer. > >>> <SNIP> >>> >>>>>> Second, apparently you think a model is only useful if it, "(gives) >>>>>> the right sort of answer". Yet you continue to prattle on about >>>>>> radiative transfer models even though you admit they would only be >>>>>> useful in a limited region at the top of the troposphere. >>>>> >>>>> Since the effective radiating altitude is 6km above ground, right in >>>>> the middle of the troposphere, this seems to be exactly the right >>>>> place for a radiative transfer model to be effective. >>> >>> I think it's higher - though I am catching an error in my >>> calculation >>> that it is at the 300 mb level. I now calculate that it's the 350 mb >>> level, around 8 km. >> >>Is it at 255K? That seems to be the usual figure. > > I was figuring lower - Earth is receiving solar radiation at a rate > per > unit surface area of about 1/8 the solar constant. Cross section is pi > times radius squared, surface area is 4 times that, and albedo is about > 50%. Blackbody radiates 1/8 of 1366 watts/m^2 at about 234 K. > If low temperature emissivity of Earth as a whole is the .95 that > instructional material for my non-contact thermometer says is close > enough to ("my words") "1-size-fits-all" for nonmetallic materials, make > that "effective radiating temperature" 237 K. Those are probably different initial assumptions than the other calculation used. >>>>There's an excess of water vapor available to convect latent heat up >>>>to the effective radiating altitude. >>> >>> Except most of the world lacks convection, and my non-contact >>> thermometer usually gets a much colder reading for the sky than it >>> gets from the ground. >> >>It's only important where cooling is happening. There's no reason to >>believe it has to be the same all over the globe. >> >>>> It's in the 10s of kW/m^2 compared to >>>>the 500W/m^2 max from surface radiation. The lower troposphere is >>>>translucent in the 15u band. How could CO2 play any significant part, >>>>compared to radiation? >>> >>> More CO2 means the lower troposphere gets more opaque in the 15 um >>> band. >> >>Which makes convection more effective by converting IR to hot air. > > Or which makes the surface or lower atmosphere warmer than otherwise > when those can warm up by some amount without achieving convection. > That's most of the world at night and a fair amount of daylit area > outside the tropics. Yes. Places where there's relatively less cooling taking place. > >>>> Above the clouds, it has a clear shot to space. >>> >>> What about where the tops of the highest clouds are below the 700 mb >>> level? What about in the clear half of the world? >> >>It doesn't have to be everywhere to be an effective mechanism. > > It has a significant effect, but significant radiation comes from > clear > air and from ground. The ground does cool easily at night when there > are no clouds overhead and when there is no convection. But the surface is colder, so the T^4 factor kicks in. >>>>> In fact it looks to me as if we need to regard the effective >>>>> radiating altitude as wavelength dependent. This altitude (when >>>>> averaged over all wavelengths) seems to coincide with the 6km where >>>>> you'd expect water vapour to stop being an an effective greenhouse >>>>> gas (because it is frozen out at higher altitudes). For the limited >>>>> number of wavelengths where carbon dioxide absorbs the effective >>>>> radiating altitude seems likely to be up in the stratosphere, where >>>>> the air is a lot colder (below the very low density outer bit which >>>>> gets heated by charged particles from the sun). >>>> >>>>And where the CO2 has a cooling effect. The stratosphere has an >>>>inverted lapse rate. >>> >>> The upper stratosphere has lower ability to radiate IR than lower >>> levels of the atmosphere and bears the brunt of absorption of UV >>> around 150-210 nm or somthing like that. That's why the upper half >>> (or 2/3 or whatever) of the stratosphere has an inverted lapse rate. >> >>Which means it should be hotter and radiate more. > > It's hotter, but radiates less easily than the more-GHG-dense > atmosphere > underneath. It is indeed cooled by radiation. This is mainly above the > altitude of the equatorial tropopause - which is around the 110-120 mb > level, above 88-89% of GHGs other than water vapor and above a much > higher percentage of water vapor. > > Between the stratosphere and the thermosphere is the mesosphere, with > lapse rate in the direction of getting colder with increasing altitude. > Apparently GHG radiating ability decreases less than absorption of solar > UV does as altitude increases through that layer, though both figures > are very low. > >>> CO2's 15 um band plays a significant role from the lower >>> stratosphere >>> through the lower troposphere. >> >>I'm still not convinced of that. > > A blackbody radiator at relevant temperatures (220-320 K) has > radiation at least 60% of that of peak wavelength at 15 um. And CO2 is not a blackbody radiator. Looking at the wiki graph link, I'd guess that the 15u band could absorb only about 25% of the 310K blackbody radiation, and less, if Sloman was correct about the fine band structure leaving holes. |