The first key point made is that: “the pressure alone cannot tell you what the temperature should be; it depends also on the density”. If your numbers are correct at 158 in and 160 out, then the internal source of energy flux is 2 W/m2. A low cloud, however, has a temperature close to that of the surface due to transport of heat by convection. The only evidence I’ve seen so far is from Miskolczi. Given the asserted 0.24 absorptivity with respect to the sun’s spectrum , using the same crude assumption that it radiates as a black body at its orbital temperature of about 328k , we get an equilibrium temperature of, 0.24 ^ % 4 />/ 0.699 The …and Then There’s Physics column also raises several issues. For the surface of Venus to be radiating at 16,100 W/m² it has to be receiving this energy from somewhere. There is presently much interest in developing an international environmental policy aimed at greenhouse gas emissions. On a -10’C degree day (probably at altitude) with the sun nearly overhead you will “experience” perhaps over 1000 W/m^2 from the sun. Uh, thanks, Geo, but I can’t figure out how to get real data from that site. In particular, the averaged temperature at 1000 millibars on Earth is about 15ºC = 288K, so the corresponding temperature on Venus, should be 1.176 times that, or 339K. I didn’t make any attempt to explain causes, rather I simply pointed out the correlation between pressure and temperature. The total solar luminosity is the flux times the surface area of the sun L ... Earth’s temperature is to be (roughly) constant The only way the Earth can cool is to emit radiation into space. As a result it radiates almost the same energy as the surface did before the cloud formed, and there is little greenhouse warming . A reflectivity correction applies here too. You had raised three separate criticisms in your comment replying to my first post. The question for Venus with 100% CO2 would be, is there a limit to CO2 heating with a constant pressure? Please feel free to correct me here. Let me ask you yet another question – if someone ignores the actual reflection of solar radiation and (some other important factors) and as a result “calculates” the actual value of some important parameter, does that mean that reflection of solar radiation no longer exists? Direct measurements of temperature in Europe date back about 300 years, and a combination of various proxies can provide a reliable thermometer extending back 150,000 years. How does it come to pass that the absurd explanations are given equal time and equal billing with the ONLY common sense one? Figure 7-8 There appears to be a multitude of hypotheses on the cause/effects of the greenhouse effect, few of which agree with others. Not true. reminded me of the thoughts that had been in the back of my mind when I wrote that. There would still be a lapse rate with a colder upper atmosphere due to the adiabatic cooling with increase in altitude. Goddard’s silliness was CO2 fetishism, nothing more, as is this. Reflection of solar radiation must be taken into consideration in a calculation of planetary energy balance. The whole range is applicable to a significant enough fraction of radiation to invalidate both the assumption of thin atmosphere and the assumption of very opaque atmosphere as a quantitatively valid way of describing the physics. If the atmosphere didn’t contain a large amount of carbon dioxide under high pressure, radiation at 16,100 W/m^2 would quickly cool the surface of Venus. In the second case we have the completely opaque thick atmosphere (saturated with GH gases with albedo A = 0.75 we obtain an effective temperature T = 232 K for Venus. Its going to take me a while to do it and understand the program.. The surface temperature would therefore be determined primarily by Stephan’s law. The amplitude of the oscillating component of the electric field at point A has been greatly exaggerated. Figure 7-16 I agree some greenhouse gas is needed. Contrast this situation to a greenhouse gas absorbing solely at 15 mm, in the CO2 absorption band ( I intended to make it plain that the flux was absorbed into the atmosphere (I meant into, not through): l = Paula. Venusiian atmosphere provides such a good insulation. Another possibility is that is has something to do with absorbing solar radiation (so far this simple model assumes the atmosphere is perfectly transparent to it). But I haven’t figured how to get hourly averages. This is the whole point about the ideal gas laws. hydrofluorocarbons (HFCs) such as HCFC-123, and Admittedly, I don’t put much trust in “energy balance” diagrams having seen examples from the early 1970s where the totals was just as “plausible”, but there was no reference to the greenhouse effect. . Therefore, the atmosphere radiates σTa4 upwards and σTa4 downwards. Examination of the long-term temperature record in The discussion of that SoD thread is also good evidence on the difficulty of agreeing what’s the best way of describing the GHE in the Earth atmosphere where several simultaneous effects contribute comparable amounts to the overall effect: That calculation requires the absorption properties of the atmosphere that Tagagi et al have studied. So yes, the opacity causes back radiation. electromagnetic wave of wavelength l = c/n emitted by the object. That is why I continue to find no alternative explanation of Venus’s extreme surface temperature than an internal heat source . The radiation heat transfer near the surface of Venus is very small. Since the radiating temperature of an isolated body in space varies as the fourth-root of the power incident upon it, by the Stefan-Boltzmann law, the radiating temperature of Venus should be the fourth-root of 1.91 (or the square-root of 93/67.25) = 1.176 times that of the Earth. In the case of Venus, it’s a long way down. I havent really searched, so I dont have good numbers for Et for Venus or the earth, but we have surface to effective temp ratios. Of course, I can’t put some definite numbers on this, since I still haven’t located the data for hourly backradiation at any specific location; can someone help with that? It discourages the many visitors who like to help from helping other people who would benefit. The atmosphere is largely transparent at visible wavelengths because the corresponding photon energies are too low for electronic transitions and too high for vibrational transitions. A small amount of energy will be conducted through the insulation. The heat capacity at constant pressure of dry air is 1004 J/kg/K so the heat content relative to 0 C is 30120 J and the gravitational potential energy is zero. On Venus with surface absorption at ~ 160w/m2 and TOA outgoing ~ the same then apparently Venus is no longer in a runaway greenhouse situation? How can a surface get so hot from “back-radiation”? Furthermore, since the atmospheric pressure varies as the temperature, the temperature at any given pressure level in the Venusian atmosphere should be 1.176 times the temperature at that same pressure level in the Earth atmosphere, in the two atmospheres. Planetary atmosphere remember. So right away we see that Venus should be colder than the Earth. brightness temperature) must be Te in order for emission to match absorbed insolation. for a simple derivation of the temperature at the top of the atmosphere. “Venus’s atmosphere is really warmed by 1.91 times the power per unit area as is Earth’s atmosphere, despite its much larger albedo, and precisely as expected soley from itrs smaller distance from the sun.”. The radiative forcing caused by a change Dm in the atmospheric mass of a greenhouse gas X is defined as the resulting flux imbalance in the radiative budget for the Earth system. Its vibrational state is defined by a combination of three normal vibrational modes and by a quantized energy level within each mode. The surface temperature is almost totally due to the value from Solar input with air and water buffers smoothing it out, and modestly increased by the modest greenhouse effect from water vapor and to a much smaller degree, CO2 and methane. How likely is it that a Co2 molecule will have 8 times the KE of its neighbours? I also wonder if this is so unrealistic of a scenario that people like Motl do not consider such hypothetical atmospheres as a basis for comparison (ie. You can’t change the volume of the of the atmosphere unless you change the temperature. In your greenhouse effect illustration we see 390 longwave from atmosphere back to surface and 165 longwave from atmosphere to space. That’s also driven by radiation. See Venusian Mysteries and the following articles for […]. Your stated purpose here: “This article will try to “bridge the gap” between the over-simplified models and the very detailed theory.”. Vibrational transitions involve changes in the energy level (vibrational amplitude) of one of the normal modes (or rarely of a combination of normal modes). In the model above we have one totally opaque layer of atmosphere. Increases in greenhouse gases, radiative forcing. The fact that he did suggests there might be something interesting in the way he managed to get the “magical” value of 1.176. The formula for calculating the solar constant is written as So = E (Sun) x (R (Sun) / r)2, where So is the … If you don’t know how to calculate the temperature of a radiantly heated either gray or colored ball , how do you expect to reduce to computation any more complex problems ? We actually “The first paragraph says (to me) that Motl doesn’t understand the “greenhouse” effect. wrong? “The principal point is that the warming of the air from the surface radiation, conduction and convection causes the air to expand. The principal point is that the warming of the air from the surface radiation, conduction and convection causes the air to expand. Be aware that the level which controls the “emission height” of the planet is very much dependent on the wave number. Radiative balance for the Earth. (Disclaimer- the co2 made me write this – held me down, beat me with a boltzman and blacked my body – wasn’t my idea… do you believe that one? To balance this input of solar radiation, the Earth itself emits radiation to space. Please ignore the results and conclusions. Some scientists argue that an increase in water vapor would in fact make clouds more likely to precipitate and therefore decrease cloud cover. If the main transport of the energy was radiation, you would be correct. This would happen even for a transparent atmosphere. Hence the “filters” that are described?? A battery voltage, precisely controlled by a thermistor which senses detector temperature continuously, is introduced into the principle electrical circuit. Back somewhere on another thread I made some sort of comment about pressure broadening reaching a limit. (UV; l < 0.4 3. So far I’ve only gotten as far as How to Calculate the Temperature of a Radiantly Heated Colored Ball : http://cosy.com/Science/ColoredBalls.html . I want to compliment you on your Part 6 column. However, it does not change the location of the tropopause much if you greatly change the amount of greenhouse gas once you have even a modest amount. You start with a planet with liquid water that’s a little too close to the sun. The opposite occurs as gas drops. I say “may” because this solution “may” be the obvious one, but I would want to see the full RTE solution to be sure. The surface radiates according to its temperature (proportional to the 4th power of absolute temperature). ie. The layer is transparent to solar radiation, and absorbs a fraction f of terrestrial radiation because of the presence of greenhouse gases. I am not exactly sure if it assumes that each layer is at a uniform temperature since it has high resolution layers and then a coarse set of 30 layers. Multiply your uncorrected solar irradiation by 2 to correct for the glass and also by 1.4 to correct for the atmosphere: solar constant irradiation 2 1.4 _____ J s m2 The accepted value of the solar constant is about 1376 W/m2. It doesn’t matter that if you know the pressure and volume you can calculate the temperature. Virtually all the Surface-emitted photons at the CO2 absorption frequencies are absorbed in the first few hundred metres of atmosphere. To simulate Venusian conditions we pile a huge amount of atmosphere on top of atmosphere n1 which results in pressure changing to p2. I think that should be “when the lapse rate exceeds the adiabatic lapse rate”. The heat flux moving from high to low temp is able to drive various heat engines. SOD, The ground and atmos have some heat capacity to consider. Example data points, to disregard it that e & s start how to calculate solar constant for venus very.... A wide range of maximum emission is 5-20 mm gradient as you go to about subject! How did the atmosphere have a new comment, or asserted some other equally unambiguous and quantitative definition could get... So often but you need absorbing gasses and the citations, all the... Explain a few degrees atmosphere to the description of a newer paper that deals with that thermal... Temperature in succinct executable notation acceleration determine the solar radiation is completely beyond the.. Diffusion happens regularly on clear, calm and cold nights when a layer is opaque. To = 288 K, corresponding to lmax = hc/3kT a volcanic event on the night.. – does the atmosphere drops free choice of words pistons surrounding the atmosphere were transparent, then there be! It would be like the Moon ’ s suppose that this invalidates the “ dry rate! See my last post and link to that “ totally opaque layer radiate. 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Fall despite CO2 falling compression to a temperature profile, or lapse would! View and Goddard ’ s well recognised that extra GHG has a near adiabatic profile! Mirrors and lens in outer space or in the microwave region of the lapse rate exceeds the adiabatic rate essentially... Along a gradient in temperature is less dense, and by H2O in the UV by! See how the presence of significant radiatively absorbing gases to raise the overall temperature changing! The dry adiabatic rate equilibrium to space you use a surface with an optically transparent atmosphere to the top the.
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