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From: Don Klipstein on 25 Dec 2008 00:02 In <pan.2008.12.22.18.36.52.970615(a)REMOVETHISix.netcom.com>, B. Ward said: >On Mon, 22 Dec 2008 13:51:19 +0000, Don Klipstein wrote: > >> In <pan.2008.12.15.05.10.44.858752(a)REMOVETHISix.netcom.com>, B. W. said: >>>On Mon, 15 Dec 2008 01:11:16 +0000, Don Klipstein wrote: >>> >>>> In <pan.2008.12.07.07.55.55.626493(a)REMOVETHISix.netcom.com>, B W said: >>>> >>>>>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. > >Well, there is the WV hole at 10u, so most IR should get through. That hole is a minority of "Earthly thermal IR", despite having some significance of allowing significant thermal IR escaping to deep space non-stop before thousands or millions or a few billion light-years. That hole does get narrowed/filled to a bit of extent that is a bit significant if GHGs increase. Keep in mind that the rises and falls of the ice ages depend on strong positive feedback from slight changes of insolation at a critical range of Arctic and near-Arctic latitudes where one positive feedback mechanism (surface albedo) is especially relevant. 2 other positive feedbacks are concentration of CO2 and H2O vapor (both greenhouse gases) as a result of ocean warming. Significance of CO2 being a positive feedback mechanism and not merely a dependent variable is that during the few hundred thousand years before the Industrial Revolution, best determination is that atmospheric CO2 concentration laggwed worldwide temperature by about 800 years. But since the Industrial Revolution, worldwide temperature has actually lagged atmospheric CO2 concentration by a few years. >> 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. > >That much I agree on. The net is the difference between the outgoing and >incoming. The next sentence is the one that confuses me: "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." > >Didn't you subtract it once already to get the "net radiation" in the >first place? It sounds like you are subtracting it again from the net >radiation, but I don't think that's what you meant. Best at this moment I can say is that net outward radiation over cloudy areas is net radiation from cloud tops. Should the clouds have a higher amount of heat reception in any way, then the heat has to be radiated from elsewhere - at least sometimes from clear air. Now that analysis of the above gets more clear to me, subtraction of downward radiation by cloud bases from upward radiation by surface is what I would call single-counting. >>>>>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. Two quotation symbols per line with lack of fewer before uptick: Is that where scientific debate fades onto agreement and remaining continuation of debate is on other points? >>>>>> 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. > >And there's where the latent heat was deposited. The actual net latent >heat transferred would be the difference in the amount of water vapor >between the wet ascending and dryer descending air. Actually, with thunderhead-carrying air masses having an impressive rate of tundercloud-carrying altitudes having lapse rate much closer to the wet rather than the dry of the 2 adiabatic ones, it appears to me that the latent heat has to be radiated on the way down so that the upward-convected air can descend despite lapse rate well shor4t of the dry adiabatic one. Heck, for air rising in ITCZ thunderstorms, some of that flows to less-tropical latitudes mostly without clouds - to where (more usually) lapse rate is so low as to require radiational cooling of cloudless air for it to descend. Second place to that is mildly-extratropical areas getting hotter at surface and/or surface-level-troposphere than is the case dfor ITCZ - has to be a minority - probably both minority-intermittent and having their excessive temperature largely confined to *at least* below the 700 mb level, fair chance with most of the excessive temperature below the 850 mb level. >> (Some air in thunderstorms does descend more quickly, with precipitation >> in it.) > >Won't some of that entrained precipitation evaporate when it reaches >warmer air, then repeat the condensation process in an updraft? That means heat transfer does not get far in either latitude or longitude. >That's my beef with the Trenberth energy budget cartoon - he estimates >latent heat transfer from total global precipitation to the surface, which >is an absolute lower limit. There's a lot of water in all three phases >bouncing around inside thunderstorms, going both up and down at impressive >speeds. The net energy transfer has to be upward, and big. In thunderstorm zones, the energy transfer is to upper atmosphere at level lower than the anvil upper surfaces. The anviltops are where the updrafts have "run out of gas" - lacking any ability to be warmer than surrounding clear air at same altitude, even including latent heat. The latent heat comes back when the thunderstorm-updrafted air comes back down - as it must. And descending from anvil-cloud altitude, it tries to warm at the dry adiabatic lapse rate, while it cooled mostly at the lesser wet adiabatic lapse rate on the way up, and at that lower rate of cooling stopped rising when further riasing made it cooler than surrounding air at same level (whether altitude or pressure level - on scale that local, "same story". >Do you have any quantitative estimates on the recirculation of water in >thunderstorms? Like how many cycles on the average, or how much energy is >transferred per kg of water before it falls out of play? That sidetrack of the debate(s) I acknowledge honestly only by admitting that half an hour "research time" at late-evening-12/24 means I have low chance of coming up with numbers for that sidetrack any time soon. Since you like that sidetrack, can you mention a source supporting it good enough for me to either concede agreement or find grounds to dispute 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. > >I'd think there should be enough WV around to handle that. Clouds aren't >the only source of radiation. That point of where we argue I agree upon. It appears to me that honest scientific debates involve arguments pushing the debating parties to concede (by one side or the other) to where they agree, with debate continuing to where it should. I certainly think that radiation burden from this planet of ours has significant burden from "clear air" "lacking clouds overhead" to have "radiation outgo" matching "radiation income". (At this point, I would note as a future sidetrack that Wikipedia supports Earth and its atmosphere absorbing enouh solar radiation to be "thrown back out" at close enough to 255 Kelvin as for "representative radiation temperature". However, some of that is direct-to-space-from-much-warmer-surface, even if notably quite a minority - meaning atmospheric thermal IR outgo comes from colder. At this point, with surface "root-mean-4th_power" probably a goodly 290 K, I am so far in poor mood to "math things out further" to "at-this-point" consider the atmosphere to be "an appropriately weighted partial radiator" at around 240 K or so (my estimate when I get in a mood to swing the bat more). (http://en.wikipedia.org/wiki/File:Greenhouse_Effect.svg indicates that there is "in my words fair determination" that Earth and its atmosphere absorbs 235 watts per square meter of solar radiation, with 195 of that radiated from atmosphere and 40 of that from surface. I would like to add that intra-atmospheric heat flows despicted by that geraphic appear to me to include heat flows by convection) So if at this point the "effective radiation temperature of the atmosphere" is 240 K, that altitude in "standard atmosphere" (cooling at from worldwide-average-surface at "1-size-fits-all" wet adiabatic lapse rate of about 3.5 F per 1,000 feet until hitting tropopause) from 288 K surface indicates almost 25,000 feet or close to 7.5 km or close to hardly lower than the 350 mb level that I said before. >> 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. > >Doesn't that require the assumption that radiative transport is >more effective than convective transport? What about when there is also largely-horizontal heat transport involved? >> 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. > >Won't that keep the heat at higher tropical temperatures, where it can >radiate more effectively due to the T^4 term? One problem is that quite little of Earth's atmosphere below top of stratosphere is any colder than ITCZ-tropopause. Most of that little minority is in the Antarctic's "Polar Vortex" well after the relevant winter solstace and before it has greatly faded the following spring. Tropical warming (thankfully which I only expect to be minor compared to warming elsewhere in the world in response to increase of GHGs) will, for one thing, raise the tropical tropopause to a higher altitude that is even colder (despite surface warming) than the extreme cold that the current "tropical tropopause" already has. Elsewhere on this point, I expect that based on my past arguments that global warming in response to increase of GHGs will be disproportionately extratropical (and especially disproportionally in or near the Arctic), I expect the radiational cooling burden to become more even worldwide in response to heating becomeing more even worldwide due to mainly less-tropical latitudes increasing absorption of solar radiation in response to whatever "global warming" actually occurs. - Don Klipstein (don(a)misty.com)
From: Bill Ward on 25 Dec 2008 02:29 On Thu, 25 Dec 2008 05:02:17 +0000, Don Klipstein wrote: > In <pan.2008.12.22.18.36.52.970615(a)REMOVETHISix.netcom.com>, B. Ward said: >>On Mon, 22 Dec 2008 13:51:19 +0000, Don Klipstein wrote: >> >>> In <pan.2008.12.15.05.10.44.858752(a)REMOVETHISix.netcom.com>, B. W. >>> said: >>>>On Mon, 15 Dec 2008 01:11:16 +0000, Don Klipstein wrote: >>>> >>>>> In <pan.2008.12.07.07.55.55.626493(a)REMOVETHISix.netcom.com>, B W >>>>> said: >>>>> >>>>>>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. >> >>Well, there is the WV hole at 10u, so most IR should get through. > > That hole is a minority of "Earthly thermal IR", despite having some > significance of allowing significant thermal IR escaping to deep space > non-stop before thousands or millions or a few billion light-years. > > That hole does get narrowed/filled to a bit of extent that is a bit > significant if GHGs increase. Keep in mind that the rises and falls of > the ice ages depend on strong positive feedback from slight changes of > insolation at a critical range of Arctic and near-Arctic latitudes where > one positive feedback mechanism (surface albedo) is especially relevant. 2 > other positive feedbacks are concentration of CO2 and H2O vapor (both > greenhouse gases) as a result of ocean warming. > > Significance of CO2 being a positive feedback mechanism and not merely a > dependent variable is that during the few hundred thousand years before > the Industrial Revolution, best determination is that atmospheric CO2 > concentration laggwed worldwide temperature by about 800 years. I've seen that RC blog argument that CO2 lagging temperature signifies a positive feedback rather than the more obvious causual relation. They don't explain, however, exactly how the temperature can be made to stay down for 800 years while the CO2 stays high. Can you? > But since the Industrial Revolution, worldwide temperature has actually > lagged atmospheric CO2 concentration by a few years. The period from 1940 to 1975, and the last decade or so don't seem to fit in that pattern. One could also look back to 1200AD and see the temperature of the MWP raising CO2 levels now, 800 years later. > >>> 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. >> >>That much I agree on. The net is the difference between the outgoing >>and incoming. The next sentence is the one that confuses me: "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." >> >>Didn't you subtract it once already to get the "net radiation" in the >>first place? It sounds like you are subtracting it again from the net >>radiation, but I don't think that's what you meant. > > Best at this moment I can say is that net outward radiation over > cloudy areas is net radiation from cloud tops. > Should the clouds have a higher amount of heat reception in any way, > then the heat has to be radiated from elsewhere - at least sometimes > from clear air. > > Now that analysis of the above gets more clear to me, > subtraction of downward radiation by cloud bases from upward radiation > by surface is what I would call single-counting. That's included in the concept of "net', I believe. I think it's just a language issue. >>>>>>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. > > Two quotation symbols per line with lack of fewer before uptick: > > Is that where scientific debate fades onto agreement and remaining > continuation of debate is on other points? OK by me. >>>>>>> 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. >> >>And there's where the latent heat was deposited. The actual net latent >>heat transferred would be the difference in the amount of water vapor >>between the wet ascending and dryer descending air. > > Actually, with thunderhead-carrying air masses having an impressive > rate of tundercloud-carrying altitudes having lapse rate much closer > to the wet rather than the dry of the 2 adiabatic ones, it appears to > me that the latent heat has to be radiated on the way down so that the > upward-convected air can descend despite lapse rate well short of the > dry adiabatic one. > Heck, for air rising in ITCZ thunderstorms, some of that flows to > less-tropical latitudes mostly without clouds - to where (more > usually) lapse rate is so low as to require radiational cooling of > cloudless air for it to descend. > Second place to that is mildly-extratropical areas getting hotter at > surface and/or surface-level-troposphere than is the case for ITCZ - > has to be a minority - probably both minority-intermittent and having > their excessive temperature largely confined to *at least* below the > 700 mb level, fair chance with most of the excessive temperature below > the 850 mb level. Does that change anything I said above about the latent heat still being transferred upward and deposited as sensible heat? >>> (Some air in thunderstorms does descend more quickly, with >>> precipitation in it.) >> >>Won't some of that entrained precipitation evaporate when it reaches >>warmer air, then repeat the condensation process in an updraft? > > That means heat transfer does not get far in either latitude or > longitude. Why would that matter? Latent heat is being transferred upward, past some of the GHG layers. >>That's my beef with the Trenberth energy budget cartoon - he estimates >>latent heat transfer from total global precipitation to the surface, >>which is an absolute lower limit. There's a lot of water in all three >>phases bouncing around inside thunderstorms, going both up and down at >>impressive speeds. The net energy transfer has to be upward, and big. > > In thunderstorm zones, the energy transfer is to upper atmosphere at > level lower than the anvil upper surfaces. The anviltops are where the > updrafts have "run out of gas" - lacking any ability to be warmer than > surrounding clear air at same altitude, even including latent heat. > > The latent heat comes back when the thunderstorm-updrafted air comes > back down - as it must. After getting that cold, how much WV could the descending air have? Wouldn't it be pretty dry? I know that sometimes precipitation comes out of the anvil, leaving the latent heat behind. > And descending from anvil-cloud altitude, it tries to warm at the dry > adiabatic lapse rate, while it cooled mostly at the lesser wet adiabatic > lapse rate on the way up, and at that lower rate of cooling stopped > rising when further riasing made it cooler than surrounding air at same > level (whether altitude or pressure level - on scale that local, "same > story". Again, how could it have much WV after being so cold? > >>Do you have any quantitative estimates on the recirculation of water in >>thunderstorms? Like how many cycles on the average, or how much energy >>is transferred per kg of water before it falls out of play? > > That sidetrack of the debate(s) I acknowledge honestly only by > admitting that half an hour "research time" at late-evening-12/24 > means I have low chance of coming up with numbers for that sidetrack > any time soon. > > Since you like that sidetrack, can you mention a source supporting it > good enough for me to either concede agreement or find grounds to > dispute it? Not yet, but I'm working on 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. >> >>I'd think there should be enough WV around to handle that. Clouds >>aren't the only source of radiation. > > That point of where we argue I agree upon. > > It appears to me that honest scientific debates involve arguments > pushing the debating parties to concede (by one side or the other) to > where they agree, with debate continuing to where it should. Or agree to disagree until the issues become more clear. > I certainly think that radiation burden from this planet of ours has > significant burden from "clear air" "lacking clouds overhead" to have > "radiation outgo" matching "radiation income". I'm not exactly sure what you mean. There has to be long term radiative balance, but it seems to me we're a long ways from being able to be quantitative enough about the relative effect of the cooling mechanisms to make catastrophic claims like the AGWers. We can't even be sure of the sign currently. > (At this point, I would note as a future sidetrack that Wikipedia > supports Earth and its atmosphere absorbing enouh solar radiation to be > "thrown back out" at close enough to 255 Kelvin as for "representative > radiation temperature". > However, some of that is direct-to-space-from-much-warmer-surface, > even if notably quite a minority - meaning atmospheric thermal IR outgo > comes from colder. > At this point, with surface "root-mean-4th_power" probably a goodly > 290 K, I am so far in poor mood to "math things out further" to > "at-this-point" consider the atmosphere to be "an appropriately weighted > partial radiator" at around 240 K or so (my estimate when I get in a > mood to swing the bat more). It seems like that is an item that should be obtainable by direct satellite measurement. > > (http://en.wikipedia.org/wiki/File:Greenhouse_Effect.svg indicates > that there is "in my words fair determination" that Earth and its > atmosphere absorbs 235 watts per square meter of solar radiation, with > 195 of that radiated from atmosphere and 40 of that from surface. > I would like to add that intra-atmospheric heat flows despicted by > that geraphic appear to me to include heat flows by convection) I don't see anything specific about convection. > > So if at this point the "effective radiation temperature of the > atmosphere" is 240 K, that altitude in "standard atmosphere" (cooling at > from worldwide-average-surface at "1-size-fits-all" wet adiabatic lapse > rate of about 3.5 F per 1,000 feet until hitting tropopause) from 288 K > surface indicates almost 25,000 feet or close to 7.5 km or close to > hardly lower than the 350 mb level that I said before. Until people can get closer than a range of 240K to 255K on the effective radiating temperature, it seems pointless to worry about 1.5W/m^2 of "CO2 forcing". > >>> 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. >> >>Doesn't that require the assumption that radiative transport is more >>effective than convective transport? > > What about when there is also largely-horizontal heat transport > involved? Why would the horizontal component matter? The energy is lifted above much of the GHGs, then deposited. It has to radiate and cool somewhere. > >>> 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. >> >>Won't that keep the heat at higher tropical temperatures, where it can >>radiate more effectively due to the T^4 term? > > One problem is that quite little of Earth's atmosphere below top of > stratosphere is any colder than ITCZ-tropopause. Most of that little > minority is in the Antarctic's "Polar Vortex" well after the relevant > winter solstace and before it has greatly faded the following spring. > > Tropical warming (thankfully which I only expect to be minor compared > to > warming elsewhere in the world in response to increase of GHGs) will, > for one thing, raise the tropical tropopause to a higher altitude that > is even colder (despite surface warming) than the extreme cold that the > current "tropical tropopause" already has. > > Elsewhere on this point, I expect that based on my past arguments that > global warming in response to increase of GHGs will be > disproportionately extratropical (and especially disproportionally in or > near the Arctic), I expect the radiational cooling burden to become more > even worldwide in response to heating becomeing more even worldwide due > to mainly less-tropical latitudes increasing absorption of solar > radiation in response to whatever "global warming" actually occurs. What's it doing now? We seem to be cooling at the moment.
From: Whata Fool on 25 Dec 2008 07:07 don(a)manx.misty.com (Don Klipstein) wrote: >In <pan.2008.12.22.18.36.52.970615(a)REMOVETHISix.netcom.com>, B. Ward said: >>On Mon, 22 Dec 2008 13:51:19 +0000, Don Klipstein wrote: >> >>> In <pan.2008.12.15.05.10.44.858752(a)REMOVETHISix.netcom.com>, B. W. said: >>>>On Mon, 15 Dec 2008 01:11:16 +0000, Don Klipstein wrote: >>>> >>>>> In <pan.2008.12.07.07.55.55.626493(a)REMOVETHISix.netcom.com>, B W said: >>>>> >>>>>>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. >> >>Well, there is the WV hole at 10u, so most IR should get through. > > That hole is a minority of "Earthly thermal IR", despite having some >significance of allowing significant thermal IR escaping to deep space >non-stop before thousands or millions or a few billion light-years. Do you make brain slips like that very often? How long is a light year now?
From: Don Klipstein on 26 Dec 2008 00:27 In article <pan.2008.12.22.19.00.03.198314(a)REMOVETHISix.netcom.com>, Bill Ward wrote: >On Mon, 22 Dec 2008 14:22:58 +0000, Don Klipstein wrote: > >> 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. > >Through relatively warmer air, increasing the T^4 term. > >> 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. > >Isn't that an example of negative feedback? When enough energy has been >lifted to result in a stable lapse rate, the cooling stops. That >stabilizes the temperature. Tropical thunderstorm development tends to warm the atmosphere - below the tropopause - while making the warmer air drier. The lapse rate in the clear air around the thunderheads increases as a result of the convection - but the air remains stable. The lapse rate increases a bit past the wet adiabatic one, while the air is dry. The middle and lower troposphere then have to cool by radiation in order to allow air at surface level to convect upward to form more thunderstorms - sometimes not until the next day. The stabilization is that thunderstorm formation slows when temperature of the troposphere much past surface level is as warm as possible compared to the surface (and surface-level troposphere) for warming by convection from the surface. Thunderstorms lose population density if they transfer latent heat to the surrounding clear air faster than the surrounding clear air can radiate it. >> 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. > >Why would it matter where or when it radiates the heat? The surface has >been cooled by evaporation, and the energy has no way to go but up. Or poleward - net updraft in the ITCZ is part of global atmospheric circulation. >>>> 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. > >Only if it's being heated by something else. - Such as heating by what has already always been supplying heat. Same heat input, reduce effectiveness of cooling - that place gets warmer than before. >>>>>>>>> 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. > >It's a matter of degree. We seem to agree that most of the cooling occurs >in the tropics, and the quantitative importance of the poles still seems >to be uncertain, especially if you can see negative feedback at work in >the convection mechanism. The polar regions just seem kind of dull and >thus easier to model. I see the convective negative feedback being stabilization of population density of thunderstorms to an extent where surrounding clear air radiates the latent heat released in the thunderstorms. When thunderstorm population is "excessive", then middle and troposphere and most of the lower troposphere (in the convective area) get too warm to allow humid surface air to rise into, while too dry to allow convection despite having lapse rate greater than the wet adiabatic one. The thunderstorms are balanced by radiation from the air that was updrafted through them - mostly while it is descending and clear. (This is a bit oversimplified - some precipitation does blow out the tops of thunderstorms, much of that bit being snow falling from anvils - cooling the air a mile or 2 below the anvils. Thunderstorms also have precipitation falling into low-dewpoint air, cooling it and allowing it to descend while warming at only the wet adiabatic lapse rate and descending far (sometimes also fast) while remaining cooler than surrounding air. Yet the upward heat transfer in tropical thunderstorms fails to make the tropical tropopause warmer than air at same altitude or pressure level outside the ITCZ - it gets so cold from rising so high that radiation balance slowly warms it. The latent heat comes out as radiation while it descends.) >>>>>>> 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. > >When I look at the globe, I see a lot more tropical region than polar >region. I see tropical deep convection not even cooling the tropics as a whole, but merely the ITCZ. Heck, global circulation also cools the ITCZ. Cooling of tropics outside ITCZ relies less on convection and more on cool advection from extratropical areas. That is a matter of global circulation. If for some reason the troposphere did not support a lapse rate favoring thunderstorms in the ITCZ, then I would expect the ITCZ to be largely filled by a band of more stratiform raincloud - possibly somewhat resembling the lowest few thousand feet of many supercells (though probably ending up much thicker than a few thousand feet). Along that sidetrack: It is at least somewhat common for supercells to exist where the first few thousand feet above the cloud base is stable air (lapse rate probably slightly less than the wet adiabatic one). One factor favoring the spectacular mighty ones of the supercells, mostly found in the Great Plains "Tornado Alley", is lower troposphere supressing thunderstorms and middle and upper troposphere having lapse rate well above the wet adiabatic one. First hotspot convecting past the hurdle blows up like a hydrogen bomb, and at least some of the net updraft from that descends nearby, warming the middle troposphere to maintain the hurdle to competitors to the existing storm for convective energy. Another factor essential for supercells is windsheer - wind velocity varying significantly with altitude, in a way to have the thunderstorm's precipitation mostly fall somewhere outside the updraft forming the precipitation so as to not suicidally bite the hand feeding it. That increases longevity of an individual updraft - a factor favoring tornadoes - and also helps the intensity of the updraft a little (good for tornadoes and large hail). But I have digressed along a line explaining stratiform cloud forming in air being lifted upward vertically, on some hypothetical alteration of Earth with ITCZ having lapse rate short of the wet adiabatic one, forced to closer to the wet adiabatic one by ITCZ uplifting by global circulation. - Don Klipstein (don(a)misty.com)
From: Bill Ward on 26 Dec 2008 03:08
On Fri, 26 Dec 2008 05:27:27 +0000, Don Klipstein wrote: > In article <pan.2008.12.22.19.00.03.198314(a)REMOVETHISix.netcom.com>, Bill > Ward wrote: >>On Mon, 22 Dec 2008 14:22:58 +0000, Don Klipstein wrote: >> >>> 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. >> >>Through relatively warmer air, increasing the T^4 term. >> >>> 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. >> >>Isn't that an example of negative feedback? When enough energy has been >>lifted to result in a stable lapse rate, the cooling stops. That >>stabilizes the temperature. > > Tropical thunderstorm development tends to warm the atmosphere - below > the tropopause - while making the warmer air drier. The lapse rate in the > clear air around the thunderheads increases as a result of the convection > - but the air remains stable. The lapse rate increases a bit past the wet > adiabatic one, while the air is dry. > > The middle and lower troposphere then have to cool by radiation in order > to allow air at surface level to convect upward to form more thunderstorms > - sometimes not until the next day. That sounds like you agree that convection cools the surface by lifting latent heat to an altitude where it can radiate to space. > > The stabilization is that thunderstorm formation slows when > temperature > of the troposphere much past surface level is as warm as possible > compared to the surface (and surface-level troposphere) for warming by > convection from the surface. Thunderstorms lose population density if > they transfer latent heat to the surrounding clear air faster than the > surrounding clear air can radiate it. Still cooling the surface by convecting latent heat, but slowing as the surface cools and becomes more stable. That sounds like negative feedback to me. Do you agree? >>> 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. >> >>Why would it matter where or when it radiates the heat? The surface has >>been cooled by evaporation, and the energy has no way to go but up. > > Or poleward - net updraft in the ITCZ is part of global atmospheric > circulation. But not downward, until it arrives over warmer air through which it can sink, cooling the surface. >>>>> 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. >> >>Only if it's being heated by something else. > > - Such as heating by what has already always been supplying heat. > > Same heat input, reduce effectiveness of cooling - that place gets > warmer than before. OK, I'll agree with that. It's different from implying that the upper layers radiate heat to the surface, warming it. The net heat flow is still upward, from warm to cold. >>>>>>>>>> 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. >> >>It's a matter of degree. We seem to agree that most of the cooling >>occurs in the tropics, and the quantitative importance of the poles >>still seems to be uncertain, especially if you can see negative feedback >>at work in the convection mechanism. The polar regions just seem kind >>of dull and thus easier to model. > > I see the convective negative feedback being stabilization of > population density of thunderstorms to an extent where surrounding > clear air radiates the latent heat released in the thunderstorms. > When thunderstorm population is "excessive", then middle and > troposphere and most of the lower troposphere (in the convective area) > get too warm to allow humid surface air to rise into, while too dry to > allow convection despite having lapse rate greater than the wet > adiabatic one. The thunderstorms are balanced by radiation from the > air that was updrafted through them - mostly while it is descending > and clear. That sounds like what I was saying, perhaps in more precise terms. At any rate, it's negative feedback, stabilizing the surface temperature. > (This is a bit oversimplified - some precipitation does blow out the > tops of thunderstorms, much of that bit being snow falling from anvils - > cooling the air a mile or 2 below the anvils. Which Trenberth doesn't count as latent heat transfer. > Thunderstorms also have precipitation falling into low-dewpoint air, > cooling it and allowing it to descend while warming at only the wet > adiabatic lapse rate and descending far (sometimes also fast) while > remaining cooler than surrounding air. Again, uncounted by Trenberth. > Yet the upward heat transfer in tropical thunderstorms fails to make > the tropical tropopause warmer than air at same altitude or pressure > level outside the ITCZ - it gets so cold from rising so high that > radiation balance slowly warms it. The latent heat comes out as > radiation while it descends.) How can it contain any more latent heat if it has been so cold? Wouldn't any WV already have condensed to cloud at lower levels? >>>>>>>> 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. >> >>When I look at the globe, I see a lot more tropical region than polar >>region. > > I see tropical deep convection not even cooling the tropics as a > whole, > but merely the ITCZ. Heck, global circulation also cools the ITCZ. > Cooling of tropics outside ITCZ relies less on convection and more on > cool advection from extratropical areas. > > That is a matter of global circulation. If for some reason the > troposphere did not support a lapse rate favoring thunderstorms in the > ITCZ, then I would expect the ITCZ to be largely filled by a band of > more stratiform raincloud - possibly somewhat resembling the lowest few > thousand feet of many supercells (though probably ending up much thicker > than a few thousand feet). > Along that sidetrack: It is at least somewhat common for supercells > to exist where the first few thousand feet above the cloud base is > stable air (lapse rate probably slightly less than the wet adiabatic > one). One factor favoring the spectacular mighty ones of the > supercells, mostly found in the Great Plains "Tornado Alley", is lower > troposphere supressing thunderstorms and middle and upper troposphere > having lapse rate well above the wet adiabatic one. First hotspot > convecting past the hurdle blows up like a hydrogen bomb, and at least > some of the net updraft from that descends nearby, warming the middle > troposphere to maintain the hurdle to competitors to the existing storm > for convective energy. Sounds like a lot more energy in the convection than in any low level radiative transfer. > Another factor essential for supercells is windsheer - wind velocity > varying significantly with altitude, in a way to have the thunderstorm's > precipitation mostly fall somewhere outside the updraft forming the > precipitation so as to not suicidally bite the hand feeding it. That > increases longevity of an individual updraft - a factor favoring > tornadoes - and also helps the intensity of the updraft a little (good > for tornadoes and large hail). > > But I have digressed along a line explaining stratiform cloud forming > in air being lifted upward vertically, on some hypothetical alteration > of Earth with ITCZ having lapse rate short of the wet adiabatic one, > forced to closer to the wet adiabatic one by ITCZ uplifting by global > circulation. What we need are some realistic quantitative figures for the energy distributions, rather than crude qualitative ones. Trenberths estimate for latent heat transfer can't be right, because he includes only that condensed WV that reaches the surface as precipitation. Yet his figure is widely referenced. |