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Post by radiant on Oct 13, 2009 2:04:37 GMT
Question for radiant: In one of your posts you said air is heated by contact with the surface? If the earth is 7/10ths ocean and only 3/10th land ... I guess I'm confused. I thought the oceans were absorbing all that heat. How much of the air can possibly be heated by contact with the surface? So the water in a pool gets heated by magic? I always thought the sun heated it. My actual question is " what kind of evidence will it take to admit that co2 is not the dominant player in atmospheric warming?" From what I can tell co2 is a lagging indicator, and not a leading. It would be interesting to see if there isn't a flip flop and say that an increase in co2 is usually before a dramatic drop in temps and that should be the reason for banning co2. The AWG crowd remains me of the logic in the old Soviet Union. The real evidence, however, won't go away. You can spin a story only so far. When a nuclear plant catches on fires and spreads radiation all over, it's hard to explain that away. We've had colder weather when the sun was quiet and warmer when it was active. That is not going away. Hooting and hollering about co2 being the main cause of warming when the sun was very active looks like poor science ( well it is poor science ). In fact, the sun had longer periods of being active since the fifties were there were double peaks in sunspot activity. I wasn't surprised that temps were warmer, and I won't be surprised when temps fall when the sun turns quiet. What will happen to your credibility when that happens? Will that be your legacy? Spaceman You are confused here. But the topic is confusing. I am not saying C02 is a major player in atmospheric warming Perhaps you can therefore rephrase your questions and assumptions and start again please.
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Post by radiant on Oct 13, 2009 2:52:14 GMT
My comments in yellowThe givens are: 1. ALL substances emit and absorb thermal energy (also called blackbody radiation) - this is a fundamental property of matter. Blackbody radiation is an idealised theoretical concept
John Tyndall knew in 1860 that gold and silver were very poor emitters of radiation compared to varnish.
books.google.com/books?id=35c5AAAAcAAJ&pg=PA290#v=onepage&q=gold&f=false
Blackbody radiation is a useful idea
2. Emittance and absorptivity are two sides of the same equation. (This is a fundamental thermodynamic fact) I think i agree with your wording. What absorbs emitts equally. What does not absorb will not emit. 3. Thermal energy is a result of molecular and atomic motion, and has ZERO, ZIP, ZILCH to do with absorption spectra. Thermal energy is emittance and absorption over a continuous range of frequencies, whereas spectra are discrete lines at specific frequencies. John Tyndall in 1860 knew that H2 N2 02 were 'like a vacuum to the absorption of heat'. And he knew this was related to molecular properties and vibrations.
books.google.com/books?id=35c5AAAAcAAJ&printsec=frontcover&source=gbs_v2_summary_r&cad=0#v=onepage&q=gold&f=false
Heat considered as a mode of motion
Note that diathermacy is transparancy and athermacy is opacity. IR radiation was an 'obscure' calorific ray. 4. Gases emit an almost perfect thermal (blackbody) curve, but their emissivity (absorptivity) is less than 1, and they are therefore termed "grey bodies" Tyndall showed this was not true.5. There is a huge amount of confusion amongst those who don't understand, and who rely on authorities that also don't understand. (This also is an obvious fundamental truth!!) Are you saying that John Tyndall was wrong?5. Spectral lines can be extremely intense, and are a completely different process to thermal radiation, and an order of magnitude (or more) stronger than thermal. Hence, when comparing spectral lines with background radiation, it is entirely true to refer to gases which do not have spectral lines as "not absorbing" IR, but that is only true in the context of spectroscopy, and is a huge oversimplification. Tyndall knew that the heat of the flame of pure oxygen and hydrogen was entirely due to the characteristic diagnostic emittance from the vibrations of water.
Tyndall knew that that the heat of the flame of Carbonic oxide was entirely due to the characteristic diagnostic emittance from the vibrations of C02 which was at that time called carbonic acid.
Tyndall knew that the heat from a filament of white hot platinum contained a continuous spectrum whereas when the filament was even hotter and vapourising the spectra contained areas of black related to the absorption of platinum.
We are in the suns atmosphere and we observe the sun via its photosphere and we see the absorption of the components of the photosphere. Tyndall knew that.
What is really meant is that oxygen and Nitrogen do not have any visible absorption over the background thermal radiation - but they participate in that background thermal radiation and emit & absorb like every other substance. Nothing is meant by 'n2 and 02 do not emitt ir radiation other than what it says. 6. It is extremely difficult to measure background thermal radiation due to the fact that EVERYTHING is radiating thermal energy, whereas spectral lines stand out like a sore thumb. To measure the effect from O2 & N2, we would need a cryogenic tube several kms long filled with dry O2 & N2 at a warmer temperature (minus GHGases), with cryogenic measuring equipment at one end, and an ideal BB radiator at whatever temperature we wanted at the other. The gas in the tube, (in contact with the cryogenic surface, would also need to be warmed to the correct temperature.) Such an apparatus is next to impossible to create! We can agree that IR radiation from gases is very slight. In the case of our atmosphere IR radiation from the atmosphere acts to cool the relatively trivial atmospheric mass and effectively does not warm the earth but rather acts to prevent cooling of the earth since the earth cannot see the coldness of space7. At the top of the atmosphere, the IR thermal radiation can be measured from the Earth. But we cannot tell how much of that thermal radiation has been absorbed & re-emitted by the intervening gas - the reason is that the thermal curves have the same shape!! Only the GHG can be seen in their narrow spectra. Thus, the greenhouse effect of Oxygen and Nitrogen cannot be directly measured. Really we are talking at crossed purposes. N2 is warmed by the earths surface but cannot cool unless water cools it or it descends to the cold earths surface8. 99.964% of the DRY Atmosphere is made up of non GH gases (mainly O2, N2 and Argon). Seems ok to me9. The thermal power is the Area under the thermal curve, of which the area under the spectral lines of CO2 and CH4 is very small. No comment. Nothing to say about this.10. Apart from water and clouds, the bulk of the IR optical density in the atmosphere is caused by non Greenhouse gases. This has been estimated at around 65%. (debatable) The other 35% is caused by the GH gases, nearly all water. The GH gases do indeed have a major contribution to the overall optical density. As we move across the thermal band for a particular temperature, there will be a grey optical depth over most of the band, with narrow optically black lines where molecules have absorption spectra. When temperature changes, the band moves, but the spectral lines do not. Thus, IF the narrow bands caused nearly all the thermal absorption, the emissivity would extremely sensitive to temperature. The paper I linked in the first post in this thread shows that it is not. Ergo, the bulk of the greenhouse effect is caused by non-greenhouse gases, which was long recognized until the population needed to be re-educated! Again i have to ask you. Are you saying that Tyndall was wrong? I think it would be easier if you show me where you think Tyndall was wrong. You need to consider Tyndalls simple experiments: books.google.com/books?id=35c5AAAAcAAJ&pg=PA430#v=onepage&f=falseIf you burn very purified oxygen and hydrogen the colourless flame at 5898 Fahrenheit is only producing the characteristic diagnostic emissions of water. And yet there is a body of gas there. You keep saying it is a black body. On the one hand there is a theory of black body radiation. Then there is the practice and the experiments. Tyndall found his 5898F hydrogen oxygen flame produced no detectable ray that could be absorbed by dry air without C02 and yet which easily absorbed rays when ordinary atmospheric air was present. He reasoned the only difference between the vibrational states of the water in the flame at 5898F and the water in his test cylinder at 60F was one of amplitude rather than rate of vibration. Tyndall showed that when the oceans are cooling or the moist layer of water on the surface of the earth is cooling as it does each night, that the radiated heat from water is entirely absorbed in 0.27 inches of water - a tiny amount of water easily found just above the surfaces of the earth in nearly all warm locations. Further he showed that just 0.04 inches of water was sufficient to absorb 96.8% of the heat of a hydrogen flame. This means that the emitted heat from atmospheric water is sufficient to prevent the oceans from seeing the full cold of space even when present in small quantities. Further he was able to show that even when water is rare in the atmosphere, water preferentially absorbs very strongly the radiation from water whereas other substances do not. Modern studies show that even in Antarctica where there is almost no water in the entire atmosphere above Antarctica that most of the skys temperature comes from water in the atmosphere.
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Post by kiwistonewall on Oct 13, 2009 8:19:07 GMT
Dear Radiant, did you always argue with your teachers? Truth is not in the number of posts.
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Post by radiant on Oct 13, 2009 9:02:56 GMT
Dear Radiant, did you always argue with your teachers? Truth is not in the number of posts. Kiwi If you want to believe that John Tyndall was wrong then you are welcome to hold such a belief He should be your teacher in this i believe and he lived long before any of your teachers or mine. Tyndall was the successor to Michael Faraday at the Royal Society en.wikipedia.org/wiki/John_TyndallYour teachers message is: A point of very considerable importance forces itself upon our attention here, namely the vast practical differences that may exist between the two phrases, 'obscure rays' and 'rays from an obscure source'. Many writers seem to regard these two phrases as equivalent to each other and are thus led into grave errors en.wikipedia.org/wiki/File:TyndallsSetupForMeasuringRadiantHeatAbsorptionByGases_annotated.jpg
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Post by steve on Oct 13, 2009 12:31:02 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.
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Post by stanb999 on Oct 13, 2009 13:36:28 GMT
I am not sure where you are going with the moist catabatic winds. Another factor is that air with water vapour is less dense and rises. If the water vapour precipitates then the dryer denser air wants to descend relative to the more moist air around it. By some process i cant understand yet the Santa Anna high desert air obtains a lower relative humidity as it descends - possibily the more humid air rises and causes the dryer air to descend in a continual process after the initial creation of high pressure in the upper valleys. My point about catabatic winds was more of an observation of something that happens in greenland and antarctica rather than it being any more than that. Dry surface air in Antartica is much more cold than air 200-300 metres higher, and since it is known that water in the air is associated with more radiation and dry air is associated with less radiation, there must be some kind of event happening there and i wanted to see if i could understand it. It made sense to me. Cooler (denser) drier (denser) heavy air moves down slope. Warmer and probably moister air replaces it. Santa Anna winds dry on the way up there and on the way down from wiki. I am doing my best to be helpful to you and you are telling me i am dancing and avoiding something Radiant, the Santa Ana winds are caused by warmer wetter air from the gulf sliding over the mountains, then descending again. It really has noting to do with the affect you note. It's driven by large movements of air masses and the jet stream. So the initial force of the wind isn't created by the mountains as in your example of Greenland. In your example. cold high air moves down slope without regard for the larger atmospheric circulations. Yours is a quite extreme example. A simpler to demonstrate example is frost forms in the valley.
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Post by radiant on Oct 13, 2009 13:56:46 GMT
I am not sure where you are going with the moist catabatic winds. Another factor is that air with water vapour is less dense and rises. If the water vapour precipitates then the dryer denser air wants to descend relative to the more moist air around it. By some process i cant understand yet the Santa Anna high desert air obtains a lower relative humidity as it descends - possibily the more humid air rises and causes the dryer air to descend in a continual process after the initial creation of high pressure in the upper valleys. My point about catabatic winds was more of an observation of something that happens in greenland and antarctica rather than it being any more than that. Dry surface air in Antartica is much more cold than air 200-300 metres higher, and since it is known that water in the air is associated with more radiation and dry air is associated with less radiation, there must be some kind of event happening there and i wanted to see if i could understand it. It made sense to me. Cooler (denser) drier (denser) heavy air moves down slope. Warmer and probably moister air replaces it. Santa Anna winds dry on the way up there and on the way down from wiki. I am doing my best to be helpful to you and you are telling me i am dancing and avoiding something Radiant, the Santa Ana winds are caused by warmer wetter air from the gulf sliding over the mountains, then descending again. It really has noting to do with the affect you note. It's driven by large movements of air masses and the jet stream. So the initial force of the wind isn't created by the mountains as in your example of Greenland. In your example. cold high air moves down slope without regard for the larger atmospheric circulations. Yours is a quite extreme example. A simpler to demonstrate example is frost forms in the valley. Stanb99 You could be right for all i know but you are in conflict with other sources including for example wiki. en.wikipedia.org/wiki/Santa_Ana_windsThe Santa Ana winds do not originate in precipitation, but in the bone-dry high deserts.The sources are saying the force of the Santa wind comes from the fact the air is cooled in the high desert and then via gravitational force then crashes back towards the lower levels Wiki also says: Winds blowing off the elevated glaciated plateaus of Greenland and Antarctica experience the most extreme form of katabatic wind, of which the Santa Ana is a type, for the most part. The winds start at a high elevation and flow outward and downslope, attaining hurricane gusts in valleys, along the shore, and even out to sea. Like the Santa Ana, these winds also heat up by compression and lose humidity, but since they start out so extraordinarily cold and dry and blow over snow and ice all the way to the sea, the perceived difference is negligible.
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Post by steve on Oct 13, 2009 14:47:59 GMT
I am not sure where you are going with the moist catabatic winds. Another factor is that air with water vapour is less dense and rises. If the water vapour precipitates then the dryer denser air wants to descend relative to the more moist air around it. By some process i cant understand yet the Santa Anna high desert air obtains a lower relative humidity as it descends - possibily the more humid air rises and causes the dryer air to descend in a continual process after the initial creation of high pressure in the upper valleys. (my bold) Radiant it is *THERE* in the Wikipedia article you referenced. The reduction in relative humidity is due to increase in temperature due to "adiabatic heating". The air contains the same amount of moisture, but "relative humidity" is a measure of humidity relative to the maximum amount of water vapour that can be held by air of that temperature. As the temperature rises due to the "adiabatic heating" the amount of water it *can* hold rises. Therefore the relative humidity decreases. The descent and ascent of air has almost nothing to do with the relative density of dry and moist air. Typical air might be 1% water by mass (10g per kilo). The volume of this water is approximately 28/18 times the volume of 10g of Nitrogen, so the relative density between the unlikely extremes of completely dry air and normal air is roughly 0.5% different.
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Post by radiant on Oct 13, 2009 15:50:21 GMT
I am not sure where you are going with the moist catabatic winds. Another factor is that air with water vapour is less dense and rises. If the water vapour precipitates then the dryer denser air wants to descend relative to the more moist air around it. By some process i cant understand yet the Santa Anna high desert air obtains a lower relative humidity as it descends - possibily the more humid air rises and causes the dryer air to descend in a continual process after the initial creation of high pressure in the upper valleys. (my bold) Radiant it is *THERE* in the Wikipedia article you referenced. The reduction in relative humidity is due to increase in temperature due to "adiabatic heating". The air contains the same amount of moisture, but "relative humidity" is a measure of humidity relative to the maximum amount of water vapour that can be held by air of that temperature. As the temperature rises due to the "adiabatic heating" the amount of water it *can* hold rises. Therefore the relative humidity decreases. The descent and ascent of air has almost nothing to do with the relative density of dry and moist air. Typical air might be 1% water by mass (10g per kilo). The volume of this water is approximately 28/18 times the volume of 10g of Nitrogen, so the relative density between the unlikely extremes of completely dry air and normal air is roughly 0.5% different. I agree I got confused that the santa ana wind is further dried as it descends whereas as you point out as it descends it has the ability to be more drying of the objects it passes by. The way to look at water vapour in air is to consider water vapour as a separate gas that enters the area above the surface of the earth. When damp areas are warmed at the surface they contain very high humidity. It is incorrect to say that water is in the air. Instead water is a separate gas and enters the air in concentration and then overall forms a certain percentage of the total air. en.wikipedia.org/wiki/PsychrometricsNote: the notion that air "holds" moisture, or that moisture dissolves in dry air and saturates the solution at some proportion, is an erroneous (albeit widespread) concept (see relative humidity for further details). As far as i recall a mole of water of 18 grammes occupies the same volume as a mole of nitrogen of 28 grammes. I dont think you can say this is an insignificant influence to add to the rising of warmed humid air and the descent of cold dry air. If you heat air it rises How about you do the maths and see how much lighter a volume of gas at 15 degree when heated 5 degrees and then compare it to the lightness of various volumes of air and water and then decide if it can rise or not? As far as i can tell the volume of the gas increases by 5/273 or 1.83% whether it is wet or dry so your 0.5% dry to normal ratio when warm humid rising air is not normal air means that it would be very significant. At atmospheric pressure, water when warm likes to form water vapour which rises in columns of moist air where the moist ground is warmed Here is a reference to that books.google.co.nz/books?id=o8cnwYUd96UC&lpg=PA53&ots=yvCj8oSsk&pg=PA57&f=false#v=onepage&q=&f=falseNote that water vapour displaces the heavier air it enters
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Post by steve on Oct 13, 2009 16:23:01 GMT
Yes "air containing moisture" is a bit sloppy.
The 0.5% difference in density was a rough figure based on starting from a kilo of air.
Yes, I assumed that one mole of H2O would be the same volume as one mole of N2.
The one set of figures I have in my head are that one mole of air has a volume of 22.4 litres at 0C and 25 litres at STP (20C ?). So that is a 0.5% change of density per degree difference.
Going back to my original calculation, roughly the difference in density would be 0.1% per 10% difference in relative humidity for air at STP.
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Post by radiant on Oct 13, 2009 16:44:15 GMT
Yes "air containing moisture" is a bit sloppy. The 0.5% difference in density was a rough figure based on starting from a kilo of air. Yes, I assumed that one mole of H2O would be the same volume as one mole of N2. The one set of figures I have in my head are that one mole of air has a volume of 22.4 litres at 0C and 25 litres at STP (20C ?). So that is a 0.5% change of density per degree difference. Going back to my original calculation, roughly the difference in density would be 0.1% per 10% difference in relative humidity for air at STP. OK if my 5/273 volume increase for 5 degree rise is correct which is 1.8% then: Human comfort humidity is about 40-50% On a hot sticky day when the humidity is very high then .5% difference via water is not unreasonable *and* we have to consider that columns of water vapour are entering the atmosphere displacing the surrounding air. So this is significant Also we know there is a big difference between the vapour pressure produced over cold water compared to warmer water so that at the poles there is almost no water vapour over the snow ice and water mixture present, but if any warming is introduced there will be more or less injections of concentrated water vapour as columns entering the atmosphere.
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Post by stanb999 on Oct 13, 2009 20:33:40 GMT
Radiant, the Santa Ana winds are caused by warmer wetter air from the gulf sliding over the mountains, then descending again. It really has noting to do with the affect you note. It's driven by large movements of air masses and the jet stream. So the initial force of the wind isn't created by the mountains as in your example of Greenland. In your example. cold high air moves down slope without regard for the larger atmospheric circulations. Yours is a quite extreme example. A simpler to demonstrate example is frost forms in the valley. Stanb99 You could be right for all i know but you are in conflict with other sources including for example wiki. en.wikipedia.org/wiki/Santa_Ana_windsThe Santa Ana winds do not originate in precipitation, but in the bone-dry high deserts.The sources are saying the force of the Santa wind comes from the fact the air is cooled in the high desert and then via gravitational force then crashes back towards the lower levels Wiki also says: Winds blowing off the elevated glaciated plateaus of Greenland and Antarctica experience the most extreme form of katabatic wind, of which the Santa Ana is a type, for the most part. The winds start at a high elevation and flow outward and downslope, attaining hurricane gusts in valleys, along the shore, and even out to sea. Like the Santa Ana, these winds also heat up by compression and lose humidity, but since they start out so extraordinarily cold and dry and blow over snow and ice all the way to the sea, the perceived difference is negligible.Wiki isn't the best source. Here is a simple explanation. meteora.ucsd.edu/cap/santa_ana.htmlYou may find this of use. www.atmos.ucla.edu/~fovell/ASother/mm5/SantaAna/winds.htmlAnother popular misconception that the winds are hot owing to their desert origin. Actually, the Santa Anas develop when the desert is relatively cold, and are thus most common during the cool season stretching from October through March. High pressure builds over the Great Basin (e.g., Nevada) and the cold air there begins to sink. However, this air is forced downslope which compresses and warms it at a rate of about 10C per kilometer (29F per mile) of descent. As its temperature rises, the relative humidity drops; the air starts out dry and winds up at sea level much drier still. The air picks up speed as it is channeled through passes and canyons.
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Post by stanb999 on Oct 13, 2009 20:38:08 GMT
Look up the katabatic winds of Iceland. Same thing.
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Post by radiant on Oct 13, 2009 21:12:38 GMT
Stanb99 You could be right for all i know but you are in conflict with other sources including for example wiki. en.wikipedia.org/wiki/Santa_Ana_windsThe Santa Ana winds do not originate in precipitation, but in the bone-dry high deserts.The sources are saying the force of the Santa wind comes from the fact the air is cooled in the high desert and then via gravitational force then crashes back towards the lower levels Wiki also says: Winds blowing off the elevated glaciated plateaus of Greenland and Antarctica experience the most extreme form of katabatic wind, of which the Santa Ana is a type, for the most part. The winds start at a high elevation and flow outward and downslope, attaining hurricane gusts in valleys, along the shore, and even out to sea. Like the Santa Ana, these winds also heat up by compression and lose humidity, but since they start out so extraordinarily cold and dry and blow over snow and ice all the way to the sea, the perceived difference is negligible.Wiki isn't the best source. Here is a simple explanation. meteora.ucsd.edu/cap/santa_ana.htmlYou may find this of use. www.atmos.ucla.edu/~fovell/ASother/mm5/SantaAna/winds.htmlAnother popular misconception that the winds are hot owing to their desert origin. Actually, the Santa Anas develop when the desert is relatively cold, and are thus most common during the cool season stretching from October through March. High pressure builds over the Great Basin (e.g., Nevada) and the cold air there begins to sink. However, this air is forced downslope which compresses and warms it at a rate of about 10C per kilometer (29F per mile) of descent. As its temperature rises, the relative humidity drops; the air starts out dry and winds up at sea level much drier still. The air picks up speed as it is channeled through passes and canyons. your links are agreeing with wiki that the Santa Ana is a katabatic wind. What is your point actually?? Your original point was that the Santa Ana was a precipitation created warm wind. Your links are saying the wind has its origin in the heights where the air cools and then descends by greater force by gravity than whatever force it arrives at the heights with Your second link has a faq which says: In my view, the best descriptive term for the Santa Ana winds is katabatic winds, which is Greek for "to flow downhill". As mentioned above, the Santa Ana air starts out relatively colder and more dense, and thus falls downslope
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Post by stanb999 on Oct 13, 2009 21:58:36 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.
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