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From: Don Klipstein on 22 Dec 2008 08:18 In article <pmmtj4dcourqpbg17rtm5oor0a9ic1sbl7(a)4ax.com>, Whata Fool wrote: >don(a)manx.misty.com (Don Klipstein) wrote: > >>In article <p2kgj4ppvnkeocqk0ddfqqclh7avkp0u67(a)4ax.com>, Whata Fool wrote: >>>bill.sloman(a)ieee.org wrote: >>> >>>>On 4 dec, 13:43, Whata Fool <wh...(a)fool.ami> wrote: >>>>> Â Â Â Not only that, but just the cooling of the solid surface by the >>>>> air in early morning and evaporation of the dew or frost may be a lot >>>>> more than the "forcing" averaged over 24 hours. >>>> >>>>All of which happens well below the effective emitting altitude, and >>>>is consequently irrelevant to the greenhouse effect. >> >> That is still radiational cooling. Adding GHGs increases the amount of >>absorptions/reradiations for radiated heat to escape from surface to >>space, and that will reduce radiational cooling of the surface. >> >>> The real "greenhouse effect" is in the energy transferred to the >>>N2 and O2 by convection with the surface, and on the planet with GHGs, >>>by molecular collisions with them. >> >> Yes indeed, effect of GHGs is to warm the N2 and O2 in the lower >>troposphere by warming the lower troposphere, and to cool the N2 and O2 in >>the stratosphere by cooling the stratosphere. >> >><SNIP beyone here to edit for space> >> >> - Don Klipstein (don(a)misty.com) > > Other than convection with the surface, the only way GHGs can cool >the lower troposphere N2 and O2 is to warm the GHGs there. > > I repeat, my exercise is about what the temperature of the N2 and >O2 would be without GHGs (and no water), compared with now. > > And isn't it clear and logical that whatever way the GHGs move >the temperature in the case of the present GHG and water concentration, >more GHGs would move it a little further. > The conclusion seems to be that GHGs cool the atmosphere, and >more GHGs would cool it a little more. GHGs as a whole cool the atmosphere above roughly maybe the 350 mb level and warm everything lower, especially the surface. The surface is receiving some radiation from GHGs in addition to that from the Sun. Earth's surface temperature is a lot warmer than it would be without GHGs. Consider Earth's average surface temperature now compared to that which would occur if it was warmed by incoming solar radiation and cooled by inimpeded outgoing radiation, and nothing else. It is warmer than that now because of GHGs. I expect increase of GHGs to make it warmer still. - Don Klipstein (don(a)misty.com)
From: Don Klipstein on 22 Dec 2008 08:51 In article <pan.2008.12.15.05.10.44.858752(a)REMOVETHISix.netcom.com>, Bill Ward wrote: >On Mon, 15 Dec 2008 01:11:16 +0000, Don Klipstein wrote: > >> In article <pan.2008.12.07.07.55.55.626493(a)REMOVETHISix.netcom.com>, Bill >> Ward wrote: >> >>>On Sun, 07 Dec 2008 05:45:26 +0000, Don Klipstein wrote: >>> >>>> In article <pan.2008.11.29.05.49.04.133668(a)REMOVETHISix.netcom.com>, >>>> Bill Ward wrote: >>>>>He may also be aware that increased water vapor lowers the condensation >>>>>altitude, >>>> >>>> Cloud bases lower if relative humidity rises. Relative humidity >>>> stays >>>> about the same if water vapor concentration is only commensurate with >>>> temperature rise. >>> >>>Interesting concept. I'm assuming the surface temperature determines the >>>absolute humidity, and the condensation altitude would be determined by >>>the lapse rate downward from the cloud tops (radiation layer). It seems >>>to me the surface temperature varies a lot more than the higher >>>altitudes. >> >> It sure does! In fact, at the pressure level of most of the tropical >> tropopause (around or a little over 100 mb), on average it is cooler over >> the equator than over the poles! >> >>>Is there any actual data on the altitude of the radiation layer that >>>radiates the most power? From what I've seen, it's mid troposphere, not >>>the tropopause. Are there any credible models of the individual >>>mechanisms from cloud tops to the tropopause? >> >> That I know much less about. However, over the range of wavelengths at >> which the surface produces a lot of thermal IR, the transparency of the >> atmosphere varies greatly. > >My thought is that it wouldn't take much of an increase of temperature >by lowering cloud tops (assuming the same cloud thickness) below >relatively dry air, to radiate quite a bit more power through the >tropopause. It seems to me this information should be available from >satellite images, but I haven't seen it mentioned. It does appear to me that clouds lower than the tops of tropical thunderstorms do radiate more then the tops of tropical thunderstorms do. The tops of tropical thunderstorms are very cold. That gets complicated by how much GHG is over lower clouds. Meanwhile, addition of GHGs would be expected to make thunderstorms slightly taller and their tops colder. >>>>> raising the radiation temperature, and increasing the emitted IR >>>>>energy by the 4th power radiation law. IOW, it's a negative feedback, >>>>>not positive. >>>> >>>> Radiation from cloud bases is toward Earth. >>> >>>I think that concept confuses people, at least me, when I first heard >>>it. >>> It appears at first glance you are claiming the cloud bases are warming >>>the surface, which is clearly impossible by the second law. The clouds >>>are colder than the surface, and energy can never radiate from cold to >>>hot. >> >> Cloud bases slow cooling of the surface in the usual case of cloud >> bases >> being cooler than the surface. There is radiation from surface to cloud >> base and radiation from cloud base to surface. The latter is less in >> the usual case of cloud base being cooler than surface, but that does >> subtract from net radiation from the surface. > >There's an example of a confusing statement. To me, the net surface >radiation is the outgoing surface radiation minus the incoming radiation >from the cloud base. Subtracting the cloud base radiation from the net >radiation seems to me like double counting it, or an unusual use of the >word "net". Was that a typo, or is it something you can explain? My explanation is that I am counting once - net radiation from the surface is radiation from surface minus what surface receives from cloud. That is less under clouds than under clear atmosphere. >>>A little more thought reveals the actual mechanism must be that some of >>>the radiation that comes from the surface can be considered to be >>>radiated back to maintain the (Tsource^4 - Ttarget^4) term in the >>>Stefan-Boltzmann equation. That still requires that the net heat flow >>>is outward, never inward (unless the surface is cooler). The upper >>>layers may reduce the cooling rate of the surface, but they can never >>>actually heat it. >>> >>>The _net_ radiation has to be from the surface to the clouds. >> >> It is. And since clouds emit some radiation towards the surface, and >> emit more radiation towards the surface than clear air does, they slow >> radiational cooling of the surface. > >Right. It slows the cooling, but the surface never increases its >temperature by radiation from a colder source. The surface is still warmer than without that downward radiation by cooling less. >>>> Meanwhile, increasing GHGs cools the lower stratosphere and raises >>>> the tropopause - cloud tops around the tropopause will be cooler. >>> >>>I'm not clear why. Could you explain why a cooler stratosphere raises >>>the tropopause? Is it because the tropopause is the top of convection, >>>so a colder stratosphere allows convection to continue higher before the >>>UV-O2, O3 inversion takes over? >>> >>>Thanks for your comments. >> >> The tropopause is generally the top of convection - although there is >> not convection under it everywhere. If the stratosphere is cooler, then >> the convection can go higher. >> >> The tropopause is highest in the tropics. Global circulation has air >> over the equator generally moving upward, since tropospheric temperature >> overall is warmest there. > >Wouldn't the tropical air moving upward be humid, and carrying a lot of >latent heat? It does. However, the tops of tropical thunderstorms are not much warmer than that level of the atmosphere outside them - in fact they are slightly cooler than most of the world's atmosphere at the same altitude and at the same pressure level. The latent heat would make a temperature difference when the air comes back down - since it would want to warm at the dry adiabatic lapse rate on the way down, while having cooled at the wet adiabatic lapse rate on the way up. As soon as cloudy air experiences much cooling by radiation, it descends, warms from adiabatic compression and clears. With most of the moisture rained out or snowed out before it has spent more than a few minutes near the tropopause, it does not have to descend much to clear. (Some air in thunderstorms does descend more quickly, with precipitation in it.) Then it has to be cooled by radiation as it descends while it is descending. Ability of clear air to radiate so that middle troposphere does not get much warmer outside of thunderheads than within them is necessary for them to keep on forming, or to form the next day. Some of the air rising in the ITCZ does not even descend locally - it descends in other parts of the world, as part of global atmospheric circulation. >> Where the upward motion actually exists and it does get localized to >> the hotspots where air rises most easily, the lapse rate makes a close >> approximation of the dry adiabatic one from the surface to the cloud >> base, and the wet adiabatic one from the cloud base to the cloud tops at >> the tropical tropopause. >> The tropical deep convection is in part forced by global circulation, >> and in part (especially on a local scale) natural convection from where >> the surface is warmer than elsewhere nearby. On a local scale, there is >> both updraft and downdraft, though in the intertropical convergence zone >> net air motion is upward. > >If warm wet air is going up, and cold, dry air is going down, the >"net" air motion would seem to be somewhat irrelevant, compared to the >latent heat transfer represented by up- and down-drafts in the convection >cells. Do you think climate models simulate that correctly? I'm thinking >of Trenberth's assumption that latent heat transfer can be accurately >estimated by from global precipitation estimates. How do we know some >of the falling condensate isn't evaporated again before it hits the >surface? It wouldn't take much to counter 1.5W/m^2. The bigger problem is increase of GHGs warming parts of the world that can be more easily warmed than tropics. Especially the portions of the polar regions where snow/ice cover changes when long term temperature changes - that is a positive feedback. Increase of water vapor is a positive feedback. Reduced ability of oceans to hold CO2 when they warm is a positive feedback. Most of the surface level troposphere there can warm plenty before convecting. The main negative feedback of warming specific to higher latitudes is that making the surface temperature more even will reduce the global circulation transferring heat from the topics to the more extreme latitudes. >> The air rises until it cools so much that it >> can't rise anymore, and some will descend locally and some will move >> poleward and descend somewhere outside the ITCZ. >> >> - Don Klipstein (don(a)misty.com) - Don Klipstein (don(a)misty.com)
From: Don Klipstein on 22 Dec 2008 09:22 In article <pan.2008.12.18.06.59.46.603610(a)REMOVETHISix.netcom.com>, Bill Ward wrote in part: >On Thu, 18 Dec 2008 03:27:28 +0000, Don Klipstein wrote: > >> In article <pan.2008.12.09.15.55.30.33517(a)REMOVETHISix.netcom.com>, Bill >> Ward wrote: >>>On Tue, 09 Dec 2008 06:03:54 +0000, Don Klipstein wrote: >>> >>>> In <pan.2008.12.02.00.19.03.512271(a)REMOVETHISix.netcom.com>, Bill Ward >>>> wrote: >>>>>On Mon, 01 Dec 2008 08:59:25 +0000, Don Klipstein wrote: >>>>> >>>>>> In <pan.2008.11.29.04.28.21.555150(a)REMOVETHISix.netcom.com>, Bill >>>>>> Ward said: >>>>>>>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. >>>>> >>>>>Then I repeat: Where did it go? Surely you're not claiming net energy >>>>>is moving from cold air to warm surface. The second law cops will come >>>>>and get you. >>>> >>>> Some gets radiated. Much ends up on surface farther from the tropics >>>> than where it came from. A little bit does end up on surface hotter >>>> than where it came from (in dry subtropical highs), but that is clearly >>>> greatly a minority. >>> >>>That would require a heat pump. Could you explain the mechanism? >> >> Global atmospheric circulation driven by troposphere being warmer in the >> tropics than around the poles but on a rotating planet gives us such >> things as the subtropical jetstreams and subtropical highs. >> >> The heatpump results, > >I was thinking more of an explanation of the physics involved in moving >heat from a cool spot to a hotter one. Like what the working fluid is, and >where the stages of the cycle take place. > >> and does indeed have a minority of the air >> ascending in the ITCZ descending to the surface outside the ITCZ hotter >> than cooler. From surface to roughly the 110 mb level, the average >> temperature is supposed to be colder where the air descends. The >> descending air could cool by radiation - when descended to levels of the >> atmosphere with below-avererage GHG overhead (due to being very dry). >> Extra heating at some altitudes (sometimes close to surface) results from >> descent warming at the greater dry adiabatic lapse rate except for such >> air cooling radiationally from its GHGs - which it has less of (due to >> being dry), though it has below-average extent of GHG overhead. The air in >> hotspots of subtropical highs could even get pushed down by local weather >> features, though when "that hot" has to be a small minority in order for >> the laws of thermodynamics to hold true. >> >> Meanwhile, the highest temperatures in Africa and in North America, also >> above sea level in North America, are quite far from the equator - I would >> dare say at least 27 degrees north latitude, maybe more like closer to 30. >> >>>>>> And greenhouse gases above the cloudtop will return to the cloud >>>>>> some of the cloud's thermal radiation. >>>>> >>>>>Not net radiation. The net energy flow is always from hot to cold. >>>>>Always. >>>> >>>> GHGs will add impedance to that flow. >>> >>>And latent heat transport will decrease the impedance. >> >> And increase thereof will decrease temperature difference between where >> the heat comes from and where the heat goes. Much of the air rising in >> "tropical deep convection" descends elsewhere in the world, > >Once the water vapor has been lifted and condensed, the latent heat has >been transferred. How can it be transferred downward? First the air has >to cool so it can sink. Is there any way other than radiation? It does radiate. And since sinking air tends to be clear, it has to do a lot of its radiation while clear in order to sink. The tops of tropical thunderstorms are at about the same temperature as the surrounding clear air at the same level. The lapse rate from cloud top level to cloud base level is close to the wet adiabatic one, and air tries to warm at the rate of the dry adiabatic one as it sinks. Radiation allows it to descend, mostly while it is descending. The radiation is often little enough for thunderstorms to warm most levels of the nearby troposphere with descending clear air. Limited ability of that air to sink limits the number of thunderstorms. Some of the air rising through tropical thunderstorms does not even descend locally, but elsewhere in the world - still doing so gradually as radiational cooling allows it to descend. >> since rising >> air in "tropical deep convection" is part of global atmospheric >> circulation. Global atmospheric circulation already contributes to the >> polar regions being warmer and the tropics being cooler than they >> otherwise would be. (Global oceanic circulation also does that - reduced >> exposure to global oceanic circulation makes the Red Sea and nearby areas >> hotter than otherwise-similar tropical areas.) > >Is it really that, or the fact that it gets a lot of sun and not much >cloud cover? That's probably part of the explanation also. However, I seem to think that there are other tropical areas with similar amounts of sunlight and cloud cover that don't get as warm. > Slowing the cooling rate is not heating. That still makes something warmer than it otherwise would be. >>>>>>> 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. >>> >>>If by "accumulating", you mean the temperature increases, yes. The >>>radiation is proportion to the 4th power of that temperature. >>> >>>>>Then it's sensible heat subject to upward convection. >>>> >>>> It won't convect much until warming achieves lapse rate achieving >>>> the relevant adiabatic one. >>> >>>And accumulating heat will raise the temperature until convection >>>begins. >>> >>>> Most of the atmosphere has lapse rate less than the relevant adiabatic >>>> one. >>> >>>Probably. Half of the atmosphere is in nighttime. Wouldn't you agree >>>most heat is transported to the radiative layer during the daytime, when >>>temperatures are higher? >> >> I would agree much more heat gets transported there during daytime >> than at nighttime. >> >> However, most of the world lacks cloud tops within 4 km of the 350 mb >> level, and a lot of the air gettinmg that high or higher manages to not >> lose a lot of heat by radiation before it descends - a lot of >> radiational cooling of air occurs where its descent requires cooling as >> it descends (One good example is polar vortices). > >Cooling doesn't have to take place equally all over the globe. Of course >some areas will cool less effectively than others. Shouldn't the emphasis >be on understanding the most effective mechanisms, rather than focusing on >places that don't play much of a part? Cooling is still significant in parts of the globe where it is less. And those happen to be parts of the world where there is little convection, and some of those have the positive feedback mechanism of variation of snow and ice cover with temperature. >>>>> The temperature is a function of the gas laws and the specific heat >>>>> of the air. Warming a parcel of gas doesn't "trap" any radiation. >>>> >>>> I did not say warming a parcel of gas makes it trap radiation. What >>>> I >>>> said was that if a parcel of gas was cooler than achieving radiation >>>> balance, it will warm from radiation. >>> >>>True. That warming assists convection. >> >> What if it warmed where the lapse rate was short of allowing >> convection? That describes at least 80% of the troposphere! > >What if the 20% where it does happen is enough? There seems to be general >agreement that climate models don't handle deep tropical convection all >that well. Yet that's where most of the cooling happens. It wouldn't >take much negative feedback to wipe out the estimated CO2 forcing. Except that tropical deep convection only cools the tropics. It does not cool the polar regions. - Don Klipstein (don(a)misty.com)
From: Don Klipstein on 22 Dec 2008 09:37 In <hj8kk4le5784bdo5pf3r64g5rda9h6mv7r(a)4ax.com>, Whata Fool said in part: >> I think that has been modelled already somewhere, and it may not take me >>long to find such a model. Expect much cooler, with a much lower >>tropopause. Expect the 350 mb level to have temperature close to what it >>has now, but to be in the stratosphere. > > What? How is the stratosphere defined? By lack water and water >vapor? > > Wouldn't the whole atmosphere be stratosphere if there was no water >or GHGs? >>water vapor is a greenhouse gas - currently having roughly double to a few >>times as much GHG effect as CO2 has now. >> >> - Don Klipstein (don(a)misty.com) > > > Does that infer that CO2 could ever have as much GHG effect as >water vapor? It would take 50 times as much. CO2 has 9-26% of GHG effect at current (or maybe recent) atmospheric concentrations. > But water cools the surface by at least 10 or 20 degrees, and >the phase change is a big part of that cooling process. I would beg to differ about surface being 10-20 degrees cooler on average when wet than dry. The Amazon rainforest and the nearby parts of the Atlantic are not 10-20 degrees cooler on average than the Sahara. > Doesn't the fact that water evaporation provide a lot of >cooling of the "surface" suggest that the surface would be warmer >without water or GHGs? The heat goes somewhere - it does not get destroyed. It becomes part of the burden of radiational cooling of the atmosphere by GHGs. Keep in mind that a blackbody in Earth's orbit, with a GHG-free atmosphere or none at all, would be cooler than Earth is now. And since Earth has thermal IR emissivity being a higher percentage than its absorption of solar radiation, with GHGs removed and albedo unchanged it would be colder than a blackbody. - Don Klipstein (don(a)misty.com)
From: Don Klipstein on 22 Dec 2008 09:45
In article <pan.2008.12.17.16.01.14.695665(a)REMOVETHISix.netcom.com>, Bill Ward wrote in part: >And Kr is used to increase the temperature of incandescent filaments. Why >don't you explain that one too? It involves convection and thermal >conductivity, not radiation. Krypton increases filament temperature for given filament dimensions and power input only in comparison to more thermally conductive gases, such as argon and the usual argon-nitrogen mixture. The same filament with same power input would be hotter still in a vacuum. - Don Klipstein (don(a)misty.com) |