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Post by radiant on Sept 20, 2009 18:14:54 GMT
Update: Interestingly Nitrogen and Oxygen are very poor emitters of infrared radiation. www.irgas.com/ftir_spectroscopy.htmlJohn Tyndall in the 1860's had already observed that the Ozone in ordinary sea level oxygen absorbed more IR than all of the oxygen. An oxygen nitrogen and argon atmosphere without water and C02 would be warm with no other way of being cooled other than via reaching the cool earths surface. But the surface at night would radiate strongly to space and be very cold. Space is very very cold. The clear day sky in texas is however warmer at 0 C. mynasadata.larc.nasa.gov/P18.htmlThe gas of water is overwhelming the most massive warming influence in our atmosphere to make the sky temperature rise higher than the nearly absolute zero of space. Even in the exstremely dry air of Antarctica which has almost no 'gas of water' above the surface, the surface receives more IR from water in the atmosphere than all other sources combined. This atmospheric water vapour as a gas is a light atmospheric gas. Therefore in normal temperatures from the damp surface of the earth a column of water rises to enormous altitudes to the stratosphere. However the 'Antarctic effect' is also in play cold air holds almost no water vapour. So there is a circulation system of water in play. Water must be a significant driver of air flows around the planet also since water takes air with it to altitude where the water rains or snows down or falls out as fine ice very high in the atmosphere. John Tyndall had some thoughts about water as a thermal blanket in 1865 where much of the earths surface has a fine layer of water on it at night that is cooling by radiation to space. The radiation that water emitts being perfectly made to be perfectly absorbed by atmospheric water. Any other terrestial radiation then has to pass thru water to get past the ability of atmospheric water to absorb the water frequencies. Overall the air even with water has a very poor ability to emit heat but there is a massive amount of air around us. Even farm tractors are quoted with all up weights as factory specified that do not include inflated tyres C02 returns a tiny fraction of the atmospheres energy back to earth but is playing a role there somewhere. As I learn more i will edit this post. Edits: John Tyndall 1865 On Radiationbooks.google.com/books?id=nTQDAAAAQAAJ&pg=PP7#v=onepage&q=&f=falseJohn Tyndall 1872 Heat considered as a mode of motion books.google.com/books?id=35c5AAAAcAAJ&pg=PR3#v=onepage&q=&f=false
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Post by jurinko on Sept 20, 2009 18:49:11 GMT
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Post by socold on Sept 20, 2009 19:02:22 GMT
The Wood just proves that glasshouses don't heat by trapping IR.
The glass is absorbing an equal amount of IR from above as from below and emitting an equal amount of IR up and down. The same flows are in place whether glass is there or not.
The difference with the greenhouse effect is that the IR absorption and emission is spread over a declining temperature gradient. I guess if you had a 1km high greenhouse so that the glass at the ceiling was about 6.5K cooler than the surface this would demonstrate the difference.
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Post by radiant on Sept 20, 2009 19:44:33 GMT
The Wood just proves that glasshouses don't heat by trapping IR. The glass is absorbing an equal amount of IR from above as from below and emitting an equal amount of IR up and down. The same flows are in place whether glass is there or not. The difference with the greenhouse effect is that the IR absorption and emission is spread over a declining temperature gradient. I guess if you had a 1km high greenhouse so that the glass at the ceiling was about 6.5K cooler than the surface this would demonstrate the difference. The glass is absorbing an equal amount of IR from above as from below and emitting an equal amount of IR up and down. The same flows are in place whether glass is there or notThat seems wrong to me. From the first exposure to sunlight the glass absorbs 'no' radiation from above and absorbs 'all' longwave radiation from below. The temperature of the glass must therefore be in some manner proportional to the amount of heat that is not transmitted. In fact very little heat is being absorbed as far as i know because the glass does not get particularly hot on the inside? What woods reveals is the relative importance of convection to warm the atmosphere . The difference with the greenhouse effect is that the IR absorption and emission is spread over a declining temperature gradient.I dont understand this comment. Can you elaborate please? Emission at altitude becomes less relevant because high temperature radiation from very little matter cannot create sufficient radiation to warm a much more massive object even though the emission shows those molecules are hot. Intensity of emission is also important to determine warming of another object. To warm the earth something fairly massive has to be radiating with considerable intensity. The obvious candidate is the saturated air water mixture at the very surface of nearly all soils and plants or at least in the lower atmosphere - we already know that the atmosphere itself just gets warm anyway by convection and wants to stay that way without being cooled by the earth or by water or C02 As for a larger experiment: If you ever have to work at a high ceiling you notice that it is much hotter up there than down below. To get results from an experiment at small scale you would need to mimic the difficulty hot air has in rising thru the enormous relative mass of the atmosphere so that heat spreads sideways before it eventually penetrates the colder air above as it progressively builds up convection layers that are capable of bulging away from the surface and moving the enormous mass of air above to one side as it rises. On earth air tends to create thermals of convection where there are ground features of one kind or another. Woods tell us a few things 1. The principal method of warming the air is via convection at the surface. 2. The air has a poor ability to radiate heat when near the surface relative to the amount of heat it gains via convection With some imagination, Woods greenhouse with NaCL or maybe even just plastic? sheets would form the basis of an interesting atmospheric experiment for different concentrations of water and C02 if baffles were in place to slowdown convection and air could be taken from the top of the greenhouse via another route back to part of the surface covered with a low emissivity material without any additional mechanical means of circulating the air. It would be a simple and cheap experiment. Obviously once baffles were in place the greenhouse would be massively hotter at the surface than higher in the atmosphere present because the reduced flow thru the greenhouse would give the air time to be cooled by radiation from the water and C02. You could then play with the water and co2 concentrations Sideways facing simple cooled radiometers as thermometers in tubes surrounded by ice baths (a simple tube with an IR transparant cover surrounded by a larger diameter tube with ice and water) could then measure the amount of radiated heat coming from each layer of the greenhouse where the opposite side of the greenhouse was insulated and covered with aluminium foil - something like that Humidifiers could alter the humidity between baffles also to mimic the troposphere? Even a low budget could come up with something reasonable i think?
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Post by steve on Sept 21, 2009 11:24:55 GMT
My understanding is:
O2 does radiate and absorb energy in the microwave range - this is what the temperature observing satellites look at. The earth does emit at these wavelengths, but not very much.
Therefore, without CO2, H20, CH4 etc. the atmosphere would be colder because more of the radiation from the surface would escape to space, and less of it would warm the atmosphere. I guess conduction would be proportionately more important as a mechanism for warming the atmosphere, but whether it becomes significant or not, I don't know.
The temperature profile of the atmosphere would be, as now, warmer at the surface and cooling as you rise since this is determined by the adiabatic lapse rate (if the atmosphere continues to be convectively mixed).
The warmth above the tropopause relates to absorption of solar UV radiation by ozone etc. I guess a different atmospheric composition means a different amount and distribution of ozone and other reactive gases due to differing atmospheric chemistry, a different tropopause height as well as the different rate of cooling of the tropopause caused by a lack of "greenhouse" gases. This stretches the thought experiment somewhat.
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Post by radiant on Sept 21, 2009 15:51:15 GMT
My understanding is: O2 does radiate and absorb energy in the microwave range - this is what the temperature observing satellites look at. The earth does emit at these wavelengths, but not very much. Therefore, without CO2, H20, CH4 etc. the atmosphere would be colder because more of the radiation from the surface would escape to space, and less of it would warm the atmosphere. I guess conduction would be proportionately more important as a mechanism for warming the atmosphere, but whether it becomes significant or not, I don't know. The temperature profile of the atmosphere would be, as now, warmer at the surface and cooling as you rise since this is determined by the adiabatic lapse rate (if the atmosphere continues to be convectively mixed). The warmth above the tropopause relates to absorption of solar UV radiation by ozone etc. I guess a different atmospheric composition means a different amount and distribution of ozone and other reactive gases due to differing atmospheric chemistry, a different tropopause height as well as the different rate of cooling of the tropopause caused by a lack of "greenhouse" gases. This stretches the thought experiment somewhat. From what i understand: Adiabatic lapse rate does not apply to air that is mixedIt applies to a parcel of air or thermal of air that is rising that is unmixed and is expanding as it rises thru the other cooler air that surrounds it Lapse rate is just a description of a fall in termperature with altitude which may or many not apply to an atmosphere. It applies to earths atmosphere in the troposphere. As i understand it you have to be careful with adiabatic temperature changes because as the gas expands there is less material to indicate the amount of heat but the actual emission temperature of the material might remain the same. Emmission temperatures at altitude can therefore be rather meaningless in climate terms since there is proportionally much less material to give intensity that can warm masses which are greater. But this is an area that i think needs more contemplation and feedback Without green house gases the temperature of the air would tend to increase with altitude and this process of warmer air rising from the surface would continue until the air was more or less the same temperature but the earths surface would be cooler since no heat returned to earth via radiation and any passed to the atmosphere would act to cool the earth. The atmosphere would just be hot unless cooled by the cold earth - which would happen at night. By day the air would be very hot at the surface and travel up thru the already warm air
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Post by steve on Sept 21, 2009 16:30:19 GMT
The thermodynamics is based on theoretical parcels of air rising, and the parcels expanding and cooling. They will only rise if they remain a bit warmer than the surrounding air.
Unmixed parcels of air, though, don't exist - the rising and falling of "parcels" leads to a mixing of the atmosphere and the rate of cooling with the rising (which is not very dependent on the gas composition - except for water vapour) sets the average temperature profile.
In contrast (which is why I mentioned the need for convective mixing) if the atmosphere were stable such that no parcels rose or fell then the temperature profile would be different as it would be defined by radiation rather than convection (as happens in the stratosphere and some stellar atmospheres). I was leaving open the possibility that for some reason the N2/O2 atmosphere might end up being resistant to convective mixing.
In short - if convection is important in the theoretical O2/N2 atmosphere I think there *will* be a similar lapse rate to our current dry adiabatic lapse rate of 10C per kilometre. If not, I don't know what would happen as the radiation processes would need to be modelled to understand them.
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Post by radiant on Sept 21, 2009 17:26:15 GMT
The thermodynamics is based on theoretical parcels of air rising, and the parcels expanding and cooling. They will only rise if they remain a bit warmer than the surrounding air. Unmixed parcels of air, though, don't exist - the rising and falling of "parcels" leads to a mixing of the atmosphere and the rate of cooling with the rising (which is not very dependent on the gas composition - except for water vapour) sets the average temperature profile. In contrast (which is why I mentioned the need for convective mixing) if the atmosphere were stable such that no parcels rose or fell then the temperature profile would be different as it would be defined by radiation rather than convection (as happens in the stratosphere and some stellar atmospheres). I was leaving open the possibility that for some reason the N2/O2 atmosphere might end up being resistant to convective mixing. In short - if convection is important in the theoretical O2/N2 atmosphere I think there *will* be a similar lapse rate to our current dry adiabatic lapse rate of 10C per kilometre. If not, I don't know what would happen as the radiation processes would need to be modelled to understand them. You need to think about this some more. A parcel of air large enuf to penetrate the colder air above it, is a mass of tonnes of air that begins expanding as soon as it begins rising. Therefore it is resistant to mixing with the air around it because at the edges it has momentum as a separate mass of air that is moving outwards and upwards. An atmosphere that does not emit radiation will behave like an insulated water tank that is heated at the bottom. Heat will rise eventually because the lower surface will be enormously relatively hot and once the heat has risen it will very risistant to descending thru the colder denser air below Temperature inversions tend to form when for example an area of high pressure air is no longer expanding and is now descending while still qualifying as high pressure air so that the colder down moving air acts as a mass with momentum that prevents the warmer air below from penetrating it. Thermally stable air that is hot at the surface like this needs to be replaced by a low which is an entirely separate mass of air with its own separate momentum before thermals can begin to form to create puffy cumulous clouds In short - if convection is important in the theoretical O2/N2 atmosphere I think there *will* be a similar lapse rate to our current dry adiabatic lapse rate of 10C per kilometre.I think you are mixing things up. In conventional lower altitudes on earth Convection can happen with mixing of air and this slows down the rate of rise of the warmer air and dilutes the air and creates additional cooling by conduction as the masses mix But Thermals or parcels usually associate with a local hotspot happen without mixing of air and 'transport' an ascending expanding separate mass of air up thru the colder surrounding air of all one mass with its own momentum and wind speed. The colder air with wind speed acts upon the bubbles or tube of rising air from the surface hotspot like a wind acts upon a truck moving down the road, but the parcel or truck has momentum and forces that takes it in a different direction to the colder air moving sideways around it. For this reason a glider pilot can find a relatively small parcel of air near the surface that has separated from the surface and center in it and continue rising with it to the cloud base thousands of feet higher. Another pilot seeing him rise can enter the air below the rising pilot and find he cannot rise. Similarly another pilot above the rising pilot has to wait for the rising pilot to get to him before he can rise with the rising pilot.
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Post by radiant on Sept 21, 2009 17:28:21 GMT
The thermodynamics is based on theoretical parcels of air rising, and the parcels expanding and cooling. They will only rise if they remain a bit warmer than the surrounding air. Unmixed parcels of air, though, don't exist - the rising and falling of "parcels" leads to a mixing of the atmosphere and the rate of cooling with the rising (which is not very dependent on the gas composition - except for water vapour) sets the average temperature profile. In contrast (which is why I mentioned the need for convective mixing) if the atmosphere were stable such that no parcels rose or fell then the temperature profile would be different as it would be defined by radiation rather than convection (as happens in the stratosphere and some stellar atmospheres). I was leaving open the possibility that for some reason the N2/O2 atmosphere might end up being resistant to convective mixing. In short - if convection is important in the theoretical O2/N2 atmosphere I think there *will* be a similar lapse rate to our current dry adiabatic lapse rate of 10C per kilometre. If not, I don't know what would happen as the radiation processes would need to be modelled to understand them. You need to think about this some more. A parcel of air large enuf to penetrate the colder air above it, is a mass of tonnes of air that begins expanding as soon as it begins rising. Therefore it is resistant to mixing with the air around it because at the edges it has momentum as a separate mass of air that is moving outwards and upwards. An atmosphere that does not emit radiation will behave like an insulated water tank that is heated at the bottom. Heat will rise eventually because the lower surface will be enormously relatively hot and once the heat has risen it will very risistant to descending thru the colder denser air below Temperature inversions tend to form when for example an area of high pressure air is no longer expanding and is now descending while still qualifying as high pressure air so that the colder down moving air acts as a mass with momentum that prevents the warmer air below from penetrating it. Thermally stable air that is hot at the surface like this needs to be replaced by a low which is an entirely separate mass of air with its own separate momentum before thermals can begin to form to create puffy cumulous clouds In short - if convection is important in the theoretical O2/N2 atmosphere I think there *will* be a similar lapse rate to our current dry adiabatic lapse rate of 10C per kilometre.I think you are mixing things up. In conventional lower altitudes on earth Convection can happen with mixing of air and this slows down the rate of rise of the warmer air and dilutes the air and creates additional cooling by conduction as the masses mix But Thermals or parcels usually associated with a local hotspot happen without mixing of air and 'transport' an ascending expanding separate mass of air up thru the colder surrounding air of all one mass with its own momentum and wind speed. The colder air with wind speed acts upon the bubbles or tube of rising air from the surface hotspot like a wind acts upon a truck moving down the road, but the parcel or truck has momentum and forces that takes it in a different direction to the colder air moving sideways around it. For this reason a glider pilot can find a relatively small parcel of air near the surface that has separated from the surface and center in it and continue rising with it to the cloud base thousands of feet higher. Another pilot seeing him rise can enter the air below the rising pilot and find he cannot rise. Similarly another pilot above the rising pilot has to wait for the rising pilot to get to him before he can rise with the rising pilot. At other times rather than a bubble it is more like a tube of air that seems connected to the surface but even so in that tube you move up relative to the colder air around you - hence adiabatic. All cumulus clouds are an indication of these kinds of parcels that have rapidly moved from the surface as descrete masses of air. Another kind of parcel creates a sea breeze front which you can find more or less along the entire coast of britain in the summer.
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Post by poitsplace on Sept 21, 2009 20:42:39 GMT
You can't use a dehumidifier to remove the water vapor without screwing up the experiment. Over 25% of the entire energy budget of earth moves through the the troposphere every day as latent heat. This energy is what maintains the lapse rate in the troposphere. Its just the altitude it has to reach before it can finally reach a radiative balance from the top of water vapor's area of control.
Also the lapse rate doesn't exactly stop at the tropopause...it reverses but temperatures go up at a lower rate (I think about 1/6 the rate...could be wrong)
Since CO2 doesn't control the gradient, CO2 levels aren't going to change temperatures anywhere but the place CO2 has dominion...the tropopause. More absorption in the tropopause would just let more out. This of course assumes that CO2 is making that notch in earth's outgoing spectrum.
I'm guessing (could be wrong) if you shot a sample of high humidity air and CO2 with CO2's emission spectrum (or at least, with a laser that affected both water and CO2) you'd find that a huge amount of the energy would actually leave via water vapor's spectrum. Water vapor would be a big stumbling block for so-called "back radiation" since it would just keep the water vapor that's heading up from condensing and shift the troposphere up to compensate.
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Post by radiant on Sept 22, 2009 5:58:54 GMT
You can't use a dehumidifier to remove the water vapor without screwing up the experiment. Over 25% of the entire energy budget of earth moves through the the troposphere every day as latent heat. This energy is what maintains the lapse rate in the troposphere. Its just the altitude it has to reach before it can finally reach a radiative balance from the top of water vapor's area of control. Also the lapse rate doesn't exactly stop at the tropopause...it reverses but temperatures go up at a lower rate (I think about 1/6 the rate...could be wrong) Since CO2 doesn't control the gradient, CO2 levels aren't going to change temperatures anywhere but the place CO2 has dominion...the tropopause. More absorption in the tropopause would just let more out. This of course assumes that CO2 is making that notch in earth's outgoing spectrum. I'm guessing (could be wrong) if you shot a sample of high humidity air and CO2 with CO2's emission spectrum (or at least, with a laser that affected both water and CO2) you'd find that a huge amount of the energy would actually leave via water vapor's spectrum. Water vapor would be a big stumbling block for so-called "back radiation" since it would just keep the water vapor that's heading up from condensing and shift the troposphere up to compensate. I mentioned i think humidifiers but you are right you dont want to alter the dynamics of the system by adding heat from motors or whatever if that is what you meant? I think you can make a cooler that works by heating part of the coolant as in a gas fridge so maybe dehumidifiers could be used somehow? As i understand the water cycle water vapour being so light takes heat from the surface. Once it is in the atmosphere it must radiate some of this heat back to the surface. Then the whole mixture rises while cooling due to adiabatic expansion and then at the dew? point the water leaves the air and is cooled?and the air is warmed. The hot air then further fuels the impulse to take this air to great height and of course it still has some water with it. Eventually at great altitude the clouds evaporate or ice clouds form which must radiate whatever heat they have and the ice desends to lower altitudes because it is now a dense solid. So the water cools the earth but later warms the air and must be later cooling the air since it is so super cold with altitude. C02 must also be cooling the air. But also their emitted heat must be partly warming the surface Have you got a picture of one of these satellite images? To make sense of the images we need to see many images not some cherry picked one for some exceptional atmospheric condition. C02 must be doing something. what we know from the politics of this saga is that C02 is hyped as a toxic gas while water is minimised as the main greenhouse gas in a dishonest manner Even so C02 is doing something. That is the whole point of the thought experiment or actual experiment to show via a scientific method what the relative differences will be. I still think a simple experiment would reveal more than thousands of words and arguments would do Importantly agreeing on the experiment design also clarifies what we expect to find and what we dont know that we are hoping to find out.
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Post by steve on Sept 22, 2009 9:20:10 GMT
There is no ideal unmixed parcel of air or perfect thermal or anything else. Whether convection happens or not depends on whether there is a tendency for air to rise. That tendency will increase if the temperature profile of the atmosphere is steeper than the adiabatic lapse rate and will decrease if the profile is shallower (as in a temperature inversion).
If convection gets going (ie. if the temperature profile is steep), it shifts quite a lot of energy so will be effective in forcing the atmosphere to tend towards to the adiabatic lapse rate.
So when you say:
that may be true, but it *will* mix some of its energy, and it will only rise if the atmosphere is unstable - that is, its temperature profile is steeper than the adiabatic lapse rate. Otherwise where does it go? Does it rise till it reaches outer space and exist as a warm bubble on the top of the atmosphere?
The steeper the profile, the more convection and the more mixing. Because convection shfts a lot of energy it will be effective in changing the temperature profile to better conform to the lapse rate.
In fact, when I think about it, you are talking about advection (which is a more idealised process in which the heat content of a parcel is preserved) where as convection involves diffusion of heat through eddies created at the outskirts of the convective column.
Relating to radiation emission or lack of it:
If the atmosphere doesn't radiate much, it also doesn't absorb much. So it will be colder throughout. What I said earlier is that the lack of absorption/radiation may make other processes such as conduction more important. So, for example, warming and cooling at the surface may be proportionately higher than warming aloft because conduction from a sun-warmed/radiation cooled surface is relatively more important than radiation. But also, warming aloft due to absorption of UV by ozone may also be more important which could make the atmosphere more stable and might in this way suppress convection - ie. the N2/O2 atmosphere might tend towards a stable stratosphere like profile rather than an unstable troposphere like profile.
If convection remains unimportant, then there is little to couple the surface to the atmosphere. The surface will get hot during the day and cold during the night, but the atmosphere won't vary much and will be driven only by the the small amount of microwave it absorbs from the surface or by any UV energy it absorbs due to ozone etc.
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Post by poitsplace on Sept 22, 2009 10:19:01 GMT
But most of the earth is covered with water or at least fairly moist. More energy moves with water vapor and higher water vapor concentrations cause changes to the lapse rate that (as I've said numerous times) would tend to make the warming occur at the tropopause...reducing the amount of absorption at the only part of the atmosphere restricting CO2's wavelengths. en.wikipedia.org/wiki/File:795px-Emagram.gif...so CO2's affect on the lapse rate is going to be far lower than one would expect from the oversimplified, CO2 absorption math. Also, remember the CO2 can't move CO2's radiative zone UP to drag out the lapse rate over a greater distance because it's also warmer above the tropopause and that would also allow more energy out.
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Post by radiant on Sept 22, 2009 10:37:09 GMT
There is no ideal unmixed parcel of air or perfect thermal or anything else. Whether convection happens or not depends on whether there is a tendency for air to rise. That tendency will increase if the temperature profile of the atmosphere is steeper than the adiabatic lapse rate and will decrease if the profile is shallower (as in a temperature inversion). If convection gets going (ie. if the temperature profile is steep), it shifts quite a lot of energy so will be effective in forcing the atmosphere to tend towards to the adiabatic lapse rate. So when you say: that may be true, but it *will* mix some of its energy, and it will only rise if the atmosphere is unstable - that is, its temperature profile is steeper than the adiabatic lapse rate. Otherwise where does it go? Does it rise till it reaches outer space and exist as a warm bubble on the top of the atmosphere? The steeper the profile, the more convection and the more mixing. Because convection shfts a lot of energy it will be effective in changing the temperature profile to better conform to the lapse rate. In fact, when I think about it, you are talking about advection (which is a more idealised process in which the heat content of a parcel is preserved) where as convection involves diffusion of heat through eddies created at the outskirts of the convective column. Relating to radiation emission or lack of it: If the atmosphere doesn't radiate much, it also doesn't absorb much. So it will be colder throughout. What I said earlier is that the lack of absorption/radiation may make other processes such as conduction more important. So, for example, warming and cooling at the surface may be proportionately higher than warming aloft because conduction from a sun-warmed/radiation cooled surface is relatively more important than radiation. But also, warming aloft due to absorption of UV by ozone may also be more important which could make the atmosphere more stable and might in this way suppress convection - ie. the N2/O2 atmosphere might tend towards a stable stratosphere like profile rather than an unstable troposphere like profile. If convection remains unimportant, then there is little to couple the surface to the atmosphere. The surface will get hot during the day and cold during the night, but the atmosphere won't vary much and will be driven only by the the small amount of microwave it absorbs from the surface or by any UV energy it absorbs due to ozone etc. We need to agree basic terms and recognise some basic atmospheric physics A typical people carrying hot air ballon contains 3.4 tonnes of air. Once that small volume gets moving it does not matter if it heavier or lighter than air, because it just wants to keep on moving considerable distances thru different densities of air because it has the momentum of 3.4 tonnes The adiabatic lapse rate is the rate of temperature fall as a parcel of air moves upwards in the atmosphere So a parcel of air moving upwards cools at various adiabatic lapse rates depending upon the moisture content of the parcel of the air But the parcel of air beginning at the earths surface is surrounded by air that descends in temperature as you go higher which is called the lapse rate The parcel of air does not mix significantly with the surrounding air while it is rising and expanding if it is sufficiently large because of the momentum of the molecules. only the outer edge of the bubble can be influenced. Of course there is mixing but the idea is that if the bubble rises it cannot be significant. If it is significant it stop rising and becomes part of the surrounding air. And we know from everyday experience that such bubbles do rise and form cumulus clouds. Go visit a gliding club if you doubt this. Yes the air cannot be stable and be capped by a hotter layer or air that is descending to prevent thermals forming. 50% of the time in summer thermals are forming i would say from my own gliding experiences. The warm moist air on the surface is rapidly moved to a few thousand feet or more at rates around 100 to 400 feet per minute typically Similarly to a thermal a much huger high pressure area is a totally different mass of air to a low pressure area and can only be influenced or destroyed at the boundary where the air mixes and collides and veers. The outer layers do not act upon the inner layers which have entirely different momentum and forces. So air that expands as a parcel thru the surrounding air has an adiabatic lapse rate It cools at a certain rate depending upon its moisture content that is not related to the moisture content and temperature of the air it is surrounded by. It is like a balloon going upwards in cooler air. Regardless of the lapse rate of the surrounding air if the parcel is lighter than this air it ascends thru the surrounding air while it cools at the adiabatic lapse rate Strong thermal activity can take such parcels 48,000 feet into the air. An aircraft can fly around such a parcel and not encounter turbulence but be destroyed if it flies thru it. Why are you insisting on using the wrong term?? Why are you denying the common experience and knowledge of other people who have flown thru, rose upwards thru, and examined these phenonema? Advection appears to be when cooler air is taken higher by the action of a rising thermal or when rain that is falling in a rain cloud is taken higher by the intensity of the heat flows circulating in the clouds so these flow can take the rain so high it can freeze and then descend as hail. Google mentions orographic cloud as associated with advection I never heard the term advection but orographic clouds are wave clouds where air rising over mountains or smaller hills near the sea takes with it the moisture of the air to form clouds very high in the atmosphere Advection and convection where the atmosphere is moist can amount to the same thing it seems to me because the air rises and part of the reason the air rises is the high water vapour content means the air is not just warm but also light because water vapour is such a light gas. Therefore advected slightly warm air at the surface that is not sufficiently warm to rise without water vapour does rise with water vapour and in turn become part of the momentum and forces taking the cloud higher thru the surrounding cooler lower pressure air If the atmosphere doesn't radiate much, it also doesn't absorb much. So it will be colder throughout. It has nothing to do with absorption. The air contacts the hot surface of the air and then rises The air touching the cold surface of the earth just stays at the surface and then this cold air layer contacts the next layer of warmer air just above the surface and cools that. The warmer air above is insulated by the temperature gradient thru the air But hot air rises. So heat preferentially will move into the atmosphere and preferentially will not come out of it unless it can get to the absolute surface of be in contact with air that has been in contact with the absolute surface
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Post by radiant on Sept 22, 2009 10:55:53 GMT
But most of the earth is covered with water or at least fairly moist. More energy moves with water vapor and higher water vapor concentrations cause changes to the lapse rate that (as I've said numerous times) would tend to make the warming occur at the tropopause...reducing the amount of absorption at the only part of the atmosphere restricting CO2's wavelengths. ...so CO2's affect on the lapse rate is going to be far lower than one would expect from the oversimplified, CO2 absorption math. Also, remember the CO2 can't move CO2's radiative zone UP to drag out the lapse rate over a greater distance because it's also warmer above the tropopause and that would also allow more energy out. I cant follow what you are saying. Do you have some links to this stuff i could try and work thru please?
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