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From: Don Klipstein on 7 Dec 2008 22:35 In article <pan.2008.11.27.19.50.55.98497(a)REMOVETHISix.netcom.com>, Bill Ward 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 trophosphere 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 can do >> anything. > >Where did I say the radiation all comes from a thin layer? You must be >misinterpreting the concept of effective radiating altitude. > >> >>> >> 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. It's described by >all that second law stuff you must have somehow skipped over. Radiation alone can generate a thermal gradient. Suppose the atmosphere completely lacked convexction and advection, was transparent to solar radiation but had GHGs. Solar radiation comes in and heats the surface. The surface radiates longer wavelength radiation. The longer wavelength radiation from the surface gets absorbed and re-radiated many times before it gets out of the atmosphere. There needs to be a temperature gradient in order to achieve heat transport, even in such a "radiation layer". The Sun actually has such a layer outside the core where heat transport is by radiation absorbed and re-radiated many times, rather than by convection. There is a temperature gradient in order for heat transport to be upward. Any given parcel of gas radiates a little more upward than it receives from above, and receives a little more from below than it radiates downward. >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. Except most of the atmosphere has lapse rate less than adiabatic due to: 1. Radiational cooling of the surface (some radiation from the surface gets pretty far - ever read the sky with a non contact thermometer?). 2. Many areas have lower atmospheric air coming from somewhere else cooler and/or upper atmospheric air coming from someplace else warmer. >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. The top of the anvil is the tropopause. Also, most cumulus clouds don't become thunderstorms but stop growing with their tops in the lower half of the troposphere. There are also plenty of clouds other than cumulus, much of them formed by air rising gradually while moving mainly horizontally. Sometimes the lapse rate is a close match to the adiabatic lapse rate (the dry one at altitudes lacking clouds, and the wet one at altitudes having them). More often it is less. >>> > 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. Yes, there are little spots where vertical convection causes considerable release of energy. Most heat transfer throughout the atmosphere is otherwise - advection and radiation, especially advection. >Now why did you try to hide what I was responding to? You should know >that won't work. > ><unsnip> > >>> At night, convection stops, but cooling is not required at night. >>> Convection kicks in during the day, when cooling is needed. >>> >>> I don't see how radiative cooling is even necessary below the cloud >>> tops, since there's plenty of cooling capacity from convection. >> >> And there's solar energy availalbe to fuel it. > ><end unsnip> >> >>> Exactly. It's a heat engine, with water as the working fluid. It cools >>> the surface by using solar energy to convect latent heat to the cloud >>> tops, from which it radiates as a black body to deep space. Cloud >>> shadows are a strong, easily observable negative temperature feedback, >>> since they cut off surface heating as the clouds develop. >>> >>> >> Once the energy reaches the tropopause, as you imply, it's a pretty >>> >> straight shot to 3K deep space, since there's not much atmosphere >>> >> left to absorb IR. >> >> 25% of the mass of the atmosphere lies above the tropopause, and 25% of >> the CO2. There's very little water vapour in the stratosphere - at -55C >> any water around is ice. > >You need to keep your stories straight: > >Up thread, on: Wed, 26 Nov 2008 07:53:11 -0800 (PST) > >You said: >"Sure. Most of the mass of the atmosphere - about 90% - is below the >tropopause. But the stratosphere stretches out quite a long way." > >Do you always adjust the facts to match your argument? >How do you expect to retain any credibility? Looks like he did do a bit of research or learning on that matter recently - although in parts of the world (the tropics) the tropopause is indeed over almost 90% of the atmosphere. Elsewhere the tropopause is lower. In the "middle latitudes" the tropopause is indeed close to the 250 mb level on average, though varying. Water vapor is mostly in the troposphere whether the stratosphere has 10% or 25% of the mass of the atmosphere. CO2 in the stratosphere counts for something, especially in the areas of the world where the tropopause is lower. >>> >> Perhaps it's easier to see if you look at the lapse rate as bounded >>> >> at the top by the effective radiating temperature, and consider the >>> >> surface temperatures as derived from that and the adiabatic lapse >>> >> rate. >>> >>> > This approach doesn't make it easy to see how increasing levels of >>> > greenhouse gases produce more greenhouse warming. >>> >>> Correct. Now show me how greenhouse warming is supposed to work, in >>> view of the inconsistencies I've pointed out. >> >> This was a pedagogic point. I didn't intend to suggest that CO2 wasn't >> an effective greenhouse gas, merely that this wasn't a way of looking at >> what was going on that was helpful in letting you see where the >> greenhouse effect is going on. > >So where is your explanation of how greenhouse warming is supposed to >work, in view of the inconsistencies I've pointed out? > >>> CO2 isn't effective in the troposphere, because radiation is swamped by >>> the convective transfer required to maintain the lapse rate. CO2 >>> isn't effective in the stratosphere, partly because there's so little >>> left, and partly because it would actually cool by radiating IR at the >>> higher stratospheric temperatures. >>> >>> So where is the CO2 causing global warming? >> >> CO2 is not effective at the bottom of the troposphere, but it becomes >> progressively more effective as you climb up through the troposphere >> towards the tropopause. >> and presumably exerts most of its effect in the upper layers of the >> troposphere, where - incidentally - there isn't much water vapour left, >> since it freezes out as the air gets higher and colder. >> >>> > Convective heat >>> > transfer normally stops at the tropopause - though energetic thunder- >>> > heads can go higher for a while - and slows down a lot before it gets >>> > to the tropopause, so presumably the greenhouse effect is mainly >>> > active in the upper layers of the troposphere. >>> >>> Which is above most of the atmosphere, and dry, so the postulated >>> positive feedback from WV also looks highly unlikely. >> >> Only if you persist in thinking that everything has to happen in an >> infinitely thin layer, which isn't a realistic model (which might not >> matter if it gave the right sort of answer, which it doesn't), nor - >> more important - a useful model, > >First, the thin layer bit is yours - I never even implied it. > >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. Or anywhere that the lapse rate is short of adiabatic. There are plenty of times I have no convection from the ground to air higher up, and my non-contact thermometer gets a much lower reading for the sky than it does for the ground. >>> I'm slightly encouraged by your post. Did I misinterpret any of the >>> points where you appear to agree with me? >> >> Obviously. > >Well, optimism loses again. - Don Klipstein (don(a)misty.com)
From: Don Klipstein on 7 Dec 2008 22:54 In <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: >>> >>> > <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. What about in the majority of the troposphere lacking convection? And how are cloud tops the effective radiating layer in the half of the world that lacks clouds? > Above the radiating layer, there's not much CO2 left, Assuming Earth reflects half of solar radiation and has .95 emissivity of low temperature thermal IR (the figure on my non contact thermometer), Earth radiation achieve radiation balance at 237-238 K. (I may have posted a few degrees lower before by forgetting the .95 figure). 237 K is about -36 C. 237 K is when 95% of blackbody radiation intensity is 1/8 of the solar constant. Average location of a photon radiated from Earth to outer space is where temp. is -36 C, but that is give-or-take a lot, since a lot of thermal radiation can go some fair distance through the atmosphere before being absorbed. On average, the altitude at which temperature is 237 K is around the 300 mb level, which has about 30% of the mass of the atmosphere above it. However, a lot of photons radiated to space from Earth come from greatly different altitudes, some of which have more than 30% of the atmosphere overhead. > and the 15u band is off peak, Peak wavelength of a blackbody at 237 K is around 12.5 um. At 15 um, radiation is about 91% of that at peak wavelength. <Snip from here - will respond to other points in a separate post> - Don Klipstein (don(a)misty.com)
From: Don Klipstein on 7 Dec 2008 23:30 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. 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). >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." > >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. GHGs will increase the lapse rate where there is room for the lapse rate to increase. >>> 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. >>> 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. >>> >> > 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. <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. >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 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. > 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? >> 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. CO2's 15 um band plays a significant role from the lower stratosphere through the lower troposphere. - Don Klipstein (don(a)misty.com)
From: Don Klipstein on 7 Dec 2008 23:42 In article <tqb3j4pmpsqj32hes94kb9pni1vaup6b34(a)4ax.com>, Whata Fool wrote: >bill.sloman(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 > 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. And the atmosphere has a lot of it anyway - 388 ppmv means about 6 kilograms per square meter of Earth. <SNIP from here> - Don Klipstein (don(a)misty.com)
From: Don Klipstein on 8 Dec 2008 00:06
In article <pan.2008.11.30.20.54.34.361748(a)REMOVETHISix.netcom.com>, Bill Ward wrote: >On Sun, 30 Nov 2008 07:13:33 -0800, bill.sloman wrote: > >> On 29 nov, 06:43, Bill Ward <bw...(a)REMOVETHISix.netcom.com> wrote: >>> 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:> >> >> <big snip - Bill Ward does go in for mindless repetition> >> >>> > 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. >>> >>> There's an excess of water vapor available to convect latent heat up to >>> the effective radiating altitude. >> >> The air at the effective radiating altitude is well below the freezing >> point of water - the earth radiates as if it is a black body at -14C, and >> while this is an average over all wavelengths (for wavelengths absorbed >> and re-radiated by CO2 the temperature has to be closer to -55C) it makes >> sense that the radiation appears to come from a layer where water vapour - >> the predominant greenhouse gas - has condensed out. >> >> The partial pressure of water vapour above the cloud tops is too low to >> convect any signficant latent heat higher > >You seem to be going to great lengths to repeat my points as though they >were your own. I'll take that as a compliment. Once the cloud has >condensed, its latent heat has radiated from the cloud tops, Radiation of the heat (latent or otherwise) does not occur the instantly. The air may descend somewhere else before losing all its heat to radiation. > and has a clear shot to space. Above the cloud tops, WV is gone, >radiation is effective, convection isn't needed. What about when CO2 is present? What about when cloud tops are low? >>> It's in the 10s of kW/m^2 compared to the 500W/m^2 max from surface >>>radiation. >> >> It was at the surface, where the partial pressure of water vapour is >> around 2300 Pa. The saturation vapour pressure has dropped to 603 Pa by >> the time the temperature has dropped to zero Celcius. It drops off even >> faster over ice, so it certainly isn't beating radiation at the >> effective emitting altitude. > >Assume at the surface boundary layer we have a thermal with a given >humidity and velocity. What do you think happens to a parcel of air, >and the energy it contains, as it rises? Keep in mind that matter and >energy are conserved. > >I can tell you, from direct observation, that it continues upward at a >relatively constant velocity until it reaches either a change in the >lapse rate, or the condensation altitude (cloud base). You need to >rethink your position to include that easily verifiable fact. You also >need to get out more. Try riding a sailplane in a thermal. Not that most of the world has thermals from surface to tropopause - those are thunderstorms. >> http://www.engineeringtoolbox.com/water-vapor-saturation-pressure-air-d_689.html >> >> http://www.answers.com/topic/dewpoint-jpg-1 >> >> http://faculty.matcmadison.edu/slindstrom/VaporPressure.doc > >Thanks for the supporting links. I may have posted a couple of them >before. > >>>The lower troposphere is translucent in the 15u band. How could CO2 >>>play any significant part, compared to radiation? Above the clouds, it >>>has a clear shot to >>> space. >> >> CO2 has both 5u and 15u absorbtion bands I would like to add that the 15 um band is significant at surface level temperatures. At 288 K, a blackbody has spectral power distribution about 71-72% of peak. >Please. Are you now claiming that the surface is radiating >significantly in the 5u band? You're the radiation expert, what BB >temperature would that represent? My BOE guess is about 300C, which >seems a bit unrealistic for Earth, At 288 K, a blackbody has spectral power distribution about 22% of peak at 5 um. There is some surface radiation in that band being absorbed by CO2 overhead. > especially at the effective radiation altitude. Looks like you've >reached the bottom of the barrel. > >> http://www.wag.caltech.edu/home/jang/genchem/infrared.htm >> >> What do you mean by "translucent"? > >Scattering rather than absorbing, like the frosted glass on a light bulb. >I was humoring you. I suspect the lower troposphere is nearly opaque to >the 15u band, and satellites are just seeing emission from the top layer. >It doesn't matter either way to the argument. > >> CO2 absorbs and retransmits infra-red radiation at specific lines >> within both bands, and this radiation won't have a "clear shot at space" >> until it gets high in the stratosphere. > >How much? And how much difference does it make in view of the negative >feedbacks involved in the convective transfer? Try considering the lower >troposphere as a variable (temperature sensitive) thermal resistance The majority of the troposphere that is lacking convection has thermal resistivity not collapsing until convection occurs. That portion of the tropospher has upward mobility in lapse rate. > and the region above the radiating layer as a relatively smaller, >slightly CO2 sensitive resistance. > >> CO2 is also disproportionately effective at broadening water vapour >> absorption lines, and this will be significant in the region close above >> the cloud tops where there's still some partial pressure of gaseous >> water to absorb and retransmit at water vapour's absorbtion lines. > >OK. Now use your radiative transfer model to compare that to the effect >of warming (lowering) the emitting layer a few degrees. Don't forget the >T^4 term. Lowering of the emitting layer is what happens if GHGs are reduced. Except the emitting layer will still have the temperature appropriate for 1/4 of the solar constant times ratio of solar absorption to emissivity of the radiating layer. >Sorry about the repetition, but it was worth it, since you have now >apparently caught on to what I was saying. I'm more pragmatic than >polite, I guess. - Don Klipstein (don(a)misty.com) |