Discussions on pyrgeometers (IR measurement), Part 2

Posted: April 21, 2013 by tchannon in Measurement, Surfacestation
Image

Courtesy Physikalisch-Meteorologisches Observatorium Davos
Radiation instrument with cover removed

Since I have just made available numeric data which will add meat to talk about pyrgeometers and how heat behaves and travels in the atmosphere, a continuation of a long Talkshop thread can take place here. If you want to comment on what the Chilbolton data means, then this is the thread.

Original thread is here.

Image

The above is from actual data 20th April 2013, as though a flux is emitted from a body at T given perfect emissivity.

I hazard a guess the flattening of the rise after dawn until about 8am with a kink is humidity burning off, followed a couple of hours later by a few small clouds, which then vanished. One of the sky thumbnails captured a cloud. (wouldn’t be the same ones I spotted here, far too small)

Middle of the day and evening a spot IR thermometer measured -31C at zenith here.

Solar not at zero? Slight configuration error.

Posted by Tim Channon

Comments
  1. Richard111 says:

    Have been watching site linked below for some years now. Don’t know how accurate but changing solar levels through the year show up clearly. Also difference in solar energy with regard to humidity and or haze. The site is only a few hundred yards from my home so usually see effects of clouds first hand. Changes in total insolation can be mind boggling.

    http://www.milfordweather.org.uk/solar.php

  2. tallbloke says:

    There’s an interesting chat http://clivebest.com/blog/?p=4871“>going on here at the moment about water vapour.

  3. AlecM says:

    Pyrgeometers do not measure a real energy flux. They measure a potential energy flux, the S-B power for the apparent temperature of the emitter(s) in the view angle. This is the energy it could emit to a sink at absolute zero. In the case of a normal temperature gradient, near equal surface and air temperatures in the emission depth, all that potential energy, the radiation field, is annihilated at the Earth’s surface.

    With no convection or evapo-transpiration, the surface would emit IR with an operational emissivity of ~0.4, 1/3 rd in non self-absorbed GHG IR bands and the rest in the atmospheric window. The rest is net zero. The explanation is a bit of physics no-one in Climate Alchemy has apparently realised exists. Correct for parallel convection and evapo-transpiration and the predicted average emissivity = 0.4 * 63/160 = 0.158. This is identical to the real value, 63/396 = 0.159: the experimental data are very good.

    Also pyrgeometers cannot work as claimed. This is because the sensor would have to cool to well below the temperature of the case [assumed to be local air temperature] for the outgoing atmospheric window IR to equal the incoming IR outside the AW. Hence they are now sneakily introducing thermistors to measure internal convection. All in all, they are a desperately bad instrument used by Meteorologists solely because they are taught the false ‘back radiation’ concept – incorrect physics. Bolometers are absolute.

    The real physics is that the conversion to heat from radiation is the integral over all wavelengths of the divergence of the monochromatic radiative flux density. So heat flow is the negative of the difference of radiative energy fluxes over all wavelengths at a point. This gives the S-B equation difference but with qdot = – delta I where I is irradiance. Few scientists understand this, nor do they realise that the second term of the S-B difference does not prove ‘back radiation’.

    And what’s worse, lots of physicists no less imagine the two bodies shoot photons at each other when there is no such thing – Planck hated the idea. All that can be claimed is that the photonic quantum transfer is to or from the net radiation field at a particular wavelength at a point at an instant.

    100s of man years have been wasted in the Trenberth Energy Budget. To offset the back radiation they then claim that Kirchhoff’s law of radiation applies at ToA. 333 – 238.5 is created out of thin air and 40 comes from the surface. Thus they exaggerate warming by a factor of 157.5/23 = 6.85. They then correct for the wrong temperature by hind casting with imaginary extra cloud albedo [~twice real optical depth for low level clouds] and the net result is the imaginary positive feedback because you get more evaporation in the artificially warm sunlit ocean compared the artificially cold cloudy ocean.

    This is the biggest mass self-delusion in scientific history and it’s time it was shut down before more money is wasted!

  4. oldbrew says:

    AlecM says: ‘This is the biggest mass self-delusion in scientific history’

    Since phlogiston theory anyway…
    http://en.wikipedia.org/wiki/Phlogiston_theory

  5. Richard111 says:

    AlecM, thank you for your comment (and TB 🙂 ), much food for thought.

    Phlogiston, reminded me of the ‘corpuscles’ which our early hero’s seemed unaware that they were subject to the law of gravity and then confused people about ‘dark emanations’.

  6. tchannon says:

    AlecM,

    You are caught by the counter-intuitive.

    In the past I have repeatedly been in the unpleasant position of being in the middle between two loud groups of individuals who preach but both have it wrong. Whole thing is silly given there is nothing to be worried about. I don’t know of any complete solution to misunderstanding which is deep.

    I don’t want to put your back up but neither can I allow that to stand. See the problem, if I counter you you will dig your heels in or exit. Same thing can happen with people holding an opposite position.

    You wrote “Pyrgeometers do not measure a real energy flux.”

    Exactly what does that mean? Therein lies the start of misunderstanding.

    These particular pyrgeometer are attempting to quantify an internal system value where to a degree they succeed. Unfortunately there are many defects.

    In addition I consider the whole earth heat problem to be unknowable. I do though think it is worth clarifying a mess so it is seen as a mess.

    Now if you look at the Chilbolton information I have just made available, the 12 plots, the one bottom right, that ought to answer your question, if you actually asked. The plot is for two part thermal factors, been summed.

    The answer is still grossly incomplete.

  7. A C Osborn says:

    tallbloke says: April 22, 2013 at 9:00 am, that is a really interesting discussion, especially the corroborating data.
    And your last comment LOL.

  8. mkelly says:

    Richard111 says:

    April 22, 2013 at 8:18 am

    Richard I looked at the link you provided and my main question is why you folks did not die on the third day of sunshine. The third day (the hump over the 20/4/2013) shows an average of 150 w/m^2. That is a very low temperature. Plus how did you survive the 4th or so days when the w/m^2 were above 700 w/m^2 which would be a very high temperature. How do you survive? 🙂

  9. AlecM says, April 22, 2013 at 9:20 am

    Even though I thought we had exhausted this topic, I cannot let AlexM’s comment go unchallenged.

    Despite all his convoluted ‘physics-speak’ the fact remains that pyrgeometers exist, are installed all over the world, and do definitely measure the downwelling radiation component of the LWIR radiation fluxes that are exchanged between the surface and the atmosphere.

    Making an assertion that pyrgeometers ‘cannot work as claimed’ is just his opinion based on a philosophical position that some physicists do adopt (and others do not) that only the net difference of the up and down radiation exists and that the ‘up bit’ and the ‘down bit’ do not (a position that seems to some of us like a logical contradiction!)

    In the case of the surface-atmosphere interface, the difference between flux up and flux down (assuming, simply for the sake of concrete example, Trenberth’s figures of 356Wm-2 up and 333Wm-2 down) is a net energy flow of 23Wm-2 upwards. Since this is in the direction from a hotter to a cooler body, the laws of thermodynamics are not violated. Also there is no justification whatever for warmists to claim that this causes any ‘positive feedback effect’ resulting in further warming.

    Whether warmists do make such unsupportable assumptions in the face of simple radiative exchange concepts that date from Prevost’s Theory of Exchanges (1790) is beside the point. For skeptics to deny that back radiation exists and to claim that pyrgeometers don’t work is in my opinion utterly counterproductive in the fight against warmism. It is surely always foolhardy to try to combat one untruth with another.

  10. tallbloke says:

    ACO; The bit that got me was Anthony’s response to my solar interjection about water vapour:

    “I see no sun to CO2 connection here.”

    CO2? Who mentioned CO2?

    “There is no corresponding step change in solar data in 1998.”

    There was a thucking great El Nino though, and outgoing tropical OLR shot through the roof. No shortage of high atmosphere water vapour there.

  11. Richard111 says:

    mkelly says:
    April 22, 2013 at 2:40 pm

    “How do you survive?”

    Well, that’s Pyrgeometers for you. Life becomes unknowable. 🙂

  12. Richard111 says:

    Talking of CO2 (TB at 2:47), NASA thinks CO2 is a coolant.

    http://science.nasa.gov/science-news/science-at-nasa/2012/22mar_saber/

  13. AlecM says:

    @David Socrates

    1. Pyrgeometers cannot work as claimed for a clear sky because the sensor is emitting energy to space via the atmospheric window and receiving energy outside the AW. For an atmosphere at 15 °C, I estimate the sensor has to cool to -13.5 °C. In practice, convection occurs.

    This is why Philipona and others have incorporated thermistors to measure convection: stoffel_t.pdf

    Philipona et al. (3-coefficients)
    Win = K1 Vtp + σT4case + K3 σ (T4dome – T4case) + K4 σ Vtp T3case [4]
    Reda et al. (4-coefficients)
    Win = K0 + K1 Vtp + K2 σT4receiver + K3 σ (T4dome – T4receiver) [5]
    where,
    Treceiver = Tcase + 0.0007044 Vtp

    Doesn’t work as claimed…….!

    As for the theory: qdot at a point = minus integral [delta monochromatic radiative flux density] over all wavelengths.

    The composite wave fronts have to combine destructively before work can be done. You can’t use the two stream approximation at an optical heterogeneity like Trenberth does.

    To imagine that S-B1 – S-B2 means two opposing radiation streams is completely unphysical. I have seen S-B equations expressed as predicting radiative heat transfer rate.when in reality for a semi-transparent emitter like the atmosphere you must use the Planck Irradiation Function convolved with the emissivity at each wavelength or number. This is what an FTIR measures and what MODTRAN predicts.

    The models overestimate absorbed surface IR by a factor of 6.85 [2009 Energy Budget] which is why they go wrong. Sorry – someone has to state tat this emperor has no clothes and if you want to check, read a 1st rate text like goody and Yung.

  14. AlecM says:

    PS I explained originally how the assumption of Kirchhoff’s law of radiation applying at ToAS is completely wrong. it’s needed to offset the Trenberth 333 W/m^2 which does not exist as a real energy flux. it creates a perpetual motion machine of the 2nd kind, the lower atmosphere using its own heat to cause itself to expand.

    The only down IR is from Ozone. You can prove all this from MODTRAN which only fails by missing out minor frequency conversion in clouds which offsets the CO2 – ‘bite’ in OLR.

  15. AlecM,

    The flow that offsets Trenberth’s 333Wm-2 downwelling radiation from atmosphere-to-surface is Treberth’s 356Wm-2 upwelling radiation from surface-to-atmosphere, leaving a residual 23Wm-2 of what you would call ‘real’ radiation from surface to atmosphere, warmer to cooler. Dispute Trenerth’s actual figures if you will (do you have better ones?) but don’t confuse that issue with the issue of whether warmists are using bad physics in their attempt to prove their dubious warming case.

    The two issues are separate but you are attempting to conflate them: a bad argument over pyrgeometers confronting a bad argument from the warmists.

  16. kuhnkat says:

    Stephan Boltzman is an equation based on an ideal black body. To make it work in real life it uses a parameter called emissivity. For solids and water the emissivity can be close to 1.

    Why am I boring you with this information you probably know?? Well, have you actually THOUGHT about what it means??

    Trenberth and many others use 1 or .99 as the emissivity in their computations. This isn’t that good even for the surface as the emissivity can go down to .9. It DOES make a small difference. Now, how do you determine the emissivity of the atmosphere?? Trenberth and others use 1 or very close to 1 for the atmosphere also. Only with heavy clouds present is this even close. Since 40% of the earth is not cloud covered it makes a BIG difference. I have seen reasonable estimates of the EARTH from space at .7. This is including all bands and radiation from the ground. So, if the WHOLE planet is only .7 what is the REAL emissivity of the atmosphere??

    Doesn’t say much for those junk Trenberth graphs and the 390 up 365 down or whatever!!

    [mod: author accidentally mixed in IR thermometers here, see comment –Tim]
    Those toy pyrgeometers are wired with SB. The good ones allow adjustments for emissivity. Who knows the emissivity of what they are measuring?? Mostly they are toys to allow people to fool themselves. The ones I have looked at cover the window plus some water vapor bands EXCLUDING the 2 main CO2 bands. So, what are you measuring when you use one of these toys?!?!?! NOTHING USEFUL IN THIS DISCUSSION!!!!

    I had a guy trying to tell me he was measuring close to the theoretical numbers. HOW?!?!?!?!

    Dr. Roy tries to use it to PROVE backradiation. So far I have never seen ANY paper that actually PROVES that water vapor and CO2 are what is causing all the radiation being measured by the pyrgeometers. How could they when they aren’t even measuring the same bands?!?!?! Logically there would not appear to be any other sources than the GHG’s in the atmosphere, but, that is not PROOF!!

    Yes they are measuring SOMETHING. WHAT and how much?!?!?!!?!?

    A couple other requirements for S-B to be accurate is a temperature equilibrium and the material being measured not being self irradiating. Umm, nothing we measure in reality is in equilibrium so there will be error. I assume this is the flux issue. The manufacturers claim you need back to back pyrgeometers to correctly compute the flux. The self irradiating part is also a hoot. The atmosphere is nothing but self irradiating. Remember the stuff about absorption and reemission until the IR gets out to space?? Isn’t that self irradiation?? The surface is irregular so is also often self irradiating!! Sorry, until there is some real work on this the numbers are fatuous. They could be right and we simply would not know it because of all the JUNK SCIENCE they have piled up.

    I would appreciate feedback on where I am going wrong.

  17. kuhnkat says:

    Big OOOPS!!

    I am writing pyrgeometer and several of my complaints are only appropriate for the IR thermometers with limited bandwidth. Some of what I wrote applies to the use of the pyrgeometers, but, not all.

    [mod: I’ve added a note, guessing where you had a spot of excess, don’t see it as a problems –Tim]

  18. AlecM says:

    @David Socrates: I am using standard physics with Trenberth;s data but I ignore the ‘333 W/m^2 ‘back radiation”, a paper energy flow. I also ignore Kirchhoff’s Law of Radiation applied at ToA – it is wrong. The energy flows then balance exactly, 238.5 in, 238.5 out.

    Hence the climate models claim 6.85 times as much absorbed surface IR compared with reality. This gives a perpetual motion machine. it’s why they went wrong and predicted imaginary positive feedback. Perhaps that was always the intention, perhaps it’s a cock up.

    In reply to kuhnkat,Thank you for the info about the models and their use of incorrect emissivity. This is the key to the bad mistakes in the modelling. The emissivity of the clear atmosphere is lower than pyrgeometers measure and it is semi-transparent so a pyrgeometer works partially by internal convection.

    The only real way to do the modelling is a wavelength by wavelength calculation. MODTRAN does this anyway and gives the predicted irradiance, the Planck Irradiation Function convolved with emissivity. Take up and down away and you get the net IR energy flux as a function of wavelength. The integral of that over all wavelengths is the total IR flux. You can have zero net flux but with part going one way and part the other. On top of this, most energy flux is convective and evapo-transpiration.

    The real fun is Pierrehumberts ‘CO2 dip’ in OLR, a very plausible explanation. You overcome this by invoking the IR optical behaviour of clouds which frequency converts CO2 IR to other bands. The Earth’s climate control system can easily cope with extra CO2 because it appears to have been designed that way. Over to you Roy!

  19. kuhnkat says, April 23, 2013 at 4:59 am and at 5:12 am

    I agree with your comment about IR thermometers. I have one myself. All it can do is to give a general indication of what is going on. Nevertheless I find it very useful in confirming that clouds do indeed radiate significantly downwards, apparently behaving as near black bodies.

    But the professional pyrgeometers such as the Kipp & Zonen CGR4 installed in dozens of meteorological centres all over the world (including Chilbolton) do appear to give readings across the LWIR spectrum that are broadly consistent with Trenberth’s 333Wm-2 estimate.

    For example the table on page 28 in the Kipp & Zonen CGR4 Manual (click in the Related Downloads section at the above link) shows, for clear skies, some typical readings: a minimum of 230Wm-2 downwelling radiation when the surface air is -20degC; 315Wm-2 when the surface air temperature is 0 degC; and 480Wm-2 when the surface air temperature is 30degC.

    What do I mean by “broadly consistent”? I mean of the “same order of magnitude”, as opposed to the ZERO value that some people claim it should be!

    So unless (as some people apparently do) one assumes that manufacturers of professional pyrgeometers are all in league with the devil (Trenberth perhaps? :-)), the simplest non-conspiratorial conclusion is that professional pyrgeometers: (i) do work well (Kipp & Zonen claim 5% accuracy for their CG4); and (ii) do record real downward radiation.

    Unlike Dr Roy, I am a hardline skeptic. Nevertheless I find it easy to accept the reality of back radiation without falling into the trap of thinking that its existence in some way proves the warmist (or luke warmist) case that GHGs cause additional atmospheric warming.

    It does not, because energy flow re-direction is not an energy storage process.

    The true cause of atmospheric warming is due to a build-up of kinetic energy (heat) in the material substances of the atmosphere (all the gases, GHG and non-GHG alike) due to the resistance that they collectively present to the net upward flow of energy as it passes through on its way back to space. Simple as that.

  20. donald penman says:

    I think that the temperature reading of the target depends on the distance it is from the pyrgeometer, the sensor will measure a larger exchange in ir radiation if it is closer to the target than if it is further away.The pyrgeometer takes distance of the target from the sensor into account indirectly,in the manuals it says the target should fill the viewing lens of the pyrgeometer. I did an experiment when i was with the Open University,a long time ago, where I estimated the distance to the moon using a ten pence piece and a ruler where I moved the ten pence piece along the ruler until it eclipsed the moon .Using right hand triangle theorems it gave an estimate of distance perhaps the pyrgeometer is using the same method.

  21. RACookPE1978 says:

    OK, but let me challenge the above “theoretical” comments about radiation heat losses with two, let us say, “practical exercises” with real world numbers.

    Open water at 3 deg C (276 deg K), wind speed <2 meters/sec, 1 meter air temp = -5 deg C (268 K), clear "night sky" at ????? deg C (-31 C as in the above sample ??, or -40 deg C in troposphere, or -273 C as if it were open space?). I can calculate how much is lost from the water by conduction and convection into the moving air, by evaporation. But how much is lost by radiation?
    Water is a flat "grey" body, but its emissivity is known: 0.963
    What is correct for "air" in this case?
    Absorbed (inbound radiation) would only be from the night sky in this case, right?

    Similar problem, but a cloudy night with ice-covered water.
    Air temp's and "sky" temperatures wold have to be the same as above.
    Emissivity of the clouds changes though, right?
    Emissivity of ice is almost exactly the same as water, ….
    But the "effective" radiating temperature of the top of the ice is now the 1 meter air temperature – much lower than the top-of-water temperature above – so the amount of energy lost when ice covers the same body of water at the same air temperatures under the same weather conditions is significantly less than when no ice is present?
    so amount of energy lost .

  22. Roger Clague says:

    The Kipp and Zonen pyrgeometer is designed for the solar power businesses. It is not designed for climate science research.
    The energy budget diagram in their solar energy guide does not include back radiation, as is the case with many other energy budget diagrams.

    David Socrates says

    the trap of thinking that its [ back radiation] existence in some way proves the warmist (or luke warmist) case

    The important thing to me is understanding the science regardless of which side of the debate it supports. I am always prepared and happy to change my opinion. I could become a warmist if they have the evidence and a credible theory

  23. Trick says:

    kuhnkat 4:59am: “I would appreciate feedback on where I am going wrong.”

    Few things:

    • TFK2009 uses 0.793 for the global atm. emissivity not as you write “very close to 1”.
    • Rounding water’s emissivity ~0.96 up to 1.0 saves a lot of unnecessary complications. This rounding is close enough for engineering work but granted maybe not for some specific science research.
    • Texts inform how expert specialists measure the emissivity of the atm. around 0.7 in dry arctic regions and 0.95 in humid tropics. Would make sense the global avg. atm. emissivity is in between.

    ******

    Roger Clague 12:55pm: “Kipp and Zonen pyrgeometer is designed for the solar power businesses.”

    The Kipp and Zonen pyranometer is designed for solar power business. From their solar energy guide, where the LW DWIR spectral response is clearly shown 4micron to 50micron so it IS included:

    “The ‘global’ short-wave radiation is measured by a horizontally mounted Kipp & Zonen CMP Pyranometer and the long-wave radiation by a Kipp & Zonen CGR Pyrgeometer.”

    http://www.kippzonen.com/data/uploads/download/KippZonen_Solar_Energy_Applications_Brochure.pdf

    ******

    AlecM 9:29am: “@David Socrates: I am using standard physics with Trenberth;s data but I ignore the ’333 W/m^2 ‘back radiation”, a paper energy flow.”

    It should be instructive for you to look at the components of the TFK2009 333 emitted to surface by atm. after having been absorbed by atm., none of which are just on paper, all of which are physical and have been measured reasonably well by specialist engineers as discussed from various science sources documented in TFK2009.

    17 thermals
    80 evapo-transpiration
    78 incoming solar absorbed by atm. (some overlap of spectrum)
    157 atmosphere gases having Tavg. > 0
    1 absorbed, missing, rounded, call it what you will.

    333 total LW DWIR LTE W/m^2 balance (March 2000 to May 2004) spatial and temporal sampled as reported by TFK2009 and roughly measured in real time day/night by many & various source’s instrumentation in place.

  24. Trick says, April 23, 2013 at 2:21 pm

    It give me great pleasure to say I am in 100% agreement with you. Thanks for your very clear and concise responses. It saved me a deal of writing.

    A small point on the emissivity of the atmosphere: I calculated a figure of 0.86 for my ATE Part I article assuming a temperature at the base of the atmosphere of 287K, just 2 degrees cooler than the surface at 289K. If I had used Trenberth’s emissivity figure of 0.793 (which at the time I didn’t know), the corresponding temperature would have been 293K, which would have been 4 degrees warmer than his 289K surface temperature! Interesting. I wonder how Trenberth squares that.

  25. Trick says:

    David 2:49pm: I gotta’ run, double check your work input on the solar side (~240 W/m^2) and compare to TFK2009. IIRC we discussed differences in the two in the past, that may resolve your issue given the ^4th power leverage.

  26. tchannon says:

    It’s a crude device, dumb. The field of view needs filling during test.

    It is supposed to be whole sky (“Field of view 180 °”), which poses a few problems.

    One is what if it can see an object which is not sky? There is no magic method other than a human looking. Wonder how the Davos lot get around mountains in field of view? (insert standard answer)
    Or more locally rather large radar dishes.
    I doubt this stuff is accurate enough for it to matter, still ought to be right though.

    I suggest a wide field of view is inviting claptrap figures, if it can “see” 50km away where *ground* conditions are different, wrong. It’s about here, not there.

    There might be enough data now to figure out the response but I see other things as more important and much easier.

  27. Trick,

    The relevant figure to use is the 333Wm-2 output radiation from the atmosphere downwards. With emissivity of 0.793, S-B equation then gives 293K as the atmosphere’s effective radiating temperature. But because the atmosphere is a 3-D ‘surface’ (!!), maybe that effective radiating temperature is some way up from the actual surface – say for the sake of argument at 900m. In which case, at a lapse rate of 6.5K/km, the surface it would be about…er…6K cooler, namely 287K.

    Just a thought… 🙂

  28. tchannon says, April 23, 2013 at 3:21 pm: I suggest a wide field of view is inviting claptrap figures

    Hi Tim,

    First of all, one can’t assume that organisations that run meteorological stations are incompetent. Do we know that they prone to placing their equipment in the middle of valleys, or woods, or even down mineshafts. 🙂

    Secondly, one can’t assume that pyrgeometer manufacturers like Kipp & Zonen are incompetent. As I understand it (and I may be wrong over this – I haven’t checked), although the professional pyrgeometers have a 180 degree field of view, the sensor inside is flat and facing directly upwards. So incoming radiation from oblique angles will be subject to the usual cosine rule of attenuation. In effect mainly the downwelling component is captured.

    If you are still worried you could easily research both these points.

    But until I hear to the contrary I, personally, will continue to make the working assumption that these devices, as installed all around the world, are providing reasonably accurate results. Remember the debate is not really over the last decimal place of accuracy. With many people the issue apperars to be whether these devices work at all!

  29. KuhnKat says:

    Any chance of your pointing this out in the paper or the additional info? I only see totals in the paper, not how he computed them. His first paper used 1. The numbers on the second and later being so close I would be interested in how he managed to use .79 for the atmosphere and still confirm his earlier work so closely.

    I would also be very interested in the papers measuring the emissivity of the atmosphere. In a very humid environment I can see higher emissivities similar to having cloud cover dramatically changing the situation. The upper atmosphere simply does not have moisture so will NOT have higher emissivity. As we are considering the overall emissivity from ground to space the fact that near ground level emissivity is high simply papers over the issue doesn’t it??

  30. Trick says:

    David 3:51pm: “So incoming radiation from oblique angles will be subject to the usual cosine rule of attenuation.”

    Certainly the solar incoming radiation is subject to the cosine rule where the sun feels like higher radiation on our bodies at zenith vs. near sunset. The pyrgeometer though views ~180 degrees as does its sensor from a “downwelling” bath – that’s why they use downwelling term not just “down”. The context of your comment seems to indicate you think of DWIR as from the zenith vector, it is not, it is a bath coming from nearby the view of the device.

    I will look up TFK97, compare TFK09 numbers and do the math showing kuhnkat 4:14pm (remember the instrument observes DWIR bath from close by, say much .LT. ~ 1km) how the global spatial and temporal atm. emissivity differ in the 2 papers; IIRC it WAS a little higher in ’97 but not near 1.0. To find it, you have to solve 1 eqn. with 1 unknown, which you linear algebra enthusiasts will recognize as uniquely solvable. Remember also the sampled time periods for satellite et. al. avg. observations will differ and the emissivity difference will be at least partly natural.

    This will take some time, day or two, I have a sporting event to attend today; not that around here isn’t good sport but there are other things – college ice hockey season is over now in NH & softball is going strong.

  31. Trick says:

    David 3:25pm: Something to consider in working your comment. The 333 total isn’t all useful for balancing the diabatic loop and obtaining your computed 293K, some of it is adiabatic loop (Stephen W. term — the 17 + 80) that just runs around doing pushups (MaxTM term).

    The 157 is the important diabatic number for global surface temperature (~288K) balance, you will see that 157 number (have seen that number) in the eqn.s for kuhnkat I’ll do later.

  32. tjfolkerts says:

    Trick, I have been agreeing with most of what you have said, but David is right that the angle matters. A cloud covering 20 % of the sky near the zenith will have a bigger impact than a similar cloud near the horizon since the detector is a horizontal sheet.

  33. kuhnkat says:

    Trick,

    Thanks for the time.

    Here is where I got my information:

    http://mc-computing.com/qs/Global_Warming/EPA_Comments/Trenberth.doc

    “According to Kiehl and Trenberth (1997), the outgoing longwave flux was measured by the ERBE satellite as 235 W/m2. The 78 W/m2 of latent heat is computed from the estimated global precipitation (rain and snow). The 67 W/m2 shown as absorbed in the atmosphere may actually be as high as 85 W/m2.

    The downward flux of 324 W/m2 is specifically for cloudy days, it is 278 W/m2 for clear days. However, the text also says that the clear sky longwave forcing is only 125 W/m2, 155 W/m2 on cloudy days.

    The rest of the values are assumed, estimated, or modeled. For instance, the 390 W/m2 from the surface is computed (not measured) assuming a temperature of 15°C and an emissivity of 1.”

    Apparently I screwed up and conflated the explicit emissivity of 1 for up with the figure not mentioned for down. Interesting that he states the test has other numbers for down besides what is shown in the figure. I would have thought the figure was the average, but, he states it is for cloudy!!

    So to compute the emissivity what temperature will you use, clear sky, cloudy, some average…

  34. Trick says:

    Tim F. 11:13pm – I can’t add much; it does seem what you set up is intuitive for a pyranometer (because we can see and feel sun/clouds!), but not necessarily so intuitive for a local more opaque source diffuse bath observed in the pyrgeometer view (which our lying eyes can’t see). Mean free path and all that.

    The specialists working with & calibrating the beasts would be the ones to ask, or sit with your computer display next to one and see how the various passing cloud set ups at different heights affect the readout.

    For all Tim C.s work on the Chilbolton data, maybe he’s interested in stopping by the place and asking someone these questions about the beast they use or e-mailing them. As I’ve written before, I bet they talk your ear off about the weird things they find prygeometers doing.

    ******

    kuhnkat 1:55am: “So to compute the emissivity what temperature will you use, clear sky, cloudy, some average…”

    The global avg. T over the temporal and spatial sampling period in ’97 and ’09, so to back out a global avg. emissivity computation. Doesn’t take long to do, just need look up a few scalar numbers from each paper and plug into the basic 1st law heat eqn. balance (e.g. the one from Bohren 2006 text p. 33 IIRC and other texts show same eqn.) and solve for unknown avg. atm. emissivity.

    In ’09, pretty sure they talk about rounding to 1.0 for L&O emissivity as you write; I need to double check ’97 to see if rounding up surface to 1.0 was in vogue then too.

    ******

    I had a few minutes extra here to chime in b/c the softball team I follow mercied the competition so game was shortened but then lengthened by rain delay; all you nascent meteorologists here need to realize softball games attract rain clouds. Let me know when you figure why THAT is.

  35. kuhnkat says:

    While you are toiling away Trick, thought you might be interested in this article:

    http://www.xylenepower.com/Emissivity.htm

    The one that computes the emissivity of the earth from space using observations from a Mars probe enroute.

  36. Trick,

    With all due respect to you and Kuhnkat, I think that you may be about to inadvertently hijack this thread – which is about pyrgeometers and not about the hotly disputed Trenberth’s figures which we have done to death already elsewhere.

    It’s up to Tim C of course as to how much he lets us stray off-topic. But as far as I am concerned, I use the Trenberth 2009 figures (as I have said many times before) simply as a ‘placeholder’ for discussion and will continue to do so until somebody comes up with plausible, and significantly different ones.

    So, personally, I am really not very interested in debating whether 333Wm-2 is exactly right – only concerned to establish some common sense, namely that:

    (i) Downward radiation from the atmosphere to surface exists and, on average across the earth’s surface, is around the 300Wm-2 mark, i.e. not ZERO as some claim!

    (ii) Pyrgeometers do measure the downward radiation reasonably accurately, say to within 5% (Kip & Zonen’s specification).

    Those who argue against (i) are either ignorant of the science (because it is well understood that water molecules and CO2 molecules at earth atmosphere temperatures radiate in the LWIR in all directions); or they are overly-bright physicist-philosophers who argue that only the net radiation of 23Wm-2 upwards should be considered as real, being composed of two ficticious numbers, upwelling radiation (356Wm-2) and downwelling radiation (333Wm-2) which nevertheless exist just sufficiently to enable one to do the subtraction, but then afterwards mysteriously vanish away. Fine – if you like that sort of sophistic argument. It’s no odder than quantum theory. It’s just not one that appeals to this down-to-earth engineer. 🙂

    Those who argue against (ii) need to support their arguments with proper proof that professional pyrgeometers such as the Kipp & Zonen device are not appropriate or reliable instruments. So far, that proof has not been forthcoming, either here or on the previous lengthy pyrgeometer thread – just a lot of arm waving from people, most of whom don’t seem to know an awful lot about them.

  37. AlecM says:

    Trick says:
    April 23, 2013 at 2:21 pm : ‘333 total LW DWIR LTE W/m^2 balance (March 2000 to May 2004) spatial and temporal sampled as reported by TFK2009 and roughly measured in real time day/night by many & various source’s instrumentation in place.’

    I do not dispute that this is the output of the instrument. However it is not a real energy flux, but the potential energy flux from an emitter at the measured temperature to a sink at absolute zero. This is because it is calculated by the S-B equation from the measured temperature. To get the real flux, you need the 2nd S-B equation.

    396 W/m^2 potential flux from a black body at 16 °C minus 333 W/m^2 potential flux from the atmosphere = 63 W/m^2 comprising 23 W/m^2 absorbed in the atmosphere by non self-absorbed GHGs and 40 W/m^ 2 to space, the experimental values. You can’t mix real energy fluxes and potential energy fluxes. Meteorologists are taught ‘back radiation’. Physicists and engineers are not: they are taught to use the difference signal.

    The 333 is not real, neither is the 396. Therefore the real warming has been exaggerated by G= 396 – 238.5 = 157.5/23 = 6.85. The extra heating is then offset in hind casting by extra cloud albedo based on Sagan’s incorrect aerosol optical physics.

  38. Bryan says:

    Can David Socrates read?

    David says

    “Those who argue against (ii) need to support their arguments with proper proof that professional pyrgeometers such as the Kipp & Zonen device are not appropriate or reliable instruments. So far, that proof has not been forthcoming, either here or on the previous lengthy pyrgeometer thread – just a lot of arm waving from people, most of whom don’t seem to know an awful lot about them.”

    ……
    “Pyrgeometers do measure the downward radiation reasonably accurately, say to within 5% (Kip & Zonen’s specification).”

    http://www.webpages.uidaho.edu/~vonw/pubs/TownEtAl_2005.pdf

    Users report 8% uncertainty

    http://www.arm.gov/publications/proceedings/conf16/extended_abs/stoffel_t.pdf

    On page one they report persistent uncertainty under clear sky condition of (-12 + or – 5)W/m^2.

    So a reading of 100 could really be anywhere between 83 and 93W/m^2 .
    This article also suggests that the calibration equation used by manufacturers is wrong and comes up with their own alternative.

    Both these articles are written by professional scientists and are the most recent I can find.

    Both these papers have been linked in threads where David participated.
    Perhaps he has not bothered to read them?

    David has yet to produce his own evidence from users to support his 5% figure.

  39. Trick says:

    AlecM 2:49pm: “I do not dispute that this is the output of the instrument.”

    The 333 gross LW DWIR LTE W/m^2 you refer in your clip is NOT the output of a pyrgeometer instrument though one can use the instrument to observe nature’s DWIR bath. The gross 333 DWIR components are from physically observed real natural earth processes as I listed for you above 4/23 2:21pm.

    Consider the 333 component of 80 from evapo-transpiration for example. This number results in part from actual observations of measured rain amounts and river runoffs throughout the world. And so on down the list, from actual specialist physicists and engineers. Do you dispute that these components making up the 333 are not real?

    Specifically, the 333 IS roughly rainfall et. al. physical reality (and not any sort of potential) during the CERES measurement period March 2000 to May 2004. Just look around you when it is raining to observe & feel part of the global 80 component. Observe the transpiration of yourself and vegetation around you for the rest. Better to be roughly right than precisely wrong (hint for Bryan).

    The net DWIR 157 is not exaggerated real warming (AlecM term) at all, it computes out to Teq.=~289K for the near surface global atm. temperature which is remarkably close (text book example) to thermometer measured Tavg. = ~288K. I’ll post that when I finish my simple, basic research answering kuhnkat.

    ******

    David 9:37am: I am not sure what you consider off topic by your comment. This thread is a discussion of pyrgeometer’s IR measurement. That IR is emitted as gross DWIR from the atm., components of which are physically real. Logic then shows concept of global atm. emissivity as a real component is worth discussing. Logically Trenberthian figures for nature’s observed gross DWIR 333 are a target to frame the pyrgeometer IR measurement for comparison and thus logically on topic IMO.

    Ok, maybe softball games attracting rain clouds does stretch it a bit, I agree humor is off topic, it uncontrollably leaks out of me sometimes. But it’s like a cocktail party atm. around here, can just move along to the next conversation.

    ******

    kuhnkat 5:20am: I looked thru your link. It is a snapshot of OLR in one earth scene on 11/23/1996. The process they go thru to compute emissivity and temperature at one instant in time & 1 scene is likely similar to the data reduction from CERES gazillion snapshots of scenes in much longer measurement period to arrive at a spatial and temporal annual avg. as reported in TFK09 and the ERBE 5yr. window mid-1980s in KT97.

  40. Bryan says:

    The Kipp & Zonen pyrgeometer linked above has no battery or external power supply.
    The energy to output a reading must come from the voltage developed across the thermopile.
    When pointed to a cold sky from a warmer Earth surface this is indicating the heat flow FROM the pyrgeometer TO the colder sky.

    This is the only REAL physical reading available.

    Now taking this real measurement and combining it with SB equation and the known temperature of the pyrgeometer we can make a guess as to the backradiation.
    The Stoffel paper linked above fine tunes this approach attempting a more accurate guess.

    The results are then conveyed to the public in such away as to convince them that the cold night sky heats or warms the warmer Earth surface.
    Anyone who has studied the Carnot Cycle approach to the Second Law of Thermo realises that this is impossible.
    What is happening is more accurately described as radiative insulation .

  41. tchannon says:

    David, threads have lives of their own. I went to the trouble, takes several hours with preparation, to do a double article, then published rapid fire one two. Done to keep likely side issues off the important article, which is supply of data. This thread is the victim for any excessive talk,

    There is a call on what are topics. In this case chipping away getting closer to some core matter which brings lots of talk, I’m doing to try and shine light without really caring where the slender thread of enlightenment leads or breaks. Many little details will be turning up.

    Rog was good enough to hold off posting articles for a day or so, giving more exposure. Fortunately blog visits held up, few comments though.

    We are trying (not planned) to do a blog which has a mix.

  42. Tim Folkerts says:

    AlecM says: ” Physicists and engineers are not: they are taught to use the difference signal.”

    No. As a physicist, I can assure you we are taught BOTH — and we use either as the case warrants. For example, when there is a gentle breeze blowing, I am perfectly happy to say the AVERAGE speed might be 1 m/s, while at the same time acknowledging that some air molecules are heading the opposite direction at several 100 m/s.

    You seem to disagree with the wave-particle duality idea, since you don’t “believe” in photons simultaneously going both directions. But that puts you ~ 100 years behind the times, and makes some experiments impossible to explain. There is no “bad physics” involved in saying that 396 J of photons are heading up from each square meter of surface each second, AND that 333 J of photons are heading down toward each square meter of surface each second. They are not “potential photons” or “virtual photons” — they are real photons.

    Or to use a different analogy, if I give you $100 and you give me $90, then I really did give you $100, but the net exchange is $10. Both the $100 value and the $10 value are “real” and each has its own meaning. (For example, you might get taxed on the gross income of $100, or you might only get taxed on the net income of $10.)

    But this is all semantics. Or it is philosophy as pointed out by David earlier. It makes no practical difference if you say that 396 goes up and 333 goes down, or that 63 goes up. The temperature of the earth is the same either way. The impact of the CO2 is the same either way. The radiation to space is the same either way.

  43. Trick says:

    KuhnKat 4/23 4:14pm: “I would be interested in how he managed to use .79 for the atmosphere..”

    I was too. KT97 and TFK09 both support it is reasonable to make L&O emissivity = 1.0, rounded up slightly. Both papers discuss emissivity of components of the atm. like clouds. Neither talk about bulk atm. emissivity in the common text book sense and the pyrgeometer or IRT measures locally. Up to the reader to figure it out, I did so using L&O = 1.0 rounded up slightly for simplicity.

    I started with simple, basic atm. text energy balance equation at surface from say Bohren 2006 p. 33 plugging in their data:

    Gross solar input = 1370 W/m^2
    albedo=0.7
    surface emissivity=1.0
    atm. emissivity =0.8/2 because atm. radiates half up & half down equally.

    Plug into their balance equation:

    (1370 * 0.7)/4 – sigma*(1-0.8/2) * Teq. avg. ^4 = 0

    Solve in Excel say for Teq. avg. atm. near surface = 289.7K

    239.5 – (400-160.5) = 0, so balances and Teq. within 1K of recent surface thermometer
    Tavg.=~288K

    Observe this is net solar in – (net UWIR – net DWIR) out = 0. Then change over to TFK09 numbers in Excel, get the 157 net DWIR component from my 4/23 2:21pm listing, the net UWIR = 396 is done for you in the cartoon:

    239 – (396 – 157) = 0 so iterate the excel spreadsheet numbers to find Trenberthian09 atm. emissivity balanced solution:

    (1365.7 * 0.7)/4 – sigma*(1-0.793/2) * Teq. avg. ^4 = 0

    Solved for Teq. avg. atm. near surface = 289.1K at Trenberthian global atm. emissivity of 0.793 compare to 1961-1990 thermometer measured 287.0K mentioned in paper. Not too shabby.

    ******

    For KT97 cartoon numbers, have to first find the net DWIR, once again the net UWIR = 390 is done for you:

    24 thermals
    78 evapo-transpiration
    67 incoming solar absorbed by atm. (some overlap of spectrum)
    155 atmosphere gases having Tavg. > 0
    +0 absorbed, missing, rounded, call it what you will.

    =324 total LW DWIR LTE W/m^2 balance (5yr. mid-1980s ERBE) spatial and temporal sampled as reported by KT97. Thus net DWIR is 155 relevant component of the 324 shown in KT97 cartoon. Which becomes in balance eqn.:

    235 – (390 – 155) = 0

    Iteratively solve Excel to match this balance, find Teq. avg. atm. near surface = 288K at global atm. emissivity of 0.795.

    (1342.9 * 0.7)/4 – sigma*(1-0.795/2) * Teq. avg. ^4 = 0

    So I find Trenberthian bulk global atm. emissivity over 2 different measurement periods to be .793 and .795 not significantly different from text book data rounded to 0.8. YMMV, some rounding, confidence intervals and typo. issues excluded. Seems like I did this before, wonder if it came out the same, LOL, I didn’t make the effort to look it up.

    KuhnKat continues: “I would also be very interested in the papers measuring the emissivity of the atmosphere.”

    IIRC there is a terrific discussion in Bohren 1998 text. Possibly the Bohren 2006 text.

  44. wayne says:

    Trick, that’s one large amount of words and equations for merely saying the whole Earth emissivity according to TKF is ε ~= 0.603 (in your equation it is (1 − 0.794 / 2). So what is your point?

    We already know they say 238.5 / 396 = 0.6022 = your (1 − 0.795 / 2)

  45. Tim Folkerts says April 24, 2013 at 7:46 pm

    Tim,

    Yours is the best rational analysis of this silly dispute so far. Although you and I are on opposing sides of the fence in the great climate debate, we don’t flinch from agreeing where common sense dictates that we should. This whole debate about back radiation is a nonsense because, as you say, the net figure is the same in the end anyway – a flow of energy from cooler to warmer, not in violation of the 2LT.

    It seems that skeptics have a visceral hatred of the concept of back radiation because they think it lends credance to the idea that the back radiation causes warming and therefore confirms the warmist position. That is the gist of Brian’s comment above (April 24, 2013 at 5:09 pm ) where he says “The results are then conveyed to the public in such away as to convince them that the cold night sky heats or warms the warmer Earth surface.”

    He and others cannot see that back radiation actually has nothing whatsoever to do with the discussion about whether or not radiative gases in the atmosphere cause surface warming. As you and I have discussed many times, that question is a matter of resolving whether the warming mechanism is to do with Throughput Throttling or Output Throttling. In all the heated discussions you and I have had on that substantive issue, I do not recall either of us ever mentioning back radiation.

  46. Oops…”cooler to warmer, not in violation of the 2LT” should of course read “warmer to cooler, not in violation of the 2LT…” It’s getting late. 🙂

  47. Bryan says:

    What David Socrates says above at April 24, 2013 at 9:37 is classic pot and kettle black comparison

    “Trick,

    With all due respect to you and Kuhnkat, I think that you may be about to inadvertently hijack this thread – which is about pyrgeometers and not about the hotly disputed Trenberth’s figures which we have done to death already elsewhere.”

    David then outdoes Trick and Kuhnkat by a mile with a blatant return to the tired arguments of the previous thread.

    tchannon has put a lot of work into this post and I for one was hoping for more detail would emerge.
    For instance can anyone suggest a way to independently check that a reading of say 100W/m^2 is accurate by an alternative method that does not use the same equations as used to calibrate the pyrgeometer.
    The problem of circular logic could then be avoided.

  48. Trick says:

    wayne 10:32pm – “So what is your point?”

    • LOL, NOW you tell me, why not say that before; it does show how the components of the 333 physically work inside your ratio resulting in surface temperatures from 1st principle,
    • Pyrgeometer looking up doesn’t see the whole earth emissivity
    • discussing with kuhnkat how the atm. emissivity is less than 1
    • was interesting to find out if KT97 led to a different atm. emissivity component from a period ~15 years earlier than TFK09 complete with temperatures, note the small increase 288K to 289.1K while atm. emissivity decreases very slightly, that alone should be interesting, might be a rounding issue or can pyrgeometer records at Chilbolton or anywhere confirm? How long are they?
    • Support that the 333, 396 TFK09 flows are not just potential flux but real, useful & observed for AlecM; and that there is no 6.85 factor to worry about
    • For me, it helps show how the emissivity of the atm. affects surface temperature, can quickly run the true numbers, see how they basically work, when some poster says “this” happens if you do “that”.

  49. tchannon says:

    I can run through simple days of data where something basic is happening, showing the different changes, what to look at.

    Would this help?

    If so, in-line in comments or a new article? (the latter is easier for images, a few posts will not trouble Rog)

    A candidate is 27th Feb when dense cloud clears at abt 15 hours, a rare day when there is radar too. Nothing complex is happening.

    I’m intending doing the more interesting details at some point, for example, where solar input is in excess of the maximum. Not obvious this happens but this confirms what I came across elsewhere, rather showing how things are more complex than is plain.
    (wondering? More than one sun, optical effect of some cloud)

  50. kuhnkat says:

    Trick,

    “It is a snapshot of OLR in one earth scene on 11/23/1996. The process they go thru to compute emissivity and temperature at one instant in time & 1 scene is likely similar to the data reduction from CERES gazillion snapshots of scenes in much longer measurement period to arrive at a spatial and temporal annual avg. as reported in TFK09 and the ERBE 5yr. window mid-1980s in KT97.”

    Yes, it is a snapshot of the earth centered over the Pacific ocean close to Hawaii.

    What I am reaching for, and maybe you can actually pound into my head. is why this snapshot of the WHOLE earth is about .75 when the atmospheric sensitivity WITHOUT the earth backing is said to be about .79. The snapshot would seem to imply to me that the atmospheric emissivity, that is without the ocean and earth adding in frequencies and amplitude, to be smaller??

    David Socrates,

    any idea on proving that it is the GHG’s which are the source of all the radiation coming from the atmosphere??

    Any feedback on my suggestions that S-B is being used incorrectly in the computations leaving an error that is not being accounted for??

  51. KuhnKat says:

    Trick,

    probably not a big issue, BUT, this has always irritated me:

    “atm. emissivity =0.8/2 because atm. radiates half up & half down equally”

    NOPE. Just look at the geometry. What a particle “sees” is a cone that can be irradiated which will reach the earth. The higher the particle the smaller the angle at the apex of the cone and therefore the smaller the percentage of radiation that actually goes earthwards!!!

  52. kuhnkat says, April 25, 2013 at 4:39 am

    You ask: any idea on proving that it is the GHG’s which are the source of all the radiation coming from the atmosphere??

    That’s a strange question and I’m not sure why you asked it. By definition, GHGs are those constituent atmospheric gases that radiate significantly at atmospheric temperatures, principally water vapour.

    You ask: Any feedback on my suggestions that S-B is being used incorrectly in the computations leaving an error that is not being accounted for??

    I have no feedback to give you. Remember that my interest is in whether professional pyrgeometers are accurate to within five or ten percent so I am not prepared to spend time on analysing instrument techology in any more detail than that. But if you are interested in challenging the 5% stated precision of the Kipp & Zonen CG4 pyrgeometer, I suggest you try challenging their technical department. Then you might get some really interesting and informed feedback from experts to help you understand the technology better.

  53. kuhnkat says:

    Then why are you here?? If you do not care how the instrument is used the acuracy is pointless.

  54. Trick says, April 25, 2013 at 12:12 am: …it helps show how the emissivity of the atm. affects surface temperature…

    We mustn’t forget that what we are talking about is an ‘effective emissivity’ computed backwards from the measured downwelling radiation. The latter is the important figure, not the former which is, of course, simply a mathematical artefact.

    The logic goes as follows:

    1. The atmosphere is heated by the Sun, both directly from incoming LWIR (78Wm-2), and indirectly via the upwelling energy from the earth’s surface, latent heat (80Wm-2), conduction/convection (17Wm-2) and net radiation (23Wm-2). In any case, it all ends up a kinetic energy (heat), even the 23wm-2 net upward radiation. It all heats the atmosphere.

    2. In proportion to the temperatures at various heights up the atmospheric column, the GHG molecules there (mainly water vapour) radiate. This radiation is a consequence of the temperature at each height and not its cause.

    3. Progressively closer to the ground, this emitted radiation from GHG molecules may reach the ground without being re-absorbed by other GHG molecules.

    4. Looking up from the surface, the pyrgeometer sees all the ‘downwelling’ flux that reaches the ground. The pyrgeometer doesn’t care whether an individual photon comes from 1km up or from 1m up. If that photon reaches the ground it is added to its energy count.

    5. Consequently, from the pyrgeometer’s perspective the atmosphere isn’t a 2-D surface at all but a 3-D volume that delivers a measurable flow of radiation.

    6. So the conversion of that radiation to a ‘temperature’ is not perhaps in this case a very useful exercise because the figure obtained is, as I suggested to you in an earlier comment, actually the temperature at an average ‘effective radiating height’ and not the temperature at the surface.

    So, given the above analysis, the important issue is that the pyrgeometer delivers for us a measure (to a degree of accuracy that we can argue about separately) of the energy flux arriving at the earth’s surface in watts per square metre. That’s what Chilbolton and the other meteorological centres round the world detect and publish. Not temperatures!

    So, although worrying about the ‘effective temperature’ of the atmosphere and its corresponding ‘effective emissivity’ is interesting intellectually, I suggest it is not really central to the issue of whether pyrgeometers deliver a reasonably accurate value in watts per square metre for downwelling radiation.

  55. Trick says:

    David 10:13am: “…an ‘effective emissivity’…which is, of course, simply a mathematical artefact.”

    Sent me over to dictionary.com. Artefact (or artifact) means a spurious experimental result. Spurious means not genuine, authentic, or true.

    I observe the interest in pyrgeometers arose around here and elsewhere to check the basic theory of atm. radiation is genuine, authentic and true against experimental results. Unsurprisingly, these results did turn out to support the basic, first course natural theory of atm. emissivity. Meaning the pyrgeometer instrumentation designs developed over time do reasonably detect the local amount of earth’s UWIR and DWIR predicted by the L&O and atm. emissivity theory.

    The preponderance of evidence then supports nature’s well mixed gaseous emissivity value found for the global atm. can be usefully used by scientists and engineers to work on understanding changes to the near surface global avg. atm. temperature from an atm. emissivity change (or L&O emissivity change). THAT is a work in progress.

    Understanding changes in nature’s atm. emissivity stuff as confirmed by pyrgeometer and thermometer instrumentation is important as you know since we live and cultivate crops in the near surface atm. temperature fields (not the “effective radiating height” which is mathematical). Tim C. is on the right track to inform on the work in progress at Chilbolton, on the surface.

    ******

    kuhnkat 4:39am: “…maybe you can actually pound into my head. is why this snapshot of the WHOLE earth is about .75 when the atmospheric sensitivity WITHOUT the earth backing is said to be about .79.”

    The emissivity computed in your link varies with scene changes, clouds, water, earth vegetation go by (same as pyrgeometer scene varies). Suppose a snapshot 12 hours later showed whole earth scene with atm. emissivity figured out to be 0.83. Then have two scenes which you can avg. to try and understand the globe atm. emissivity (.83 + .75)/2 = 0.79 and you would then look for changes to the global atm. emissivity value of .79 not the changing scene values.

    KuhnKat 6:24am: “What a particle “sees” is a cone…”

    Maybe so for a particle but the total radiation from a body comes from the surface of the body. We basically think of the atm. as one body with two surfaces (granted somewhat hard to exactly define) so each surface radiates the total/2. One surface of atm. body radiates total/2 to space, other one radiates total/2 to earth surface. 0.8/2 or 0.793/2 number in the balance eqn. comes from that basic construct.

  56. Trick says:

    Tim C. 2:33am: “I can run through simple days of data where something basic is happening, showing the different changes, what to look at. Would this help?

    Learning thru this thread, if I had my druthers the Chilbolton pyrgeometer days of data could be helpfully analyzed for any significant trending change in atm. emissivity, or more simply DWIR, that could be crossed checked with other data for correlations (water vapor, surface temperature, whatever interested in). Of course, those druthers add in statistical challenges.

    Tons of work. Need a NSF grant equipped w/grad. students. The grants seem to be irritatingly easy to get out of we taxpayers these days, LOL.

  57. Roger Clague says:

    David Socrates says:
    April 24, 2013 at 10:59 pm

    back radiation actually has nothing whatsoever to do with the discussion about whether or not radiative gases in the atmosphere cause surface warming.

    This discussion is about pyrgeometers and the claim they measure DLWR. That is back radiation.
    What are they measuring?

    From the figures on page 28 of the manual for the Kipp and Zonen pyrgeometer, it is the ambient temperature.

    I have looked at 30 earth energy budget diagrams. 2/3 of them include a big scary back radiation arrow ( usually red ), labelled CO2 greenhouse effect
    Back radiation is the main mechanism used to support the claim of trapping heat by CO2

    You have a more sophisticated theory of CO2 warming which we are not discussing in this thread.

  58. AlecM says:

    Trick 4.44 pm

    You can’t claim that the 80 W/m^2 evapo-transpiration energy is part of ‘back radiation’. It’s latent heat converted to convective energy when rain falls.

    I don’t know if you are trying to deceive yourself or me. The fact is, the 333 W.m^2 does not exist except as a reduction of the 396 W/m^2.that would be emitted from the surface if it were isolated in space.

    This is heat transfer lunacy.

  59. Trick says:

    AlecM 10:30pm: “…latent heat converted to convective energy when rain falls.”

    Yes, in part. Then what happens to that energy when the 80 disperses around atm.? Lost? Destroyed? Stored? No. Unless you claim it is then convected somehow outside earth/atm. system & just lost to that system, to space maybe? Not so. It stays (absorbed/emitted, conducted, convected) in the atm./surface adiabatic loop running up and down in circular balance returning as the 80 and 17 components of the total 333 observed in measurements from the dispersed pyrgeometer instruments.

    TOA radiative transfer out only as you know, no convective or evapo-transpiration transfer of energy gets to space besides what they contribute by radiative transfer to leave via the 239 OLR and return in balance w/surface as (80+17) real components of the gross 333 observed in the time period March 2000 to May 2004.

  60. tchannon says:

    I’ve decided to do a basic explanation clarifying reality. This won’t add anything for most readers on this thread but might be of wider interest.

  61. AlecM says:

    Trick 11.33 pm.

    The atmospheric control system operates to a simple set point. Energy IN = Energy OUT. It can cope with CO2 concentrations at least 12 times present levels without significant change of temperature at constant atmospheric mass and insolation. The water vapour level is roughly constant hence the stored latent heat is roughly constant.

    Of the 160 W/m^2 SW at the Earth’s surface, 17 is direct convection, 80 is latent heat and 63 IR with 40 of that direct to space, the 23 mainly heating clouds.

    The 333 is purely theoretical. No one has ever proved back radiation exists as a real energy flux. This year, 2nd year students at a Russell Group university physics course were told as an exercise by their exasperated prof to invent a reverse heat engine so you could power your car by a collector on the roof with all that free energy.

    Back radiation is a dead parrot, a Norwegian Blue, nailed to the perch by silly Climate Alchemists who imagine that the S-B equation predicts a stream of heat flowing to other bodies. It does not and the real volumetric heat flow is the negative of the difference of monochromatic radiative flux densities integrated over all wavelengths.

    The really clever Climate Alchemists pull out of the hat an FTIR spectrum of the sky and claim this is a direct measure of energy. It is not. it is the Planck Irradiation Function convolved with emissivity, the potential energy flow at each wave number/length to a sink at absolute zero. At the surface it is all destroyed leaving an effective surface emissivity of ~0.4, 1/3rd in water and trace gas side-band absorption, the rest to space.

    The proof that this is correct is to scale 0.4 by 63/160 = 0.1575, the average emissivity of the Earth. Then you compare this with the real experimental value = 63/396 = 0.159!

  62. Roger Clague says:

    AlecM says:
    April 26, 2013 at 9:38 am

    At the surface it is all destroyed leaving an effective surface emissivity of ~0.4, 1/3rd in water and trace gas side-band absorption, the rest to space.

    The proof that this is correct is to scale 0.4 by 63/160 = 0.1575, the average emissivity of the Earth. Then you compare this with the real experimental value = 63/396 = 0.159!

    I am also skeptical that pyrgeometers measure large, 200 to 500 Wm-2, downwards long-wave radiation energy transfer.
    .
    Please explain your alternative explanation, as above, more fully.

  63. Trick says:

    AlecM 9:38am: “The 333 is purely theoretical…”

    No, the atm. has real, physical IR emissions toward earth and space from each of its two surfaces since T>0. The 63 IR is net not gross; I listed the gross components for you above – all real and experimenatlly measured & easily physically observed just by walking around.

  64. tallbloke says:

    Trick: “emissions toward earth and space from each of its two surfaces”

    This is where we disagree. Downwelling radiation emanating from high in the atmosphere is reabsorbed within a short distance and the energy carrying gases are convected upwards again. The pyrgeometer on the ground measuring the downward part of the radiative flux is measuring radiation emitted almost totally from gases within a small range of altitude above it. So we’re not talking about ‘a surface’, radiating to space from one side and towards the ground from the other, but a body of gas close to the ground, which was warmed by the ground by conduction, via convection, and to a lesser extent by surface emission of radiation. Thus the radiative flux is mostly an effect not a cause. Trenberth claims 33C, a recent document I looked at claims 18C. I estimate 5-9C for the radiative greenhouse effect.

  65. […] Talkshop has several discussions to do with pyrgeometers, such as here, which has links to the Chilbolton data […]

  66. kuhnkat says:

    Trick,

    “Maybe so for a particle but the total radiation from a body comes from the surface of the body. We basically think of the atm. as one body with two surfaces (granted somewhat hard to exactly define) so each surface radiates the total/2. One surface of atm. body radiates total/2 to space, other one radiates total/2 to earth surface. 0.8/2 or 0.793/2 number in the balance eqn. comes from that basic construct.”

    Climate Science is very fond of AVERAGING things and the AVERAGE going down is less than 50%. Probably a small difference but when all those small differences just ignored are added up .9 w/m2 isn’t so big anymore!!

    I would also point out that those two surfaces are spheres. The lower surface has a self irradiating topology!!!

    My first post talked about one of the requirements of S-B use is that the topology of the object must be a configuration that does not allow self irradiation. The atmosphere obviously does NOT meet this qualification. So I would ask, what experimentation has been done to verify that these common practices actually come up with reasonable results. Sorry, I haven’t looked into the link you provided for atmospheric emissivity measurement, but, that would not actually explain this to me.

    Continuing on with the original question. I understand that different conditions will give different values for emissivity. For the whole earth number the actual emissions include radiation from the surface which would fill in holes in the emissions of the atmosphere. This would give a HIGHER emissivity than just the atmosphere. How can Trenberth be using an emissivity HIGHER than a whole earth emissivity for just atmosphere (the computed 333 DLR) when there is nothing behind the atmosphere to fill in those holes?!?!?!

  67. Trick says:

    tallbloke 6:07am: The satellites measure ~255K and the surface thermometers measure ~288K, spatial and temporal sampled March 2000 to May 2004. Those are the two surfaces that count. Neither surface self radiates. Call it what you will, there is nature’s 33K. Nothing fancy.

  68. kuhnkat says:

    Trick,

    the area radiating at the higher temp is SMALLER than the area radiating at the lower. Probably not as much difference as you think. Toss in a few other errors and ya got unity.

  69. Trick says:

    kuhnkat 7:07am: Not sure what you mean about area and temperatures if you refer my 6:57am post. For radiation flux density a m^2 is a m^2 in finding the 0.80 atm. emissivity is not 1.0 unity just from earth’s atm. Clear atm. has emissivity measured 0.7 in dry arctic and 0.95 humid tropics, m^2 for m^2. .

  70. KuhnKat says:

    Apologies for confusing the issue. I was referring to your response to TB where you said:

    The satellites measure ~255K and the surface thermometers measure ~288K, spatial and temporal sampled March 2000 to May 2004. Those are the two surfaces that count. Neither surface self radiates. Call it what you will, there is nature’s 33K. Nothing fancy.

    Those numbers are meaningless until converted to flux based on area or total energy transfer. It is like subtracting one orange from two apples. Gotta settle on what you are talking about and find the commonality to do the operation. Are you just talking numbers, two – one, with no real meaning or something physical, such as joules or w/m2??

    Again you throw the alledged measured numbers at me. Again I ask how can a whole earth measurement including ocean, clouds, atmosphere, land… be smaller than the measurement of atmosphere only???

  71. Trick says:

    kuhnkat 11:46pm: The 255K and 288K are in kelvin. Those are meaningful temperature numbers. Like apples and apples they can be differenced since on the same scale. They are 33K different. Very physical. Not at all alleged, they are observed & measured by instruments.

    I am not sure what you mean by last question, I detailed an answer to you above. The previous question was similar and interesting but I understood it better.

  72. KuhnKat says:

    Trick,

    are you stupid are just pulling my leg???

  73. tchannon says:

    Misunderstanding I think. The point is perhaps the numbers are dubious yet major errors seem unlikely, major say +-10K

    I’ve never looked at how the satellite measure is done, only so much I can handle. This may though rise up the interest stakes when I start thinking about clear sky.

  74. kuhnkat says:

    Trick,

    I want to apologize for my excessive reaction to your response. Let me try again.

    What temperature an object is only partly determines the amount of IR or energy it can emit/conduct. You can tell me something emits at 288k but that only gives me a w/m2 equivalent, it does not give me a quantity of IR or Joules.

    An object 1 square meter in surface area might be emitting at 333 w/m2. That is a relatively complete description as we know it is one square meter emitting so I think I can conclude it is emitting 333 w per time interval. You gave two temperatures which IMPLY the surface of the earth and the point at which the measurement is taken in space. Whether you claim that smaller number is taken somewhere within the atmosphere or at the instrument, the actual AREA emitting at that rate is larger than the surface of the earth. That immediately makes your direct comparison of the two numbers invalid without a transform adjusting for the different size of active emission. Since the actual emissive area is a VOLUME and not a surface you introduce further issues not easily handled and simply inappropriate for S-B computations.

    That single transform will not make the numbers equal, but, the difference is not as large as you imply and it still ignores other possible errors.

  75. kuhnkat says:

    Trick,

    April 23, 2013

    You claim the Pyranometer measures the IR band also. The link you provide does NOT state or show that.

    “The ‘global’ short-wave radiation is measured by a horizontally mounted Kipp & Zonen CMP Pyranometer and the long-wave radiation by a Kipp & Zonen CGR Pyrgeometer.”

    “Measurements of solar radiation are usually made using thermopile type radiometers with a flat spectral response. The types of instruments, performance specifications, and calibration methods are defined by the World Meteorological Organisation (WMO) and International Standards Organisation (ISO). They provide accurate measurements of the total solar energy available under all sky conditions. The data can be compared with measurements from meteorological networks and satellites, across various locations, and for dierent types of solar energy systems.”

    This does not sound like engineers setting standards. This sounds like Bureaucrats setting standards!!! At least they are CONSISTENT!!! By the way, that brochure listed standards for PV panels and Pyranometers, BUT, didn’t manage to reference one Pyrgeometer standard!!!

    Looking at other products I find a reference to track:

    http://www.hukseflux.com/product_group/solar-sensors

    Apparently the standards for pyrgeometers and IR is The Infrared Radiometry Section of the World Radiation Centre (WRC-IRS) at WISG,
    http://www.pmodwrc.ch/pmod.php?topic=irc
    Interesting stuff.

    It would appear calibration consists of comparing to the standard instrument at PMOD facility. To find out about the set up and operation of the standard you have to contact: julian.groebner(at)pmodwrc.ch
    http://www.pmodwrc.ch/pmod.php?topic=calibration#BM2__Calibration_of_Longwave_Radiometers

    I won’t be doing that. It might ruin my Conspiracy Theory about pyrgeometers!!