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Post by steve on Sept 22, 2009 11:56:26 GMT
We need to agree basic terms. The adiabatic lapse rate is the rate of temperature fall as a parcel of air moves upwards in the atmosphere Agreed. Agreed. And a dry atmosphere has a lapse rate of about 10C per kilometre rise. Whether the atmosphere as a whole descends in temperature at the lapse rate as you go higher is also dependent on other processes within the atmosphere. This is the point we are discussing. I'm not disagreeing with what you say. What I am saying is that because the troposphere has a lot of convection it tends towards having a temperature profile that is similar to the lapse rate. Essentially, because the sun heats the atmosphere from below, the atmosphere will start by having warmer air below which will encourage convection which leads to enough mixing to cause the atmosphere to have a temperature profile that is similar to the lapse rate. If there were a process that resulted in the sun heating higher layers, then this would tend to suppress convection because the parcels of air would not be able to rise as much. This happens in the stratosphere and I'm guessing it would happen if there is a lot of dust or soot aloft. The lack of convection would reduce mixing and would mean the temperature profile of the atmosphere were constrained by different processes. Whether the proposed N2/O2 atmosphere has a similar profile may depend on whether it has sufficient heating at the surface to encourage convection.
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Post by radiant on Sept 22, 2009 12:42:01 GMT
We need to agree basic terms. The adiabatic lapse rate is the rate of temperature fall as a parcel of air moves upwards in the atmosphere Agreed. Agreed. And a dry atmosphere has a lapse rate of about 10C per kilometre rise. Whether the atmosphere as a whole descends in temperature at the lapse rate as you go higher is also dependent on other processes within the atmosphere. This is the point we are discussing. I'm not disagreeing with what you say. What I am saying is that because the troposphere has a lot of convection it tends towards having a temperature profile that is similar to the lapse rate. Essentially, because the sun heats the atmosphere from below, the atmosphere will start by having warmer air below which will encourage convection which leads to enough mixing to cause the atmosphere to have a temperature profile that is similar to the lapse rate. If there were a process that resulted in the sun heating higher layers, then this would tend to suppress convection because the parcels of air would not be able to rise as much. This happens in the stratosphere and I'm guessing it would happen if there is a lot of dust or soot aloft. The lack of convection would reduce mixing and would mean the temperature profile of the atmosphere were constrained by different processes. Whether the proposed N2/O2 atmosphere has a similar profile may depend on whether it has sufficient heating at the surface to encourage convection. It seems you are wanting to say something about the lapse rate and the rate of convection. But i am not sure what you are saying about that Why are you talking about a dry lapse rate? I notice that the dry adiabatic lapse rate is 9.8degree per kilometer The lapse rate is whatever it is measured to be wherever it is measured no matter what air you pass thru. I think you mean something to do with the dry adiabatic lapse rate which is the temperature that a parcel of air taken from the surface to 10km would have when no heat was lost or gained? If some meaning is to come out of amounts of convection and observed lapse rates we need to also recognise that as the same amount of a air in the atmosphere rises its heat content per cubic meter falls at some known rate because at 18000 feet air is half the surface pressure and so contains half the matter the surface contains. A thermometer in contact with the air only can measure what it is contact with or what is radiated onto the surface of the device Meaning that on earth if you expand the gas to twice the volume you get a fall in temperature as measured and if you compress it you should get the same temperature again Anyway the dry adiabatic lapse rate is 9.8degree per kilometer I can see that this means it has 10 g per kilogramme of air That is 10 g in about .9m3 of air or 900 liters of air My brain is hurting at this point. Can you elaborate what you are getting at
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Post by steve on Sept 22, 2009 13:56:09 GMT
What I said was that the temperature profile of the atmosphere would be similar to the DALR on our earth - 10C per km is close enough - but only if convection is still an important process.
You said "Adiabatic lapse rate does not apply to air that is mixed" which is technically true, but doesn't conflict with what I said.
In our atmosphere we have a region with convection - the troposphere - whose temperature profile approximates to the adiabatic lapse rate (dry or moist), and a region without convection (the stratosphere) whose temperature profile doesn't.
I'm talking about dry lapse rate because you're talking about an atmosphere with no water vapour.
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Post by radiant on Sept 22, 2009 15:18:46 GMT
What I said was that the temperature profile of the atmosphere would be similar to the DALR on our earth - 10C per km is close enough - but only if convection is still an important process. You said "Adiabatic lapse rate does not apply to air that is mixed" which is technically true, but doesn't conflict with what I said. In our atmosphere we have a region with convection - the troposphere - whose temperature profile approximates to the adiabatic lapse rate (dry or moist), and a region without convection (the stratosphere) whose temperature profile doesn't. I'm talking about dry lapse rate because you're talking about an atmosphere with no water vapour. I guess what we need to establish for some different temperatures is which is lighter? Warm air or slightly colder air a few mm above it? We should be able to figure that part out for various temperatures and air pressures. Then there is the issue of temperature measurement. The black body emission temperature of our own atmosphere very high up is hundreds of degrees centrigrade. But there is almost no atmosphere up there. If you put a thermometer up there it is not going to be hot because it radiates more energy to space than it can receive from the emission going on up there. Similarly if you measure the temperature of a metal roof on a warm dryish clear sky night it will be around 10 degrees cooler than the warm air temperature because the roof radiates to space and there is very little emission from the air around the roof. Google Nightcool if you have not seen my other posts on this. So if we measure the temperature with thermometers we will get different temperatures than if we do it via distance methods On the earths surface we measure 'air temperature' in a stevenson screen that either radiates more heat than it receives or recieves more heat than it radiates and the thermometers inside then receive the internal radiation of the shelter plus the conduction from the almost unpresent air. If we send stevenson screens up into the atmosphere we measure solar, terrestial and atmospheric radiation and the even less present airs contact. What do we measure?? And just to show you can learn something new every day www.universetoday.com/2006/01/20/satellites-on-a-budget-high-altitude-balloons/Balloon photograph taken from 25km "At these altitudes, air pressure is only 1% of that at ground level, and air temperatures are approximately -60 degrees F," he said. "These conditions are closer to the surface of Mars than to the surface of Earth." Even so i am not sure what we are measuring when we record these different numbers
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Post by tobyglyn on Sept 23, 2009 0:55:37 GMT
That was really interesting - thanks!
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Post by tobyglyn on Sept 23, 2009 3:49:56 GMT
Here's a more recent mission from a different team : "A group of US science students have upstaged NASA by sending a camera into near-space to take pictures of Earth using off-the-shelf items costing just $US150 ($170). Displaying stunning ingenuity reminiscent of MacGyver, the MIT students filled a weather balloon with helium and strapped it to a styrofoam beer cooler containing a cheap Canon A470 camera that was programmed to take photos every five seconds. The students - Oliver Yeh, Justin Lee and Eric Newton - placed hand warmers inside the beer cooler to ensure the camera and battery did not freeze in the -40-degree temperatures." www.smh.com.au/technology/sci-tech/macgyver-students-send-170-camera-into-space-20090923-g1kn.html?autostart=1
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Post by spaceman on Sept 23, 2009 14:18:08 GMT
Once upon a time there was a simple yet complex idea related to weather. The sun heats the earth, which is about 70% water. The water gets warm and forms vapor. The water vapor rises condenses and falls as rain or snow. Releasing heat? Is that the heat cycle? When the rain falls over land, runs into rivers that we dam up and convert the energy back into electricity. Is this right so far? So, if co2 is making the this place hotter, then it would make sense that there would be more water vapor, and as a result more rain. It is still -60 degrees up there or cold enough to make a temperature gradient. So even when co2 retains heat, it would give up the heat albeit more slowly, but surely, causing more water vapor. Energy is not created or destroyed in this cycle, it goes somewhere, into space. I think this feedback system keeps the earth within certain temperatures. The weather never repeats exactly, it more like ryhmes. On a dry planet, enough co2 would probably cause the kind of warming, add water to the mix and it's a different story. When you spray water on a fire it cools it down. Rain will knock down the hottest forest fire. Isn't that what happens off the coast of California? A high pressure system sits off the coast, allowing the water to become warm. As the air becomes full of water vapor, it developes a low pressure system. Low pressure also causes sea water to boil, so it adds to the amount of water in the air. The pressure gradients are pulled on shore and California has rain. Eventually it plays its self out and the cycle starts all over again. I have a lot of doubts about the cause and effect of co2 on atmospheric warming. Somewhere, it'd rain an awfull lot.
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Post by nautonnier on Sept 26, 2009 14:28:44 GMT
What I said was that the temperature profile of the atmosphere would be similar to the DALR on our earth - 10C per km is close enough - but only if convection is still an important process. You said "Adiabatic lapse rate does not apply to air that is mixed" which is technically true, but doesn't conflict with what I said. In our atmosphere we have a region with convection - the troposphere - whose temperature profile approximates to the adiabatic lapse rate (dry or moist), and a region without convection (the stratosphere) whose temperature profile doesn't. I'm talking about dry lapse rate because you're talking about an atmosphere with no water vapour. I guess what we need to establish for some different temperatures is which is lighter? Warm air or slightly colder air a few mm above it? We should be able to figure that part out for various temperatures and air pressures. Then there is the issue of temperature measurement. The black body emission temperature of our own atmosphere very high up is hundreds of degrees centrigrade. But there is almost no atmosphere up there. If you put a thermometer up there it is not going to be hot because it radiates more energy to space than it can receive from the emission going on up there. Similarly if you measure the temperature of a metal roof on a warm dryish clear sky night it will be around 10 degrees cooler than the warm air temperature because the roof radiates to space and there is very little emission from the air around the roof. Google Nightcool if you have not seen my other posts on this. So if we measure the temperature with thermometers we will get different temperatures than if we do it via distance methods On the earths surface we measure 'air temperature' in a stevenson screen that either radiates more heat than it receives or recieves more heat than it radiates and the thermometers inside then receive the internal radiation of the shelter plus the conduction from the almost unpresent air. If we send stevenson screens up into the atmosphere we measure solar, terrestial and atmospheric radiation and the even less present airs contact. What do we measure?? And just to show you can learn something new every day www.universetoday.com/2006/01/20/satellites-on-a-budget-high-altitude-balloons/Balloon photograph taken from 25km "At these altitudes, air pressure is only 1% of that at ground level, and air temperatures are approximately -60 degrees F," he said. "These conditions are closer to the surface of Mars than to the surface of Earth." Even so i am not sure what we are measuring when we record these different numbers Radiant, You are making the mistake of considering the atmosphere as something static. Once the air starts moving it has significant momentum it does not rely solely on its buoyancy once convection is in progress it will often run past its buoyancy point and even past the cooling points as convection can be so fast that the air 'bubbles' which can be extremely high humidity have had no time to cool. The air currents that recently caused the Air France aircraft to crash were estimated to have been moving upwards at more than 100 miles per hour. For example from another report: According to the memo written by one of the crew, the twin-engine Northwest jet was cruising at 39,000 feet when it "approached a large area of rain below us." The plane's weather radar indicated only light precipitation or perhaps ice crystals straight ahead. The memo recounts how pilots were surprised to see substantial rain "streaming up the windshield" at that altitude and "the sound of the plane getting pelted like an aluminum garage door."online.wsj.com/article/SB124607165106964441.html#mod=article-outset-boxso at 39,000ft the aircraft was in air that the ICAN standard lapse rate would have at ~ -56C yet the aircraft was hit with liquid water droplets. The atmosphere is not a mathematically perfect medium with a precise tropopause and a standard easy to understand lapse rate. Yes you can average out to a standard like ICAN but in many respects it may only be as useful as averaging the color of cars on an interstate.
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Post by trbixler on Sept 26, 2009 15:19:25 GMT
One could imagine many boxes each governed by PV=NRT , each box has a potentially different mix of gasses and each box is moving as nautonnier has suggested. Of course each box has mass so momentum is part of the convection process. Trivial math, so trivial that most want to talk about well mixed gasses and columns etc. Note the velocity of the boxes can and will be in any direction. Additional note the density of each box (comprised of differing gasses) will have differing energy absorptive properties.
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Post by trbixler on Sept 27, 2009 16:00:59 GMT
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Post by radiant on Sept 28, 2009 8:26:09 GMT
I guess what we need to establish for some different temperatures is which is lighter? Warm air or slightly colder air a few mm above it? We should be able to figure that part out for various temperatures and air pressures. Then there is the issue of temperature measurement. The black body emission temperature of our own atmosphere very high up is hundreds of degrees centrigrade. But there is almost no atmosphere up there. If you put a thermometer up there it is not going to be hot because it radiates more energy to space than it can receive from the emission going on up there. Similarly if you measure the temperature of a metal roof on a warm dryish clear sky night it will be around 10 degrees cooler than the warm air temperature because the roof radiates to space and there is very little emission from the air around the roof. Google Nightcool if you have not seen my other posts on this. So if we measure the temperature with thermometers we will get different temperatures than if we do it via distance methods On the earths surface we measure 'air temperature' in a stevenson screen that either radiates more heat than it receives or recieves more heat than it radiates and the thermometers inside then receive the internal radiation of the shelter plus the conduction from the almost unpresent air. If we send stevenson screens up into the atmosphere we measure solar, terrestial and atmospheric radiation and the even less present airs contact. What do we measure?? And just to show you can learn something new every day www.universetoday.com/2006/01/20/satellites-on-a-budget-high-altitude-balloons/Balloon photograph taken from 25km "At these altitudes, air pressure is only 1% of that at ground level, and air temperatures are approximately -60 degrees F," he said. "These conditions are closer to the surface of Mars than to the surface of Earth." Even so i am not sure what we are measuring when we record these different numbers Radiant, You are making the mistake of considering the atmosphere as something static. nautonnier I think you must have got confused by what i said. I know air has momentum. I know air cannot be considered as something that is static. I think you are maybe mixing my comments to Steve? about a pure n2 o2 argon atmosphere? Even that atmosphere will have wind and so forth. And i already earlier mentioned aircraft avoiding areas of strong air movement because they will break up. solarcycle24com.proboards.com/index.cgi?board=globalwarming&action=display&thread=851&page=1#30287
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Post by northsphinx on Sept 28, 2009 9:28:24 GMT
So it is all about the clouds.
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Post by radiant on Oct 10, 2009 16:44:03 GMT
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Post by steve on Oct 12, 2009 17:12:06 GMT
On another thread: You were totally unable to grasp the principals behind the adiabatic lapse rate which involves a parcel of air expanding with momentum and iertia into the surrounding air, and therefore little mixing, while it ascends upward into the atmosphere. Again and again you used the word adiabatic when you should have just used lapse rate. Again and again you wanted to deny the phenonema was possible to exist or wanted to minimise its importance Apparently your own theories were more important than anything else anybody had ever measured and witnessed before. You have a long memory for arguments where you got the wrong end of the stick. I said "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)." There are two distinct nouns here. 1. "temperature profile of the atmosphere" 2. "adiabatic lapse rate". The former is what is measured. The latter is an idealised calculated quantity. If there is no convective mixing in the atmospher, there is little reason why there should be any relationship between the former and the latter. Eg. in the stratosphere. Hence the qualification "if the atmosphere continues to be convectively mixed". You didn't realise the difference and couldn't understand why I thought it was relevant to your discussion. I gave up when you started getting sarcastic. PS. Saying that the latter "determines" the former was a bit strong (but it was not a central point either of what I was trying to say or what you were disputing).
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Post by radiant on Oct 12, 2009 17:35:16 GMT
On another thread: You were totally unable to grasp the principals behind the adiabatic lapse rate which involves a parcel of air expanding with momentum and iertia into the surrounding air, and therefore little mixing, while it ascends upward into the atmosphere. Again and again you used the word adiabatic when you should have just used lapse rate. Again and again you wanted to deny the phenonema was possible to exist or wanted to minimise its importance Apparently your own theories were more important than anything else anybody had ever measured and witnessed before. You have a long memory for arguments where you got the wrong end of the stick. I said "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)." There are two distinct nouns here. 1. "temperature profile of the atmosphere" 2. "adiabatic lapse rate". The former is what is measured. The latter is an idealised calculated quantity. If there is no convective mixing in the atmospher, there is little reason why there should be any relationship between the former and the latter. Eg. in the stratosphere. Hence the qualification "if the atmosphere continues to be convectively mixed". You didn't realise the difference and couldn't understand why I thought it was relevant to your discussion. I gave up when you started getting sarcastic. PS. Saying that the latter "determines" the former was a bit strong (but it was not a central point either of what I was trying to say or what you were disputing). You still cant understand it 1. The lapse rate is an observed temperature fall with altitude. It is the temperature falling rate where it is observed to fall. Much of the fall in temperature occurs because water is radiating heat out of the atmosphere that is gained at the surface. Surface conductively warmed air is observed to fall in temperature while there is water in the atmosphere. When there is almost no water in the atmosphere the atmosphere does not have a lapse rate. Instead it has a rise rate. 2. The adiabatic lapse rate is what you get when you take a parcel of air and move it upwards in the atmosphere. Therefore: 1. Is what is observed to be present due to loss of heat from the atmosphere where 98.99% of the atmosphere has no ability to radiate heat unless it is cooled by contact with 1% water or the other .01% 2. involves the word 'adiabatic' www.google.co.nz/search?hl=en&source=hp&q=define%3A+adiabatic&meta=&aq=f&oq=Adiabatic means no loss or gain of heat. Therefore there is no adiabatic lapse rate from the surface of the earth to the top of the trophosphere. There is just a fall in temperature rate called the lapse rate. Therefore an atmosphere without the ability to radiate heat that is warmed at the surface by touching the earths surface will rise in temperature with altitude because temperature means that each molecule has energy that in this case cannot be released and the molecules with the highest energy will rise higher than the ones with least energy. Colder and yet warm molecules will sink. Higher energy means lighter in this case. Hydrogen and Helium are so light they escape earths gravity. If the earth became hotter, then in the exstreme case water which is a light atmospheric gas would move upwards thru the atmosphere and would not form ice and would escape to space. Fortunately cold air has almost no ability to hold water and therefore we still have water on earth. And it is water that is principally cooling the atmosphere even when it is hardly present.
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