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Post by kiwistonewall on Oct 13, 2009 22:18:42 GMT
Steve, you are almost totally incorrect. My advice is to study thermodynamics, physical chemistry & get you head around it all. Since the narrow spectral bands are due to (at IR energies) rotational and vibrational changes in polyatomic moelcules (e.g. water and CO2) these are entirely different from THERMAL processes (related to the speed of molecules and the boltzmann Distribution. These narrow spectra are optically BLACK, (which means, incidentally, that they are saturated, but I dont intend to go there!) while the rest of the gases are optically grey. The bulk of the thermal IR band (from Earth's longwave radiation) is going to interact with the WHOLE atmoipshere. In the total absence of green house gases we would still have a substantial greenhouse effect. Oxygen and nitrogen (and Argon etc) DO emit & absorb quite well at the predicted thermal energies. Spectral lines from H2O etc, do not obey the T^4 laws, and are an entirely different process. All this is well established and well understood in all scientific circles except in the propaganda adapted for the scientifically illiterate.
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Post by steve on Oct 13, 2009 22:33:21 GMT
Steve, you are almost totally incorrect. My advice is to study thermodynamics, physical chemistry & get you head around it all. Since the narrow spectral bands are due to (at IR energies) rotational and vibrational changes in polyatomic moelcules (e.g. water and CO2) these are entirely different from THERMAL processes (related to the speed of molecules and the boltzmann Distribution. These narrow spectra are optically BLACK, (which means, incidentally, that they are saturated, but I dont intend to go there!) while the rest of the gases are optically grey. The bulk of the thermal IR band (from Earth's longwave radiation) is going to interact with the WHOLE atmoipshere. In the total absence of green house gases we would still have a substantial greenhouse effect. Oxygen and nitrogen (and Argon etc) DO emit & absorb quite well at the predicted thermal energies. Spectral lines from H2O etc, do not obey the T^4 laws, and are an entirely different process. All this is well established and well understood in all scientific circles except in the propaganda adapted for the scientifically illiterate. Kiwistonewall, You have almost totally misunderstood. The molecules both emit and absorb energy. To emit energy, the molecules must be excited to a vibrational/rotational whatever state. Almost all the excitation is done by collision rather than by absorption at atmospheric temperatures and pressure. As a result, the proportion of excited photons is *dependent* on the thermal distribution. Because of the pressure and temperature, the spectral lines are broadened (look up "pressure broadening" for example). Also You don't make it clear what you mean by saturation, and it sounds like you have it a bit confused. If all the photons at a particular frequency from the surface of the earth are absorbed, that could be described as "saturation". But the gases doing the absorption also *emit* at the same frequency, so you do not get "black" lines if you are measuring the emission spectrum of the atmosphere from, for example, a satellite. You get black lines when you have a much hotter gas behind a cooler gas and are looking from a distance. Here the cool gas absorbs the photons from the hot gas at certain frequencies, but because the subsequent emission is diffuse (so most of the emission is not towards you), you get a black line. Eg. when you look at the solar spectrum. PS. I have studied thermodynamics and physical chemistry to a reasonable level. It's a bit rusty now, but good enough to deal with this issue.
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Post by radiant on Oct 13, 2009 23:07:01 GMT
Radiant, The winds are caused by low pressure systems...Read the simple explanation from the first link. meteora.ucsd.edu/cap/santa_ana.html#circulation
What atmospheric circulation features are associated with Santa Ana events?
Any low-pressure system in the Pacific off the California coast may change the stability of the Great Basin High. The Great Basin High winds then turn southward along the eastern slopes of the Sierras. The low-pressure system over the Pacific literally sucks the winds through the mountain passes of Southern California toward the coastal areas.Kinda like a ball sitting on a hill v/s rolling down hill. If nothing touches it, it will stay there. Once something starts it. It accelerates as it goes down hill. The point was just to fill in the gap about your knowledge of Santa Ana winds. You said in your post above were I initially posted that you weren't sure about them. Stanb999 Your point was to tell me i was wrong Wiki is not the best source It really has noting to do with the affect you note.Now you are telling me what Wiki tells me but Wiki seems more accurate to me.
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Post by radiant on Oct 13, 2009 23:50:00 GMT
I agree with much (not all) of what radiant says. The givens are: 1. ALL substances emit and absorb thermal energy (also called blackbody radiation) - this is a fundamental property of matter. The first bit is true. But blackbody radiation is radiation from an idealised "black body". Probably only black holes emit black body radiation. True. But they are both a function of wavelength. They are high at the wavelengths of the spectral lines of the material and low in between the spectral lines of the material. Sentence 2 in this has confused "thermal energy" which is a function of the velocities of the atoms and molecules when they have reached local thermal equilibrium, with emittance and absorption (did you mean absorptivity) which are functions of wavelength. Although, absorption is largely independent of temperature and is a function of absorptivity (which is a function of wavelength). The amount of emission depends on how often collisional excitation followed by molecular emission occurs. Emission only happens at spectral lines, though lines can be quite broad at atmospheric temperatures and pressures. Because total emission depends on how often excitation+molecular emission occurs, and because this depends on the velocities of the molecules, and because the velocities have a thermal distribution, the spectral lines tend to line up with the black body curve. They do not line up with the black body curve by Planck magic. For the above reasons, it might look this way when the spectral lines are broad (at higher temperatures and pressures), but spectroscopy of the air shows up broad lines from water vapour, and spectroscopy of hot interstellar gas shows up more discrete emission lines. Indeed! The first sentence is faulty. Spectral lines are the collective result of emission from many excited molecule. The processes that excite the molecules influence the shape of the spectrum. If the molecules are excited by thermal processes, the spectrum will align with the black body curve. If the gas is irradiated by the jet from a galactic centre black hole, then the spectral lines will depend on the energy of the (possibly non-thermal) radiation and will follow a different shape. I am tending to agree with most but not all of what Steve says Tyndall showed that all of the IR from the oxy hydrogen flame at 5898F which produces water in the flame, was entirely absorbed by only 0.27inches of water at 60F. Further he said that 96.7% of the IR from the flame is absorbed by only 0.04inch of water. Tyndall said that temperature increased amplitude but did not influence the rate of vibration Obviously there is no detectable Ir coming out of that hot gaseous flame that a very small amount of water or water vapour cannot absorb so the flame cannot possibly be a black body radiator even when at enormous temperature Further Kiwis own links tell us that N2 and 02 are undetectable by any IR method By what method is it well known to science that N2 is a black body emitter in the IR band when you cannot detect the emission by any method known to science?? Further why are we supposedly influenced by climate change propaganda when one of the finest scientists ever to live thinks in 1860 that n2 and 02 are like a vacuum to IR and in fact he found that ordinary o2 has more absorption from ozone than could be detected in the ordinary oxygen??
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Post by icefisher on Oct 14, 2009 3:08:34 GMT
Further why are we supposedly influenced by climate change propaganda when one of the finest scientists ever to live thinks in 1860 that n2 and 02 are like a vacuum to IR and in fact he found that ordinary o2 has more absorption from ozone than could be detected in the ordinary oxygen?? I would throw the practicality card on that play. Scientists are focused on practical applications of the day and O2 and N2 had no practical IR capabilities in the context of 1860. Financial markets run with the same blindfolds. When money is moving and its being made the focus narrows to the here and now and recent practical experience. . . .people just don't think about paradigm shifts and the sudden applicability of massive shifts in financial climates. Only since the creation of major populations in the idle class has science tracked so far to the impractical. They think every immediate lifetime need of mine has triple warranties and insurances and all I have to worry about is the end of the world. . . .and they do.
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Post by kiwistonewall on Oct 14, 2009 3:51:51 GMT
As usual, Radiant misses the point when he says: "Further Kiwis own links tell us that N2 and 02 are undetectable by any IR method"
I was pointing out the difficulty of separating O2 & N2 radiation from background thermal radiation without the use of cryoscopic equipment. The back radiation from space does indeed contain the entire BB spectrum from O2 & N2 & Ar, along with spectral peaks, but needs cryoscopically cooled sensors to differentiate from the equipment itself.
But to say that because something cannot be easily detected when we KNOW it is there is simple being an Ostrich. It is there, and IS detectable, but we have no pure O2 & N2 atmosphere handy to prove this to the simple minded.
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Post by radiant on Oct 14, 2009 5:36:09 GMT
As usual, Radiant misses the point when he says: "Further Kiwis own links tell us that N2 and 02 are undetectable by any IR method" I was pointing out the difficulty of separating O2 & N2 radiation from background thermal radiation without the use of cryoscopic equipment. The back radiation from space does indeed contain the entire BB spectrum from O2 & N2 & Ar, along with spectral peaks, but needs cryoscopically cooled sensors to differentiate from the equipment itself. No! You provided details of Hammers study! AN ANALYSIS OF THE EFFECT OF GREENHOUSE GASES IN THE ATMOSPHERE By Michael Hammer
Greenhouse gases in the atmosphere act entirely through radiative processes.
5. THE SIGNIFICANCE OF EMISSIVITY
Most of the atmosphere is made up of nitrogen and oxygen which do not significantly absorb infrared energy because their emissivity in this portion of the electromagnetic spectrum is exceptionally low. This means they also do not emit significant infrared – they are not greenhouse gases. Other gases however have a very strong ability to absorb energySo you provide a link to a study and now you want to tell everybody the study author is simple minded! But to say that because something cannot be easily detected when we KNOW it is there is simple being an Ostrich. It is there, and IS detectable, but we have no pure O2 & N2 atmosphere handy to prove this to the simple minded. You need to buy a mirror and take a good long hard look at your own lack of objectivity before you continually abuse others who can see you are not making any sense with these links that do not support your own point of view What motivates somebody to say: All matter emits radiation based on its temperature. You must have skipped those lectures. I am not in the least interested in debating with you. I was just pointing out the common ignorance about radiation & correcting the assertion that O2 & N2 do not absorb & emit thermal radiation. And then provide a link which says the exact opposite?? Most of the atmosphere is made up of nitrogen and oxygen which do not significantly absorb infrared energy because their emissivity in this portion of the electromagnetic spectrum is exceptionally low. This means they also do not emit significant infrared – they are not greenhouse gases. Other gases however have a very strong ability to absorb energy
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Post by northsphinx on Oct 14, 2009 7:01:55 GMT
An atmosphere of only nitrogen and oxygen will have a strong Greenhouse effect. The sun will heat the earth surface and the surface will heat the atmosphere by heat transfer. The surface will be cooled by wind that heats the atmosphere. Warmer air will rise. The whole atmosphere will be heated. But during the night when radiation cool the earth surface will the cooling of the atmosphere be less efficient than heating. That is because the hot air will not loose energy by radiation and will not sink to the cold surface.
It is impossible to cool the entire atmosphere from the bottom of it without clouds and radiation.
The result will be a warmer atmosphere than the average temperature the radiation balance calculation for the surface would show.
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Post by radiant on Oct 14, 2009 7:16:48 GMT
An atmosphere of only nitrogen and oxygen will have a strong Greenhouse effect. The sun will heat the earth surface and the surface will heat the atmosphere by heat transfer. The surface will be cooled by wind that heats the atmosphere. Warmer air will rise. The whole atmosphere will be heated. But during the night when radiation cool the earth surface will the cooling of the atmosphere be less efficient than heating. That is because the hot air will not loose energy by radiation and will not sink to the cold surface. It is impossible to cool the entire atmosphere from the bottom of it without clouds and radiation. The result will be a warmer atmosphere than the average temperature the radiation balance calculation for the surface would show. I agree with you but this is not what is meant by greenhouse effect as it applies in todays terminology By the way are you able to calculate radiation balances? Importantly since most of the earth is covered in water which cools via waters emissions most of the radiation emitted by the cooling earth is relatively transparant to many other absorbers. If the calculations assume black body emission from the earth then they will get a cooler earth. Modis data for water and ice looks like this and uses low resolution spectrometers. In reality there is no graph line and instead it is many tiny spikes with gaps. But i must admit that i am confused by the difference sources i am reading! People like Tyndall did painstaking experimental work whereas modis is produced in some kind of other way. Are you able to do such a calculation? One of kiwis links said that the emissivity of water was about 0.5 most links say it is over .95 Tyndall observed the emissivity of the hydrogen flame in its ability to radiate heat as being poor for such a very hot flame and that flame is only emitting waters radiation So something does not add up here!
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Post by steve on Oct 14, 2009 8:39:48 GMT
An atmosphere of only nitrogen and oxygen will have a strong Greenhouse effect. The sun will heat the earth surface and the surface will heat the atmosphere by heat transfer. The surface will be cooled by wind that heats the atmosphere. Warmer air will rise. The whole atmosphere will be heated. But during the night when radiation cool the earth surface will the cooling of the atmosphere be less efficient than heating. That is because the hot air will not loose energy by radiation and will not sink to the cold surface. It is impossible to cool the entire atmosphere from the bottom of it without clouds and radiation. The result will be a warmer atmosphere than the average temperature the radiation balance calculation for the surface would show. I'm on radiant's side in his discussions with Kiwistonewall. With the above though, what has been ignored is the effectiveness or otherwise of the "heat transfer" to the atmosphere. Much of the heat transfer from the surface to the atmosphere is done by radiative heating. The ground radiates, and much of the radiation is absorbed by the atmosphere near the surface by, principally, water vapour, but also by CO2, CH4 etc. If there were no greenhouse gases (by which I mean gases that absorb significantly in the wavebands emitted by the earth's surface) then the radiation emitted by the earth will escape to space. That is what cools the earth. Oxygen emits and absorbs at 60Hz, but the earth doesn't emit much at this waveband, so the oxygen has little effect. Furthermore, because of the lack of greenhouse gases, the surface will not warm as much - it could be on average about 30C less (although the diurnal cycle will be more extreme). This is a simple application of the Stephan-Boltzmann equation to an object in equilibrium at the distance of 93 million miles from the Sun. To make this more explicit, both the earth *and* Venus are, on the outside (ie. the upper part of the atmosphere that radiates heat into space) about the same temperature of 250 Kelvin. The reason why Venus is not much warmer despite being close to the Sun is because its clouds are brighter which means it reflects away more of the sunlight and absorbs only about as much as the earth.
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Post by icefisher on Oct 14, 2009 9:40:39 GMT
Most of the atmosphere is made up of nitrogen and oxygen which do not significantly absorb infrared energy because their emissivity in this portion of the electromagnetic spectrum is exceptionally low. This means they also do not emit significant infrared – they are not greenhouse gases. Other gases however have a very strong ability to absorb energy Radiant you have latched onto an untested premise in Hammer's study. Actually I don't think its even relevant to Hammer's study except to attribute almost all radiation to space from the surface as opposed from the warm areas of the lower atmosphere. Even if insignificant is wrong, it probably doesn't matter to the Hammer theory. Kiwi's stuff seems compatible with Hammer, its just not something Hammer considers. Anyway Hammer doesn't say zero he says not "significant". But again in the world of practically this issue doesn't matter because nobody is coming close to changing the larger composition of the atmosphere (e.g. 99% of it). Ultimately it seems what Hammer is saying is there is no energy being emitted from the area of the atmosphere dominated by CO2 as its too cold there. So its also reasonable to conclude it is also too cold for the O2 and N2 in the same region also. An aside on Hammer, it seems a pretty good theory that the radiation has to be taking a different path or the warmer stratosphere would be warming the upper tropopause via radiation exchange but it fails to do so because the heat is escaping to space from that region in some kind of equillibrium in the co2 bands down to maybe an average of 15,000 feet if i am understanding hammer correctly.
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Post by glc on Oct 14, 2009 10:35:08 GMT
Ultimately it seems what Hammer is saying is there is no energy being emitted from the area of the atmosphere dominated by CO2 as its too cold there.
So what is the "CO2 funnel" that shows up in earth's emission spectra all about then?
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Post by icefisher on Oct 14, 2009 15:15:30 GMT
Ultimately it seems what Hammer is saying is there is no energy being emitted from the area of the atmosphere dominated by CO2 as its too cold there.So what is the "CO2 funnel" that shows up in earth's emission spectra all about then? Its an absence of emissions.
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Post by steve on Oct 14, 2009 15:24:04 GMT
Ultimately it seems what Hammer is saying is there is no energy being emitted from the area of the atmosphere dominated by CO2 as its too cold there.So what is the "CO2 funnel" that shows up in earth's emission spectra all about then? Its an absence of emissions. Oh dear! I suggest you revise Kirchoff's theorem. If it is absorbing it must also be emitting. Otherwise it will get steadily "hotter" and "hotter". (hotter is in quotes because it is describing a physically impossible scenario).
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Post by icefisher on Oct 14, 2009 16:13:36 GMT
Ultimately it seems what Hammer is saying is there is no energy being emitted from the area of the atmosphere dominated by CO2 as its too cold there.So what is the "CO2 funnel" that shows up in earth's emission spectra all about then? Its an absence of emissions at those frequencies.
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