Guest Post by Willis Eschenbach
Since the late Nineties the US has had seven industrial-strength stations that measure a variety of climate variables every minute, 24/7. These are called “SURFRAD” stations. As a data junkie I’ve been wanting to look at their results for a while … but the data is in an ugly format. They have a single data file for each station for each day of the last 17 years … not my idea of a party.
Anyhow, I finally bit the bullet and downloaded a year’s worth of data, about a quarter of a gigabyte. For no particular reason I picked the SURFRAD station in Goodwin Creek, Mississippi, and the year of 2010. For each minute they have no less than 21 different measurements (see end notes) … so I sorta started digging around in the data to see what stuck out. Here was the first oddity I came across:
Figure 1. Average 10-metre surface air temperature (black, °C) and average downwelling infrared radiation (blue, W/m2) for the year 2010. Measured at the SURFRAD station in Goodwin Creek, Mississippi. Average covers the entire year, and is shown repeated twice (two days) for clarity.
I don’t know why, but I wasn’t exactly expecting that … which is the best part of science. I love surprises, the unexpected, and climate science is chock full of those. I mean, I knew that downwelling radiation was a function of air temperature … I just didn’t expect the alignment with the underlying surface temperature to be so exact. Other than the atmosphere starting to cool a bit earlier in the day than the ground (as we’d expect from the relative masses) they match up perfectly.
Now, seeing how good that match was, I got to wondering how well that fits the theoretical profile that we’d expect from the Stefan-Boltzmann (S-B) relationship. This relationship says that infrared radiation is equal to emissivity times the Boltzmann constant times the temperature to the fourth power. I figured that using that formula, I could calculate an approximate value for the emissivity from the data with a simple linear analysis.
Now, here’s the curious part. When I did that, I got an emissivity of 0.590 … which from everything I’ve read is too low.
So I thought, well, that kinda makes sense, because the temperature up where the radiation is coming from is cooler. But how much cooler? That depends on what altitude the radiation is coming from. Now my bible in these matters is “The Climate Near The Ground”, by Rudolph Geiger, which anyone interested in climate science should read. Geiger gives the following table for downwelling radiation (called “counterradiation” in those days):
Table 5-1 Contribution of various atmospheric layers to counterradiation received at the surface Layer thickness (m) % share of counterradiation 87 72.0 89 6.4 93 4.0 99 3.7 102 2.3 108 1.2
I figured that I could use that to give me at least a first cut at the temperature of the overlying atmosphere at altitude, using the lapse rate of one degree C per each hundred metres of altitude. For the six layers given by Geiger, this gives mid-layer temperature drops of 0.4°, 1.3°, 2.2°, 3.2°, 4.2°, and 5.2° degrees C. A weighted mean of these (allowing for the fourth power relationship) gives an average temperature drop of 0.85°C. This makes sense, because about three-quarters of the downwelling radiation comes from the bottom hundred metres of atmosphere, which is not much cooler than the surface.
However, this doesn’t solve the conundrum. Remember that I got an emissivity of 0.590 using the surface temperature. IF in fact on average the radiation is coming from a temperature which is 0.85°C cooler, then using that temperature it only brings the emissivity up to 0.595 … hmmm.
So that’s my puzzle for today. Is Geiger wrong about the source of the downwelling radiation? Is the emissivity of the atmosphere really on the order of 0.6? Is something else going on?
Inquiring minds wonder …
My best to everyone,
w.
AS USUAL: if you disagree with someone, please quote the exact words you disagree with. This lets all of us understand the exact nature of your objections.
CODE AND DATA: The R code, the functions, and the hundreds of daily files for 2010 are in a zipped folder called “SURFRAD Analysis”. WARNING: 21 megabyte file.
{UPDATE] Prompted by a typically detailed and interesting comment below from Dr. Robert Brown (rgbatduke), here is a scatterplot of the complete temperature and downwelling IR datasets:
[UPDATE 2] The same graph, but for Boulder, Colorado.
SURFRAD VARIABLES:
# station_name character station name, e. g., Goodwin Creek
# latitude real latitude in decimal degrees (e. g., 40.80)
# longitude real longitude in decimal degrees (e. g., 105.12)
# elevation integer elevation above sea level in meters
# year integer year, i.e., 1995
# jday integer Julian day (1 through 365 [or 366])
# month integer number of the month (1-12)
# day integer day of the month(1-31)
# hour integer hour of the day (0-23)
# min integer minute of the hour (0-59)
# dt real decimal time (hour.decimalminutes, e.g., 23.5 = 2330)
# zen real solar zenith angle (degrees)
# dw_solar real downwelling global solar (Watts m^-2)
# uw_solar real upwelling global solar (Watts m^-2)
# direct_n real direct-normal solar (Watts m^-2)
# diffuse real downwelling diffuse solar (Watts m^-2)
# dw_ir real downwelling thermal infrared (Watts m^-2)
# dw_casetemp real downwelling IR case temp. (K)
# dw_dometemp real downwelling IR dome temp. (K)
# uw_ir real upwelling thermal infrared (Watts m^-2)
# uw_casetemp real upwelling IR case temp. (K)
# uw_dometemp real upwelling IR dome temp. (K)
# uvb real global UVB (milliWatts m^-2)
# par real photosynthetically active radiation (Watts m^-2)
# netsolar real net solar (dw_solar – uw_solar) (Watts m^-2)
# netir real net infrared (dw_ir – uw_ir) (Watts m^-2)
# totalnet real net radiation (netsolar+netir) (Watts m^-2)
# temp real 10-meter air temperature (?C)
# rh real relative humidity (%)
# windspd real wind speed (ms^-1)
# winddir real wind direction (degrees, clockwise from north)
# pressure real station pressure (mb)
The emissivity off the atmosphere have allways been 0,598-0.6, it never changes and thats why more co2 doesnt raise temperature.
Thanks, Willis.
Interesting. Needed to re-read it twice. These are a sample of two. Normally if I saw the picture on the net I’d imagine “ahh, clouds!”
The S-B formulae gives the temperature at which the radiation is generated. The radiation at max. from your graph (365W/m2) gives a temperature of +10C, some 12C lower than the surface (10m0 level). With a standard lapse rate this is over 1000m above station level.
The actual fornulae ha another term on the right, e, but not knowing the material emitting the IR this term is unknown. Without e a black body emission is calculated.
Q=sigma e T^4 T being the absolute temperature. sigma 5.67^-8
Downwelling solar also needs to be in this picture. Then upwelling solar and upwelling IR and then net radiation in and net radiation out versus air temperature
I spent some time looking at the SurfRad station at Table Mountain Colorado. There are a number of radiation flows one needs to look at. And there is a really important piece missing from the measurements – how much net energy (joules) is the ground below the instruments absorbing/releasing as a 24 hour day goes by.
Generally, the surface air temperature is changing by extremely miniscule amounts per second (I mean like 0.002 joules/second) while very high radiation levels are flowing in and flowing out every second. The ground surface could be the shock absorber keeping the air temperature so steady while 800.000 joules/second is coming in from the Sun in mid-afternoon. Either that or the energy is flowing out as fast as it is coming in. Note one can see the influence of clouds (during the day and during the night).
Note that Upwelling IR is always “higher” than Downwelling IR which means this is really misdirection by the warmers. Downwelling IR should not heat up the air because more is actually Upwelling every second than is Downwelling. It should be thought of as a parcel of air where energy is constantly going up and down and all around as would be expected given this is a gas and there are photons constantly travelling through all gases all the time 24/7. Generally, IR energy is always moving up and out of this air parcel all the time. Sun comes up, solar radiation comes in and energy levels increase and the energy flows back up the air cloumn back to space as IR (every second 24/7).
http://s18.postimg.org/s66p367ft/Table_Mountain_All.png
Bill, Willis,
I live at 41N, just south of Lake Erie. I routinely measure sky temps 80-100F colder that ground temps, -40 to -60F or colder. Humidity reduces the difference between the surface and sky temps (as do clouds). So Willis I think the Mississippi Down welling IR is a large part from water vapor, While you see Bill’s Colorado station is much lower, which I believe is due to differences in water vapor between the two locations.
Bill, I think if you could get an IR read of the ground, you’d see air temps track the ground, with all the caveats. Like grass because it traps air, acts as an insulator, and on cold clear night is 10F colder than the ground and has frost, while the ground is still over 32F. Air temps over 20F grass is colder than air over 32F concrete. But I’ve also noticed 5F to 10F / hour cooling rates after sunset, drops to under a couple degrees/hour once rel humidity gets up over 80-85% as the air cools (which this wringing the water out of the air is where the moisture for dew and frost comes from).
This is why a change in Co2 has so little effect. When you clear the water out, it has 2-4F difference in clear sky temps, they coldest they get. Clouds are 40F to +70F warmer than clear skies. Water vapor adds from a few degrees to 80-90F to the clear sky temp. Because the difference in Miss and Colorado DW IR isn’t from Co2, it’s remained the same.
Mi Cro November 25, 2014 at 8:05 am Edit
Thanks, Mi, but presumably that’s using an IR thermometer which ASSUMES an emissivity … whereas I’m trying to calculate the emissivity from a known (or at least estimated) temperature.
w.
I understand. I had the same question (what e should I use, since I can change it). I found a study that said ~.7 (.72? so you’re not so far off). It was cold that night, so I had been measuring sub -60F temps, dropped the e down to .7 and it read somewhere closer to -100F.
I decided I could be more conservative, leave e at .95, it might very well be reading quite warm, but I figured it was still cold enough to show how little Co2 could possibly be contributing even being overly generous.
Isn’t the really important question the radiation over the ocean in the tropics, and how this varies with cloud. I’d like to sea something like this with also a measure of cloud directly overhead.
The really good part for all of us is that we can put all that evil “back radiation” to work as there is well over 200 watts/m² available 24/7 coming in from our atmosphere. All we need to do is tweak the doping for solar cell absorption to cover these wavelengths and we never have to worry about power again.</sarc>
That’s an understatement. Poked around on NOAA’s SURFRAD as well and the sensor they’re using for IR is so broadband it goes all the way out to 50µm… a considerable way into FIR. It also uses Parson’s black which NOAA has had problems with in the past see Section 3 of this NOAA Tech Memo here.
Bill Illis,
If the rate of outgoing radiation is decreased but incoming remains constant, what happens to temperature?
Brandon Gates:
In the middle of the Sahara, where the GHE is the least, due to the dryness, air temperature is the highest. In the humid tropics, where the the GHE is greatest, air temp maximum is 20°F to 30°F lower than the Sahara.
Try and explain that one in terms of your “down welling” IR.
Day time highs are predominately due to Solar, and the amount of moisture available at the ground. In this case with little moisture the Sahara warms quickly to a higher temp.
Now night time cooling is the domain where DWIR helps maintain temps, but again you see that in the case of your two locations, Co2 doesn’t add much to the IR from all of that water vapor in the tropics, and when you take the water vapor away in the Sahara, there’s so little energy from Co2, temps drop like a rock.
Micro:
The principle that I was trying to illustrate is this: the regions of stronger GHE have lower maximum temps.
This was in response to Brandon’s comment wherein he implicated higher air temps to DWIR. My observation compares low GHE (Sahara) to high GHE (tropics). The lower GHE (Sahara)
with the least DWIR (theoretically), has the highest temp. Brandon’s reasoning is the sort of screwy thinking that permeates climate science.
The next time I go sun-bathing, it can have a new name – “out to catch some downwelling solar”.
Doesn’t sound quite so lazy.
Out of my comfort zone here but I wonder how accurate you expect the surface temperatures to be when contrasted with the lapse rate of one degree C per each hundred metres of altitude?
I’m guessing the accuracy at the surface is finer than the approximation with altitude.
Thanks, M. Normally I would have only reported the emissivity to one decimal … but if I did that, the difference in emissivities from the two different temperatures wouldn’t be visible, as they only differ in the third decimal point. I wanted to point out how little difference the adjustment in temperature made to the emissivity.
w.
Thanks for the response.
That makes sense – I’m sorry I missed what you were saying with that accuracy.
Told you I was out of my comfort zone.
Willis, the Stefan-Boltzmann formula applies to a blackbody, or to a grey body if emissivity is taken into account. But in either case, the emissivity must be the same for all wavelengths. This is not true of the atmosphere. The atmosphere only radiates because of the presence of radiatively active gases. These do not cover the full spectrum and so the downward longwave radiation does not match a plank distribution. The atmosphere does not behave as a blackbody.
http://scienceofdoom.files.wordpress.com/2010/04/longwave-downward-radiation-surface-evans.png
There are large gaps in the spectrum, especially in the ‘atmospheric window’ between 8 and 12 microns. The Stefan-Boltzmann formula is not valid in this context.
.
Tsk, I should have got that.
You are right, MikeB.
“The atmosphere only radiates because of the presence of radiatively active gases”
Not true as stated. Somewhere north of one half is from liquid water droplets in clouds (60% coverage) whose radiation is much closer to full spectrum, but likewise not strickly a graybody or blackbody so the Stefan-Boltzmann formula is not valid in this context either. Though radiatively active, I just wouldn’t call these droplets a gas so your statement is misleading and lacking.
Well Wayne, , you are right that water droplets in clouds will radiate but these are not normally considered to be part of the atmosphere. I don’t really want to diverge into semantics here, but atmosphere is defined as a layer of GASES surrounding a planet. In normal usage It does not include liquid water because liquid water is, ipso facto, not a gas.
Saved me a reply. The S-B formula is sort of valid, you just have to integrate. That’s what Willis was trying to do by considering height, but technically you have to integrate height against transparency and temperature, as the mean free path of IR photons varies with frequency. On the other side of things (escaping photons) you have the same problem, only even more complex as pressure broadening means that heat “leaks out along the edges” of the lines as they sharpen at lower pressures at higher heights, narrowing the absorption bands above the emission bands below.
And don’t forget clouds. Some fraction of your downwelling energy is specular reflection from clouds, and hence is blackbody radiation from the ground in the holes where the atmosphere is transparent enough to permit wavelengths to reach the clouds to be reflected and come back.
The concept of “emissivity” under these circumstances isn’t to be taken too seriously as you are looking at something that is far from being a black body — wrong spectrum, partially transparent, partially reflective (in a time varying way) and sampling from a frequency-dependent range of temperatures, not a single temperature. This is why the problem is so complex. The errors in our ability to quantitatively evaluate what is going on are larger than the the effects we are trying to predict or understand, so that any small thing that we leave out of the dynamics might suffice to make our tentative beliefs incorrect.
Consider. You have a lovely graph for a single station. How universal is the result you plot? If the station were right next to a lake, would it be the same? How about a station in the heart of downtown or the middle of a shopping mall? How does a forest station compare to one in the middle of a plowed field. How does the plowed field fare in the winter time fallow or with a cover crop, vs freshly plowed in the spring, vs covered with barley or brocolli in midsummer? How does all of that compare to a station in mid-Sahara, in the Siberian marshes, on the Tibet plateau, in central Africa, in the middle of Antarctica? Does the curve for the station change from year to year, is it fundamentally different in fall/winter/spring/summer increments, and above all, what is the standard error? What is the variance in the sample data? The curves you have are remarkably smooth, but the underlying data could not possibly be that smooth and should show considerable seasonal variation.
rgb
I’ve been measuring zenith temps with an 8u-14u IR thermometer, since the 15u-16u Co2 bands are invisible, I’ve started adding 3-4W/m^2 back into what the thermometer is reading.
I do presume that to the thermometer 8u-14u does look like a “blackbody”, and at worst it’s measuring water vapor and then whatever temp the gases are at.
At 41N, when it’s cool with low humidity, Tzenith is easily 80F colder than my concrete sidewalk, and many times it’s over 100F colder. Clouds are always warmer than anything else, low puffy clouds are only 10-20F colder than the surface, high thin clouds might be 10-20F warmer than Tzenith, but they are always far warmer than humidity, which is far warmer than dry air.
So I’ve come to see the entire surface radiating huge amounts of energy to a very cold sky 24x7x365, with a blazing torch shining part of the time. And as soon as the torch moves on the surface starts to cool, but at almost no time during the nightly cooling process is the ultimate limit from Co2, it’s from water vapor.
@ RGB
I rarely disagree with anything you say, but I take issue with “Some fraction of your downwelling energy is specular reflection from clouds, and hence is blackbody radiation from the ground in the holes where the atmosphere is transparent enough to permit wavelengths to reach the clouds to be reflected and come back.”
Water droplets that make up the clouds are pretty close to blackbody absorbers/emitters. As such, they would absorb nearly all the IR coming up from the ground (not reflect it). They would emit *their* *own* blackbody thermal IR. So the spectrum should be at the temperature of the *clouds* not the temperature of the ground.
PS Here is a link to a site that uses MODTRAN (http://forecast.uchicago.edu/modtran.html) to give the calculated spectrum at various conditions. It is well worth exploring/bookmarking for anyone who wants to understand atmospheric IR. For example, it pretty well recreates the spectrum posted by MikeB if you look upward from the surface with mid-latitude winter conditions.
Sorry Tim, I stand corrected. I was thinking of the visible spectrum and their high albedo. I misplaced my copy of Petty’s book this summer and that’s my usual bible for checking things before I post them, as I mistrust both my own memory and my understanding.
rgb
“””””…..And don’t forget clouds. Some fraction of your downwelling energy is specular reflection from clouds, and hence is blackbody radiation from the ground in the holes where the atmosphere is transparent enough to permit wavelengths to reach the clouds to be reflected and come back……”””””
I don’t think clouds specularly reflect LWIR. Since clouds are water in liquid or solid form, they are strongly absorbing of LWIR radiation. Then they isotropically re-emit BB like radiation depending on the water temperature.
At solar wavelengths, water is transparent, but once again they only weakly reflect (about 2-3% reflectance). Mostly the droplets strongly refract the solar spectrum wavelengths, and convert the near collimated solar beam into a strongly focused beam, which then strongly diverges. Just a few drops in sequence and you get a complete wide angle scattering of the solar spectrum, which is not really specular reflection. The normal reflection coefficient for water (N = 1.333) is 2%
As for BB emission from the “atmosphere”, I thought gases could not absorb and emit thermal radiation spectra. Excuse me; that’s I thought people claim that gases don’t emit in the infrared (non GHGs)
CO_2 acts as a coupling between the atmospheric thermal reservoir and local radiation. In local thermal equilibrium (to the extent that the concept is valid in an open system conveying energy) the GHG molecules collide with the N_2 and O_2 molecules rapidly enough (as I noted) that they remain in equilibrium. The CO_2 is also coupled to the local radiation field (coarse grained over a much larger volume — mean free path order of a meter to meters). Following Kirchoff, it both absorbs radiation (instantly thermalized with the rest of the local atmosphere) and emits it (generally as energy picked up in collisions with the local atmosphere). As always, the directions of the average energy flow in the interactions is to try to establish detailed balance where local equilibrium is satisfied — the atmosphere warms if the local radiation field is warmer, cools if it is cooler, the atmosphere warms the local radiation field if it is cooler and cools it if it is warmer. This is on top of the adiabatic lapse rate, hence there is active transport of heat via radiation from lower horizontal slices to higher adjacent horizontal slices up to heights where the mean free path of in-band photons reaches “infinity” in the upward direction (becomes larger than the optical thickness of the remaining atmosphere).
Because of pressure broadening, each layer is slightly “leaky” — it emits from a slightly wider spectrum than the layer above it absorbs, so that radiation from the edges of the bands has a differential mean free path. This means that it doesn’t take all of the radiation in the surface bands the same amount of time to reach escape height, and that height itself varies with frequency. It is doubly complicated because there are multiple greenhouse gases with different absorption/emission bands. Still, the emitted in-band radiation follows a general intensity profile where the emission peaks roughly correspond to the local temperature of the emission height, see the many figures in Petty’s book or reproduced on WUWT by the article here:
http://wattsupwiththat.com/2011/03/10/visualizing-the-greenhouse-effect-emission-spectra/
which has my vote as one of the best all-time posts on WUWT. Note well that top of atmosphere spectrographs looking down and bottom of the atmosphere looking up are complements of one another, and that there is a clear relationship between the “blackbody temperature” of the emission height in-band for the primary gas(es) concerned and the spectral intensity.
To a physicist, these spectra are direct evidence of the greenhouse effect. That doesn’t make the differential radiation trapping easy to compute in a nonlinear chaotic double Navier-Stokes system evaluated on a rotating, tipped, oblate spheroid 70% covered with water and with a highly differential land surface height and character in an eccentric orbit around a rather variable star, but it leaves little doubt as to the probable average effect of increasing its atmospheric concentration.
rgb
Mi Cro — I think you are missing a lot more than 3 or 4 W/m^2. Measuring zenith at 38N here, I routinely see about -45C with an IR thermometer which is specified to cover 8-14um. However, if I make the same measurement using an IR thermometer that covers 5-20um then I get something around -21C. I have not worked out how much power is in the band from 14 to 20um but just from a visual estimate it appears to be quite a lot.
Mistake in that last post – I am seeing 7F on the 5-20um IR thermometer, and incorrectly converted that to -21C…it should be -14C.
I wonder if Miriam understood any of that?
MikeB
I think your Figure 1 is for dry air. H2O vapour is missing and would overwhelm the CO2 peak. As it says, “several greenhouse gases,” but not the most important one.
what MikeB said. The atmosphere is partly transparent in the IR, which causes the effect you are seeing.
Not to impose upon Dr. Spencer, but, although I knew vaguely that was the answer, I was hoping someone could give a black-body-for-dummies explanation of how solid-body interactions tend to smear the spectra out.
I believe many of us laymen continue to visit this site in the hope of finding such nuggets from time to time, and just sift through all the stories ridiculing the warmist dreck that issues with depressing reliability from the press and academe.
What Roy Spencer said about what MikeB said.
Willis, measuring the sky with an IR meter is more like measuring the temperature of a black-painted perforated metal sheet than a gray body. The gray body is an analogy giving an ‘average’ emissivity of what is really a ‘holey plate’. A highly emissive molecule of H2O is effectively ‘black’. But they are speckled/distributed through the air. The emissivity you calculated of about 0.6 is equivalent to saying you have a solid surface with an emissivity of 0.95 but at a lower temperature. The calculations show the total ‘back radiation’ but it is not from a homogeneous surface.
Regarding the water droplets, air has a lot of water droplets in it – they can be seen easily by illuminating them with a powerful handheld green laser pointer. Try it at night in cooling air. Water droplets are powerful emitters of IR and also reflect low incident angle radiation. The emissivity of water is approximately the same as black oil.
There is little point in discussing back radiation without also discussing the water vapour level. We can assume CO2 is evenly distributed by altitude but that is certainly not the case for water vapour. When water vapour is only 5 g per standard cubic metre, it is going to emit 10 times the IR of CO2 at 400 ppm.
Willis you say the air temperature cools quicker than the ground, but isn’t the air warmed by the ground not by the sun in which case the air should cool with the ground?
Regards kelvin
I’ll second that query
Note that the air temp correspond only to “downwelling” IR, as given in the scale of the graph, when in fact it is a flux of no particular direction. In this the jerks at NOAA bias their product.
In fact, it would be expected that air temp should correspond closely to the IR flux. No surprises here.
Also to ground temp., the ground being the source of the IR.
Yes and no. Because the atmosphere almost instantly thermalizes absorbed IR radiation, transferring the energy to the molecular KE of the surrounding air in a tiny fraction of the radiative lifetime, yes, the ground and air often/usually track one another pretty closely — there is rapid transfer when they aren’t in equilibrium.
However, it’s a dynamical system, with extremely variable heat capacity in the different parts. Cold air/warm air moving from one place to another can easily disequilibrate any given location. Given that 70% of the surface is water with a mix of latent heat and huge heat capacity and surface turbulence…
What would be really, really interesting would be to cover even one small selected patch of reality with a dense set of stations like this. For example, take Durham county (where I live in NC). Roll accept/reject random numbers to select (say) 10,000 sites all over the county (including in the middle of lakes or rivers or on the tops/sides of hills if that’s where the random gods will). Distribute specially designed stations with IR eyes that point up and down in addition to the usual thermometers, wind/rainfall-snowfall/pressure/humidity sensors on those points within (say) 10 meters (even when they aren’t conveniently located or might sample e.g. parking lots or asphalt rooftops). Monitor for a decade. In fact, since we’re going to the trouble, let’s go ahead and add a hundred blimps, similarly randomly located in 3d (including random heights, sampling full spectra facing both up and down, local temperature, wind, and so on). Or do full soundings at those sites 12x a day.
We might actually learn enough to have an idea of what “average temperature” could sensibly mean. We might learn about heat transport. We might be able to inform models, instead of just guessing and filling in whatever we think might be true.
rgb
Dr, Brown:
Excellent suggestion. For a fraction of the money squandered on miserably failed, GIGO models, real climate science could be advanced by acquiring more and better relevant data. We need more observation and fewer models, ie none at all yet, in the primitive state of our understanding.
rgbatduke
November 25, 2014 at 9:40 am
” …. What would be really, really interesting would be to cover even one small selected patch of reality with a dense set of stations like this…. (including random heights, sampling full spectra facing both up and down, local temperature, wind, and so on)…..”
===========
That would settle a lot of assumptions now being made with regards to models.
In consideration of Willis’ review suggesting that the lower region of the atmosphere may be responsible for ~ 70% of DWIR, a relatively inexpensive gathering of data from a couple of points (geographically) utilizing perhaps 4 or 5 small planes crossing over a given point at various elevations within a short period of time measuring all the parameters you stated (i.e. IR up, IR down, temp, RH/dew point, etc) could yield a valuable trove of information.
This could possibly be done using a string of balloons if the FAA would permit.
I would be surprised if this hasn’t been done.
eyesonu:
Such measurements have been made already at a number of instrumented towers scattered around the world. Miskolczy has published analysis results for, IIRC, the tower maintained by KNMI in the Netherlands. Naturally, because they lead to conclusions contrary to academic dogma, his work has been excoriated by the high priests of AGW.
Willis says: “Other than the atmosphere starting to cool a bit earlier in the day than the ground (as we’d expect from the relative masses) they match up perfectly.”
I’m not a meteorologist and i have never lived in that area, but another explanation would be fewer clouds during the afternoon. As others have pointed out, much of hte back-radiation comes from clouds, so clear skies would radiate less at the same temperature.
Perhaps the data also includes cloud cover, and you could see if is it less cloudy when the IR curve drops below the temperature curve.
Reblogged this on Centinel2012 and commented:
Good work — I was not aware of these stations!
Air temperature is not only due to radiative heating, but also conduction directly from the surface to the air, as any amateur astronomer knows. Turbulence over buildings destroys the quality of images, and they are to be avoided. It’s not like the building is venting hot air, it’s the roof and windows heating the surrounding air by contact and causing the heated air to rise. Similarly, any pilot knows heated air rises from the ground, and if it contains sufficient moisture, a cloud may form, and a big enough cloud may begin to rain. So if you want to find updrafts, go from cloud to cloud (VFR, staying underneath).
I assume the instrument measures infrared along its entire frequency? But to properly understand the post and to educate myself I must ask. What are the outer bounds of the instrument in measuring incoming IR?
I have answered my own question. From the http://www.esrl.noaa.gov/gmd/grad/surfrad/surfpage2.html website:
“Radiation measurements at SURFRAD stations cover the range of the electro- magnetic spectrum that affects the earth/atmosphere system. Global solar and its components are measured separately. Total downwelling (global) solar radiation is measured on the main platform by an upward looking broadband pyranometer. The direct component is monitored with a normal incidence pyrheliometer (or NIP) mounted on an automatic sun tracker, and the diffuse component is measured by a shaded pyranometer that rides on the solar tracker. Diffuse solar was not in the original suite of SURFRAD measurements. The shaded pyranometer was added in 1996 when a support platform with a shade arm mechanism was fitted to the trackers. A third pyranometer is mounted facing downward on a crossarm near the top of the 10-meter tower to measure solar radiation reflected from the surface. An upward looking pyrgeometer on the main platform measures long wave (thermal infrared) radiation emitted downward by clouds and other atmospheric constituents. Another pyrgeometer, mounted facing downward on the crossarm atop the tower, senses upwelling long wave radiation. These measurements of upwelling and downwelling in the solar and infrared wavebands constitute the complete surface radiation budget.”
Odd that it matches linearly. Shouldn’t it require a log scale?
Ln(1+x) = x + …..
Looks linear enough to me.
of course that’s x _x^2 / 2 + x^3 / 3 _ etc
x – (x^2)/2 + (x^3)/3 –
I’m talking about that the scale on the left for temp (C) and the scale on the right for radiation (W/m^2) are both linear scales. Assuming that P = aT^4, isn’t anyone bothered by the linear scale on the axes? What am I missing?
Over the interval in question, there’s not much difference between the linear and the T^4 variability.
w.
I think I just said what it is you are missing. And if not, then Willis just said it here too.
But in case it is of interest to anyone, I recently did a calculation of a simple model, where the BB radiation of a static T = To body is compared to the same body at the same AVERAGE Temperature To, but actually having a cyclic Temperature (sinusoidal), where T = To.(1 + k.sin (2pi t/tau))
Integrating the total radiant energy emitted during a complete cycle of the Temperature cycle:
The static case gives E = sigma. To^4 tau j/m^2
The cyclic case gives E = sigma. To^4 tau. (1 + 3k^2 + k^4 / 8)
The k^4 / 8 term is rather negligible.
For k = 0.1, the AC case gives 3% higher total black body energy emission, so such a body would cool faster, and would have a lower (not much) average Temperature, than if the Temperature was absolutely constant.
This is what Dr Svalgaard disputed, and is the reason, I don’t accept 342 W/m^2 as the TSI for planet earth. It really is 1360 whatever.
But the difference is small enough that linear scales suffice as Willis used.
(21+273)^4 / (12+273)^4 * 330 = 373.7
Graph shows about 360 @ 21 C. Seems like a significant difference to me.
Willis
Sorry for not quoting your exact words, but I have a general enquiry.
You often comment along the lines of how much warmer it is when it is a cloudy night because clouds reradiate downwards more LWIR. How does that proposition fit in with your observation that “three-quarters of the downwelling radiation comes from the bottom hundred metres of atmosphere…”.
If three quarters of all DWLWIR comes from the bottom 100 metres of the atmosphere (which I do not challenge), then how do high level clouds at say 2,000 to 6,000 metres make a substantial difference, save other than reduce heat loss by restricting convection.
Or because as the atmosphere cools water vapor changes state to liquid on cloud condensation nuclei and radiate the latent heat of state change. There is no need for ‘reradiation’ at all the heat was up there all the time.
Ian W,
I have given much thought along the lines of your comment for quite some time.
One other thought that keeps nagging me is also the increased specific heat contained in the air that contains a likelihood of more water vapor in cloudy conditions as opposed to dry clear conditions.
I don’t have the ability to properly explain/express that as well as others here.
==========
@ Bill Illis (November 25, 2014 at 5:58 am)
Your graphic is very interesting.
===========
Anyway, this thread is going to provide some very interesting comments and discussion.
richard verney November 25, 2014 at 6:04 am
richard, I have always assumed that it is because the downwelling IR from the clouds is absorbed and re-radiated from the lower levels … but I’m up for all suggestions.
w.
It seems to more closely track the surface, but I’ll have to scan across a cloud bottom with the Sun behind it to see if it changes or not.
Just above Dr. Brown said that IR absorbed in the atmosphere thermalizes. Absorbed and re-radiated almost never happens in the lower atmosphere, only much higher and closer to, if not at, the Top of Atmosphere. Downwelling is indeed a misnomer, as the entire atmosphere radiates in all directions at all times.
Dr. Brown also said that clouds “spectrally,” which means like a mirror (I had to look it up) reflect IR from the Ground in the Holes where the ground can radiate directly to space, these holes being in the IR spectrum from 8 to 12 microns. It is all so simple now…
The condensation of the water vapour at, say, 2000m forms clouds and releases a great deal of heat: latent heat of condensation. That heat thermalizes the surrounding….water vapour! The air has so much water vapour that is why it is condensing in the first place. It is saturated. Clouds are surrounded by water vapour, not dry air.
That water vapour, now warmed by the latent heat released by the condensing water vapour, radiates in the IR band, cooling as it does so. The cloud water droplets are themselves IR-radiative with an emissivity of about 0.98. Their behaviour in the IR band is completely different from their behaviour in the visible range. All that IR radiation goes up (to be intercepted by the clouds and sent down again) or directly down to the ground. Obviously there is leakage at the ‘edges’. The net effect is for clouds to form an insulating blanket much more real than the misnamed ‘greenhouse effect’ claimed for CO2. These water and water vapour effects overwhelm any small variations in CO2 concentration of a few hundred ppm.
“””…Dr. Brown also said that clouds “spectrally,” which means like a mirror (I had to look it up)…”””
No he did not.
He said “specularly”, which is not “spectrally”.
“richard, I have always assumed that it is because the downwelling IR from the clouds is absorbed and re-radiated from the lower levels … but I’m up for all suggestions.”
====================================================
This brings up many questions. The lower atmospheric levels GHG molecules are emitting not just LWIR from the ground I think, but conducted and convected energy as well, from the thermal dynamic equilibrium of exchanged energy through conduction, with collisional exchange of energy far more common throughout the lower troposphere, correct?
If this is correct, then is not much ? some? of the 50% of the energy sent to space from emitting GHGs, from non- GHG molecules, which if they had transferred their energy to other non-GHG molecules instead of GHG molecules, would still be in the atmosphere, thus the affect of the GHG molecule was to radiate away conducted energy, thus cooling through shortening the residence time of energy from non-GHG molecules.
????
I think I am looking for a ratio regarding how much of the energy GHG molecules radiate to space is from conducted energy, vs LWIR from the ground?
Let me further clarify my question. I think I am looking for a ratio regarding how much of the energy GHG molecules radiate to space is from conducted energy – convected energy – evaporative condensed energy vs LWIR from the ground?
(It appear logical to me that if said energy from the first three sources conducts to a GHG molecule, it has a 50 percent chance of accelerating the loss of said energy to space vs. that same energy conducting to a non GHG molecule where the chance of it escaping to space would be 0.)
I suggest you calculate dew point from relative humidity, pressure, and atmospheric temperature. Then apply the S-B calculation. I suspect the measured radiation is from the condensation/evaporation process with possibly a relatively small amount from CO2 at the same temperature. NOAA/ESRL records average hourly met and CO2 data from Pt Barrow, Mauna Loa, Samoa, and South Pole http://ds.data.jma.go.jp/gmd/wdcgg/cgi-bin/wdcgg/map_search.cgi. The annual files are in text format for easy copy and paste. These files do not contain radiation data.
I have noticed that once teh Sun sets, it cools very quickly, until rel Humidity climbs as air temps drop, this quick rate under clear skies if the limit due to water and Co2, once RelH gets to 80-85% the cooling rate drops to a fairly low rate, which continues until the Sunrises.
I think this is more important than many other factors. It is water that keeps the heat from radiating to space. When water is turn into ice the planet cools. When all the ice melts the planet warms. As has been often noted the planet appears to have a maximum temperature. That is probably because the atmosphere holds only so much water and that is that.
I think the important point is this.
From the surface (which while they keep trying to move the goal post, is what’s critical), for the ~50% of the planet under clouds, a change in Co2 has 0 influence on surface temps. For the remaining ~50% of the planet, the fast cooling rate (up to 10F/hour or more) right after the Sunset, is impacted far more by the day’s % humidity than Co2 (multiple 10’s to 100+ w/m^2 vs 4w/m^2), then once the surface water vapor starts condensing out this sets the cooling rate (to a degree/hour or less).
But the slow cooling limit is controlled by surface temps, so an increase in Co2 would at worst delay the transition from fast cooling to slow cooling for minutes.
Also, while there’s not a lot of slope on Willis’s temp graph, you can see the rate change during the early morning.
If this SURFRAD database is indeed so cumbersome, how can anyone make use of it efficiently? Quite possibly, deviant Gruberians eschew objective, rational, analysis/interpretation… so, much like AW’s original reconciliation of disparate Surface Station readings, mayhap some competent researcher of integrity could undertake to render this extraordinary 15-year resource intelligible.
Lloyd,
The files are plain ASCII text files, fixed width format, one for each day of observation for each station. IOW, quite similar to daily weather station data from NCDC. A one-line wget command downloads all the files for one station, it took an hour. While that was running, I have a boilerplate script which uses some pre-written helper functions that I configured to import the data into a database. By the time the download was finished I was ready to start the import which took another hour. So in the space of two hours I was up and running writing queries to analyze and plot ~20 years worth of data which contain up to one-minute resolution in later years (three minutes for the early years).
Fascinating stuff, really and well worth the minor effort. h/t to Willis for turning me on to it.
[Thank you for making that effort. .mod]
I have also looked at surfrad and got some information overload. I really mis the possibility to plot temperature and radiation at the same time. I wonder if it was overcast days or clear sky.
I sometimes measure the sky temperature with an infrared termometer, and clear sky is below -20C, overcast between 10 and -5C. Gives an estimate of the cloud hight.
Willis
Compliments on delving into Surfad. Your graph shows a remarkably close relationship. The difference in early afternoon may be cloud cover per your thermostat hypothesis. (Interesting comments by Bill Illis above).
Re your query on atmospheric emissivity (from the peanut gallery) I expect the quantitative value is calculable by using a quantitative Line By Line emissivity model calculated across all emitting wavelengths summed over numerous elevations and adjusted for cloud cover. Complement that with a thermodynamic model of the lapse rate pressure, temperature and atmospheric composition, or empirical model – adjusted for local humidity. See:
R. Saunders, P. Rayer, P. Brunel, A. von Engeln, N. Bormann, L. Strow, S. Hannon, S. Heilliette, Xu Liu, F. Miskolczi, Y. Han, G. Masiello, J.-L. Moncet, Gennady Uymin, V. Sherlock, and D. S. Turner A comparison of radiative transfer models for simulating Atmospheric Infrared Sounder (AIRS) radiances, Journal of Geophysical Research: Atmospheres (1984–2012) Volume 112, Issue D1, 16 January 2007
e.g., Ferenc Miskolczi’s High-resolution Atmospheric Radiative Transfer Code (HARTCODE), (Miskolczi et al., 1990) and 1D climate models, and Robert H. Essenhigh’s atmospheric lapse model.
F. Miskolczi Modeling downward Surface Longwave Flux Density for Global Change Applications and Comparison with Pyregeometer Measurements J. Atmospheric Oceanic Technology, 1994 V. 11 p 608
Note Miskolczi’s development of Tau E, the Radiative Equilibrium Flux Optical Thickness, and E sub D super A = the All Sky Long Wave Downward flux to the ground (p 32) in:
Ferenc Mark Miskolczi, The Greenhouse Effect and the Infrared Radiative Structure of the Earth’s Atmosphere, F Development in Earth Science Volume 2, 2014 http://atlatszo.hu/wp-content/uploads/2011/07/article.pdf
Note differences in clear vs cloud methodology.
On thermodynamic lapse rate, see Robert H. Essenhigh, Prediction of the Standard Atmosphere Profiles of Temperature, Pressure, and Density with Height for the Lower Atmosphere by Solution of the (S−S) Integral Equations of Transfer and Evaluation of the Potential for Profile Perturbation by Combustion Emissions, Energy Fuels, 2006, 20 (3), 1057-1067 • DOI: 10.1021/ef050276y
(Contact for Robert Essenhigh at Ohio State)
Developing a quantitative local model for downwelling radiation and surface temperature along these lines from half of Surfad would be a good quantitative modeling development with the potential for quantitative validation by the other half of Surfad.
Eratta: SURFRAD
David,
Thank you for the links above. I found the one by Ferenc Mark Miskolczi, The Greenhouse Effect and the Infrared Radiative Structure of the Earth’s Atmosphere, very interesting. I will read again when time allows.
The one linking to Robert H. Essenhigh was pay walled so only the abstract was viewed.
Essenhigh’s model was extended in the public document:
Sreekanth Kolan, Study of Energy Balance between Lower and Upper Atmosphere MSc Thesis, Ohio State 2009. See Ch. 5-7.
Thanks
So that’s my puzzle for today. Is Geiger wrong about the source of the downwelling radiation? Is the emissivity of the atmosphere really on the order of 0.6? Is something else going on?
=============
the contradiction suggest there is an error in the assumptions. the contribution of convection/conduction?
Plotting the first derivative of the curves might be informative, to see if cause and effect can be isolated.
http://web.iitd.ac.in/~prabal/gas-radiation.pdf
Link is to a short paper that has the Hottel charts in it. It can be seen that the maximum emissivity for CO2 is .2 as shown in on the charts for the temperature shown on the graph above. For the 362 W/m^2 shown on the graph presented to come from CO2 the temperature of the gas would have to be 422.7 K.
Thank you to Willis and all commenters for an interesting thread.
Water vapour v.s. water droplets: an experiment you can do at home.
Pull out your IR thermometer and set the emissivity to 0.95 or 0.98. Cheapies are fixed at 0.95.
Boil your kettle and point the IR meter sensor at the clear steam as it emerges from the kettle mouth. Get close.
Next point it at the white condensed water vapour located a centimeter further from the mouth.
Are they the same temperature?
What is the radiation source for the IR in the white condensed cloud?
Dr. Robert, as always your clear and lucid comments are much appreciated. You say:
rgbatduke November 25, 2014 at 5:39 am Edit
True dat … particularly the part about the errors.
Your usual good questions. As I said, this is a first look. Here’s a second look at the same data, but this time as a scatterplot of the entire dataset. I invite interpretations of what the different parts of the graph reveal …
The light black lines seem to run in the same sense as the S-B lines … but then there’s the black section above the line at high temperatures, and a host of other details.
In any case, my thanks to you and to all the commenters.
w.
My “seat of the pants” interpretation …
* The bottom-most data points (lowest emissivity around 0.7) correspond to clear, low-humidity days. Lack of clouds and lack of water vapor limits the back-radiation.
* The top of hte bottom band (emissivity around 0.85) corresponds to clear, high-humidity days. The extra water vapor provides a bit more back-radiation
* the upper band (highest emissivty) represents cloudy days, with lots of back-radiation from the nearly-blackbody clouds.
If I am right, then I predict that temperatures above ~ 30 C almost always have clouds, and the coldest temperatures are nearly always clear. I’ve never been to Mississippi, but I suspect these are both reasonable predictions for this area.
Two additional bits ….
1. The ranges of power agree quite well with the predictions of MODTRAN for low humidity at the low power end of things to cloud cover at the high power end of things.
2. The strokes running parallel to the colored lines would be the warming and cooling during the day with approximately constant humidity; the vertical strokes would be the rapid changes from clear to cloudy (or vice versa) at relatively constant temperature.
I am probably asking the impossible here but is there any way to put a time series here to the black lines either by color or some other mechanism. Maybe color coded by month/quarter or the holy grail by surface temps or some form of representation of both?
You are on to something big here on this thread!
Willis,
I’d love to see what the Colorado site looks like as you’ve plotted Miss. My thought is that you’ve mostly just plotted the response of water vapor, similar to the graphs you’ve done with SST’s limiting to 30C or so.
I would expect Colorado to get close to 150W/m^2 by 0C. The black shifted down to the left based on the difference in humidity between the two locations.
The black blob is the effect of low level clouds, they are the closest anything is to ground temps.
Lewindowsky and any other psuedo-sociologist will likely say that this demonstrates a deep-seated need on your part to take the:
http://theinkblot.com/
test.
A similar experiment in Germany seems to have gotten similar emissivities if I’ve understood their table correctly.
http://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0CDQQFjAD&url=http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F222679178_Downward_atmospheric_longwave_irradiance_under_clear_and_cloudy_skies_Measurement_and_parameterization%2Flinks%2F0912f5072b20c07b49000000&ei=7-p0VJOeCfSCsQS-pIDwDg&usg=AFQjCNGh3ofYnYDUPudTWiJr39qenKzEkw&bvm=bv.80185997,d.cWc
If You use Your emissivity of 0,59 in the formula here:
http://en.wikipedia.org/wiki/Effective_temperature
You get the result that the average temperature of the Earth is 288K or 15°C.
And by that have you reduced the greenhouse effect, as it is usually explained, to null.
Coldlynx,
Actually, the fact that emissivity is not close to 1.0 is *confirmation* of the greenhouse effect. Without an atmosphere that limits outgoing radiation, we would see the (nearly) blackbody radiation from the oceans and lands, and a 288 K surface would rapidly cool. The effective emissivity of ~ 0.6 can only be due to the GHGs (along with aerosols and clouds) that reduce the outgoing radiation so that the surface can warm to 288 K.
What you say applies at night but I’m not so sure that it applies during the day.
Without GHGs day time temperatures would reach maximum within a couple of hours very similar to the moon.
But the Earth warms much slower, it gets nowhere near the moons max temperature even though it warms for on average 6 hours
This slow warming is undoubtedly cooling. The question is which effect is bigger, night time warming or day time cooling.
If warming was bigger, each morning would be a little warmer than before, leading to the maxium quicker than the day before. That’s just not happening and nor is the reverse.
Therefore the effect of a GH atmosphere is to distribute heat, not increase or decrease it. IMHO
Does not the lowered Temperature of the earth simply reflect the fact (pun intended) that the earth has an albedo of 0.35 or 0.39 or whatever, so it does not absorb TSI x pi x R^2 solar energy.
Seems to me that emissivity and albedo are getting confused here.
george e. smith
November 26, 2014 at 12:09 pm
No. I think rather that the “published and accepted” value of earth’s “average albedo” is very carefully set to match (and back-calculate) Trenberth’s “Published and Accepted” flat-plate earth radiation model that is used to demonstrate the flat plate average earth temperature calculations ….
See the circularity there?
Unfortunately the design of the instrumentation reads more than just incoming IR. It also ‘reads’ the kinetic energy of the gas in the enclosure. If you are impressed by the label ‘Scientific Equipment’ without understanding what is truly measured then good luck to you in your delusion.
My goodness, Alex … are you always this unpleasant?
In any case, some evidence to back up your claim would be useful …
I ask for evidence because I did read the ReadMe file, and it says:
Doesn’t sound to me like it is “reading” the kinetic energy of the gas in the enclosure … if you have evidence to the contrary now would be the time to bring it up.
w.
Sorry Willis. I’m not having a go at you. I think you do a marvellous job of analysing data. I had a quick read of the Surfrad website and checked the instrumentation used. My comment was based on that, not on your work. Thermopiles are just thermometers and would read the air temperature as well as the incident IR. Which is why I was not surprised that your graph with the blue line and black line tracked each other so closely. However, I will take your advice and read in more detail about the instrumentation used. I may retract my earlier comment or I will find some links to back up my words.
Thanks, Alex, I’ll be interested in your findings.
w.
Hi Willis.
This is what I found.
http://www.eppleylab.com/instrumentation/precision_infrared_radiometer.htm
Very light on detail and has the same mistake as on the Surfrad website ie using the word ‘silicone’ instead ‘silicon’. What a wild goose chase that was.
Wikipedia had a description and diagrams of the equipment
http://en.wikipedia.org/wiki/Pyrgeometer
There is a little nonsense in the equations. Mainly the implication that downwelling IR heats the sensor and makes it hot which then emits IR and that somehow balances things. I could say the same thing about a thermometer I left in the sun.
The main thing I was looking for was confirmed in the diagram. There is a pocket of air in the measuring chamber which would clearly have to be at the temperature of the surroundings. So that air temperature would be read by the thermopile sensor. The only way to subtract the influence of the air in the chamber is to remove the air completely and make it a vacuum chamber.
My other concern is with the optical filter. Optical filters in IR work are a real nuisance.
There is no broad spectrum optical filter. These filters only work in narrow-ish bands.
http://www.pmoptics.com/silicon.html
that is far different to the band claimed to be measured in the wikipedia article on pyrgeometers.
http://www.bing.com/images/search?q=wg295+glass&qpvt=WG295+glass&FORM=IGRE This is just an example of some filters.
Optical filters also get hot and emit radiation but probably not as blackbodies or graybodies but as ‘non-gray’ bodies which have emission curves in different wavelengths and don’t look remotely like blackbody curves. So in actuality I don’t really know what that instrument is reading. Although I know if I took that instrument into a darkened room it would only read the ambient air temperature-and that is so wrong.
I also feel that the term PIR is misapplied to this type of instrumentation. It is, admittedly, a passive device like a liquid in glass thermometer and not a platinum resistance thermometer or a thermistor that require an active circuit to function.
In my world this is a PIR
http://en.wikipedia.org/wiki/Passive_infrared_sensor
and not this
http://en.wikipedia.org/wiki/Thermopile
I hope I haven’t rambled on too long
Well as far as I am aware, these broad band radiation sensitive detectors (thermal) ONLY read correctly when they are in “thermal equilibrium”.
That means the entire cavity (and its contents) have reached thermal equilibrium with the incoming radiation, so the radiation emitted from the cavity aperture, exactly matches the incoming radiation both in amount and spectral composition.
This is one of the few o.ccasions wherein Kirchoff’s theorem is applicable, and emission equals absorption.
So Alex, I believe your gizmo is not reading the correct Temperature UNTIL it and the air it contains have reached an isothermal equilibrium state with the incoming radiation.
If it is not in such a condition, the cavity and thermopile sensor are still increasing in Temperature, along with the contained air.
So I think Willis is in good standing on this.
That is just my personal opinion, and should be viewed in light of an expert’s opinion, that I should forever more refrain from even attempting to discuss physics in learned company (such as that expert).
With a emissivity of 0.59 is the “greenhouse effect” 100% explained by the atmosphere emissivity by GHG. Not by radiation from higher and by that colder altitudes, as the greenhouse effect is usually explained,
The classical claim of radiative transfer of heat in the atmosphere to colder altitudes is not in the above linked formula still is Willis emissivty value spot on to calculate the real temperature for our Earth.
I know very well that GHG cause the emissivity in the atmosphere but in the common simplified explanation of greenhouse effect is often using a much higher emissivity value, close to 1, and then explain the 33K greenhouse effect with radiative transfer models in the atmosphere.
Willis emissivity value in the formula reduced the radiative transfer explanation to null since all of grenhouse effect of 33 K is included in a lower and acutually measured real emissivity value.
I qoute Wilis:
“I don’t know why, but I wasn’t exactly expecting that … which is the best part of science.”
PS
Note what happend with temperature with changed emissivity values in the formula.
Higher emissivity value reduce temperature. Just saying….
DS
Are these data from a IRTS-P sensor used by NOOA weather stations? They explain:” The IRTS-P sensor is mounted vertically downward near the end of one of the 3-meter cross-member arms, 1.3 meters above the ground surface. The sensor is inserted into a Holleander tubing cross fitting perpendicular to the 3-meter cross-member and pointed downward….
This temperature is measured to determine the effective “skin temperature” of the “field of view” ground surface. Ground Surface (Skin) Temperature, along with wind speed and solar radiation provide information to allow for correction of observed air temperature data due to solar heating.”
“Now my bible in these matters is “The Climate Near The Ground”, by Rudolph Geiger, which anyone interested in climate science should read.”
A copy of which has been scanned and made freely available in a number of formats by Archive.org here: https://archive.org/details/climatenearthegr032657mbp with the PDF version here: https://ia700504.us.archive.org/4/items/climatenearthegr032657mbp/climatenearthegr032657mbp.pdf.
I will be ordering the referenced book “The Climate Near The Ground”, by Rudolph Geiger. Amazon ics currently out of stock on the hard back 6th edition
A paper back is fine with me. Have the later editions been corrupted? There may be “used” copies available and at this point I’m motivated. I downloaded a pdf and scanned through it but the old time way of white pages works best for me.
Any feed back will be appreciated.
O/T I was looking for the above book and during a ‘google’ search came across this :
http://wattsupwiththat.com/2012/06/18/time-lags-in-the-climate-system/
It was a while back
Hi Willis,
I suspect a plot of upwelling IR minus downwelling IR versus temperature would be informative, in that it would show how net radiative heat loss from the surface changes with surface temperature.
Further SURFRAD results … the same as above, but for Boulder Colorado 2010.
As is often the case it seems the limit at the hot end is much clearer than the limit at the bottom end. Interesting differences from the Mississippi data.
w.
A thermostat maybe?
neither colored curve fit (red nor blue) actually follows the data trend very well. Sure, there is lots of scatter, but the grouping, the general trend of the data is not tracking with that those two approximations (particularly at the lower (less than 5 deg C) levels.).
mpainter,
As Mi Cro has pointed out, both you and Bill Illis need to take downwelling solar radiation into account. Neither water vapor nor CO2 nor any other “greenhouse” gas are heat sources in the sense that they are not adding any additional energy to the system. Only the Sun does that in a significantly life-giving way, and good thing for us that it does. GHGs effectively act as insulators — they reduce the rate at which the planet is able to dissipate absorbed solar energy back into space. Again, good thing for us that they do or it would be quite cold on this rock.
One need look no further to understand this than our natural satellite the Moon; lacking an appreciable atmosphere but having the same solar constant its average surface temperature is somewhere on the order of -5°C even though its albedo of ~0.12 is less than half that of the Earth’s which presently averages ~0.28. There are other differences and complexities, but the significantly cooler average surface temperature is easily explained by the Moon’s lack of an insulating atmospheric blanket. No argument from this “warmist” that GHGs are essential for life as we have evolved to know it.
Now that I’ve reintroduced the overlooked downwelling radiation from the largest fusion reactor in the local neighborhood, I can address your main question which is a good one. Speaking first in net global terms, the bulk of solar energy dispersion at the surface is accomplished via water evaporation and vertical mass transfer due to thermal convection. Obviously a dry desert doesn’t contain much surface moisture, so thermals are pretty much it.
How significant is that you ask. Well, you’d be hating life on a hot day if you didn’t have sweat glands in your skin, but let’s put some numbers to this. To Trenberth’s (in)famous graphic we go: http://www.cgd.ucar.edu/cas/Topics/Fig1_GheatMap.png
Slightly out of date (IIRC the net downward flux imbalance is presently estimated at ~0.4 W/m^2 with a healthy error margin) but it works for this purpose: evapotransportation accounts for 80 W/m^2, thermals 17. These are net global figures, mind, so applying them naively to local conditions isn’t the most robust scientific practice but we might be able to derive a decent 0th approximation from them. Let me see if I can.
Tallying up the all net fluxes at the surface I come up with 18 W/m^2. Multiply by the canonical value of 0.8°C/W*m^2 and we get 14.2°C for the average global surface temperature. [1] If I back out the entire 80 W/m^2 evapotranspiration component to represent a perfectly (unrealistic) dry desert net flux at the surface jumps to 98 W/m^2, multiplied by 0.8°C/W*m^2 gets a whopping 78.4°C which cannot remotely be correct, so what gives?
Well, just as the Saharan surface is dry, so is the atmosphere above it. From the diagram the net greenhouse effect is 157 W/m^2 [2]. From memory I know that about 60% of the net global effect is due to water vapor and clouds which don’t happen too often in the Sahara.
However, absent water vapor the part of CO2’s absorption spectrum that normally overlaps with water picks up some of the slack. So let’s call the net greenhouse effect in the desert 50% of the global average or 78.5 W/m^2. Subtract that from our previously calculated 98 W/m^2 and we get 19.5 W/m^2. Multiply that by 0.8°C/W*m^2 and the result is 15.6°C. Add back to that the world average of 14.4°C and we get an average of 30°C for the Sahara.
Google the phrase: “average temperature of the sahara desert” and an info box pops up which says: The Sahara desert generally features an arid climate. The Sahara desert is one of the hottest regions of the world, with a mean temperature over 30 °C (86 °F). Variations may also be huge, from over 50 °C (120 °F) during the day during the summer, to temperatures below 0 at night in summer.
I did not look it up beforehand though I will admit I had a fair idea it would be in that neighborhood. I left lots of stuff out and greatly oversimplified a few things [3], so some of this is pure dumb luck on my part [4]. But as a “blind” estimate I’m still rather pleased with the result.
——————–
[1] Which is the published value circa 2009, so yes this chart is definitely out of date — more recently published figures put average temps at ~16°C … lookit that, in 3 years we wily alarmists have conjured 1.8°C of warming out of thin air!
[2] The math here is 356 W/m^2 upwelling IR from the surface absorbed in the troposphere, less 169 + 30 emitted into space at TOA giving 157 W/m^2.
[3] One missing thing to think about is that thermals are quite a bit stronger in the desert, especially hot ones, so 17 W/m^2 heat loss from the surface is likely quite a bit low. What goes up must come back down, and it does so a bit cooler than when since at higher altitudes there’s a clearer free path for GHGs to emit into space. On the other hand as Mi Cro has correctly pointed out, at night dry/cloudless air allows for greater radiative heat loss than a humid/cloudy one which would also tend to bring down the average temperature. On the gripping hand, it rains a lot in the jungle, which means cloud cover that blocks incoming sunlight during the daytime, plus brings cooled water down to the surface. This stuff really is NOT simple.
Brandon Gates, this thread was shaping up to be one of the most interesting ones I’ve read on this site and then you come along and make it twice as interesting in a few compelling, easy to understand paragraphs (I’m a geologist and mining/processing engineer – not a physicist). You mention you are a ‘warmist’, but I don’t detect you to consider us on our way to the alarmist’s perilous future from Anthropogenic GHG increases.
The hottest temp RECORDED supposedly is the Death Valley one of about 57C so I’m sure we have exceeded 65C frequently. Given ”trade wind” type air flow over the Sahara and other winds (Sirocco northwards over the Mediterranean and the harmattan that blows southward toward the equatorial region) this air replacement could account for the dozen degrees moderation of your calculated 78C.
Gary,
Thank you for the kind compliment. I too am enjoying this very interesting thread. Unfortunately the math in the comment you’re responding to is badly off. I should have known better than to be able to get to a ballpark approximation doing arithmetic using the global energy budget and relying on memory for the little bit I’ve read about deserts. I’m now in the midst of a crash course and will publish a correction sometime tonight or tomorrow.
I did understand that max temperatures get into the 50s and 60s but I was intentionally going after the annual mean.
Gary, PS:
Mostly correct. By default I reject politics of fear no matter who engages in them. That doesn’t mean I’m not concerned about potential risks, however I recognize that the current state of the science has far more uncertainties looking forward than back. In short, my view comes from a risk management perspective — when uncertain err on the side of caution. As a practical matter, ruining the economy by doubling energy prices would be immediately catastrophic. From a political perspective, selling risky and potentially expensive economic solutions is a dog that won’t hunt. Where I look for balance and compromise, others are engaged in a winner-take-all mentality. I think we do know how to mitigate and reduce risk (reduce emissions) but the best near term solutions (nuclear, geothermal) don’t happen and decent compromises which have evolved because of a favorable market (shale gas replacing coal) are vehemently opposed. Makes me a tad cranky at times.
Brandon you said…
I disagree with the above WADR
There is no point talking about ‘average’ temperatures. Both the Moon and Earth have a day cycle. We know that during the day, both warming and cooling takes place, and during the night cooling only takes place.
In order to understand the (so called) GHE, we’d first need to understand what happens during the day and what happens during the night.
Taking your example of the Moon, the dramatic drop in temperatures as soon as the sun sets is never experienced near the surface on Earth. The closest we get is at desert locations where the GHE is the weakest. We experience the exact opposite at tropical wet regions where the cooling is slowed.
This is a WARMING EFFECT.
On the other hand, the exact opposite hapens during daylight hours. On the Moon, temperatures rise well above the highest on Earth within a couple of hours [so the argument that the Lunar surface gets warmer because of the length of day (14 earth days) doesn’t wash.]
Likewise, dry desert regions reach a higher temperature than wet tropical regions EVEN THOUGH THE DESERT STARTS THE DAY AT A LOWER TEMPERATURE. So the GHE reduces the rate of warming during the day.
This is a COOLING EFFECT [Note: If a reduction in the rate of cooling can be expressed as a warming effect (as many have argued), then a reduction in the rate of warming may be expressed as a cooling effect]
So then, in order to be able to claim the GHE warms or cools this planet, one would need to determine which effect is greater. The answer is obvious, occams razor.
Mi Cro,
Nowhere are these factors better known than amongst the researchers responsible for your understanding of them. I know where your knowledge comes from because I’ve read a bunch of their papers, x2 explanations from secondary sources to help translate unfamiliar terminology into lay language I can better comprehend.
Now, the planet is composed of dry cold, dry hot, wet cold and wet hot regions, both land and ocean. Latitude affects the incident angle of incoming solar energy. Albedos differ by locale and/or season. It’s cloudy in some places year round, clear in other places year round, mixed depending on season in others. Big cities absorb more solar energy during the day than rural areas. As big cities get bigger, they incrementally do more of that over time.
As the growing UHI effect is something that is generally understood conceptually here — and oft discussed — it stymies me that so many here can’t apply a similar line of thinking to the incremental increase of well-mixed GHGs over the course of increased industrialization. To wit: gradual long-term changes can have a cumulative effect on the mean over extended periods of time even though their contributions are a fractional percentage of the instantaneous net.
Logically then, if The Pause “falsifies” CO2’s role, it also nukes the much emphasized UHI effect too. Amirite? Maybe, maybe not. That’s where making observations and doing a heck of a lot of math to quantify things becomes essential.
When the scope of study is global, one hopes all that math arrives at an approximate global estimate of the NET effects of ALL the reasonably known and understood individual component dynamics. Of COURSE the Sahara is going to work differently than the Amazon. Anyone having more than average familiarity with climate science knows that the Arctic and Antarctic behave differently despite their facile similarities — as in both are at much higher latitudes and friggin cold and dry compared to northern Brazil.
To your credit you remembered that downwelling solar flux needs to be accounted for before I got around to reminding Bill and mpainter. I don’t know about you, but the two of them are still stuck on the notion that if upwelling IR is always greater than downwelling IR from the atmosphere then the lot of us on the consensus side of the fence must be bonkers. Well that’s silly, not just because they left the dang Sun out of their “gotcha” rebuttal, they obviously haven’t stopped to consider the implications of net flux on the RATE of energy transfer.
So back to my question for Bill Illis and now you and mpainter: if the RATE of outgoing flux is reduced but incoming flux remains constant, what happens to temperature?
C’ Mon, Brandon, pay attention. I have answered your question. The atm with the higher greenhouse gas concentration has the lowest air temp., under constant insolation. Earth says so. Your model says otherwise.
What will you do Brandon? Will you claim water vapor is a positive feedback to increased atm. CO2? That is what your experts claim. I repeat: higher greenhouse gas concentrations —-> lower max air temp.
mpainter,
Oh but I am.
‘Fraid not old bean. I asked an easy 1st year physics theoretical question and you’ve responded with anecdotal evidence that is factually correct and that’s about it. I may as well tell you that as the number of pirates decreases temperature goes up. It’s an awfully pretty correlation, no?
Also higher min air temp in the Amazon. In the Sahara, the min nightly temp routinely goes below freezing in SUMMER. Both places work out to an average annual temperature of …. drumroll please …. ~30°C, though the Amazon runs cooler at ~27°C. Think daytime cloud cover, and rainfall (any time of day) for starters.
Now for the third time, tell me what reducing the rate of outgoing flux does to temperature when incoming flux is constant?
Okay Brandon,
You say “reducing the rate of outgoing flux”, so what reduces the rate of outgoing flux in your book? I assume that you mean by this the effect of increased concentration of greenhouse cases, and by this the rate of outgoing flux (IR) is reduced (more correctly, however, retarded). This is the assumption upon which I based my reply. Now, pay close attention. Go to the Sahara. There, the daytime highs exceed 125°F in summer. The concentration of ghg there is very low, compared to the tropics. You wish to see what happens when you increase greenhouse gas (which by your AGW theory increases DWIR). Go to the tropics, where the atm. concentration of GHG is much higher. Does max air temp. increase?
No. So why did not the increase of DWIR raise max air temp.? Please answer, as I have tried to answer you.
Brandon, you might not be able to overcome your indoctrination of AGW theory. That’s okay, I understand. But that does not mean that I lack intelligence. You cannot explain, by your theory, why max temps are higher where the GHE is lower, and vice versa. You speak in terms of DWIR. Well, my friend, your theory has been thrown into the ditch by this curve in the road.
Now, once again:
Higher ghg (tropics)–>lower max temp;
Lower ghg (Sahara)–> higher max.
Explain again what all of that DWIR is supposed to do, please and thank you.
And Brandon,
The example is not “anecdotal” as you said, but empirical. I recognize that some theorists are not capable of addressing the issue empirically. I suspect that this may be the case here.
Also Brandon, you grant that my example as “factually correct but that’s about it”.
My method is to obtain the facts and proceed from there.
What is your method, pray tell.
Brandon Gates
November 26, 2014 at 2:48 pm and 4:24 pm
=============
I’m not sure what to make of your two previous comments. I will read yet again carefully.
eyesonu,
Well the one to mpainter has a pretty stupid math error in it. I got very lucky to get the correct answer.
A correct answer? I would need to read it all again to look for one.
eyesonu,
30°C average temperature for the Sahara was my calculated answer, and that’s the published value. The stupid error is the final step, “Multiply that by 0.8°C/W*m^2 and the result is 15.6°C. Add back to that the world average of 14.4°C and we get an average of 30°C for the Sahara.” Adding back the world average is double counting and I can’t do that. My reasoning about the lack of evaporative cooling from the surface jibes with published literature but pretty much the rest of my math falls apart. I’m wrong, and I wish I could take that post back but I can’t.
Brandon Gates
Try instead a day-to-day radiation budget: You have the right idea, but are trying to get “flat plate worldwide averages” from a single location at a single latitude with a single combination of air temperature (day and night, humidity, atmosphere clarity, solar radiation, and thermal mass.
Just do a day-and-night cycle at one point.
Get that right.
Then extrapolate over a full season at that latitude. With that latitude’s weather conditions (humidity, clarity, pressure, clouds, etc.)
You’ve got the right idea: And starting with the Sahara (dry, little or no evaporation, no phase changes, no ice or water conflict, steady winds, low latitude so radiation is predictable over the whole year) are almost as “easy” as getting the moon right. 8<)
RACookPE1978,
Good suggestions, thanks. My first inclination is to pick a grid and mine KNMI for data, though I might be limited to monthly resolution. I’ll try that first, but I think looking at things like temperature and humidity at up to hourly resolution might tell me something that even daily min/max/means wouldn’t. Ideas?
No.
Be humble. And get the radiation and IR (inbound) and LW (outbound) and thermal mass correct for the simplest problem first.
The moon. At its equator. 8<)
Then … When you are satisfied with your results against experimental results, work on the Sahara.
Brandon
That’s why I bought a cheap weather station, I wanted to “see” how weather evolved.
What I’ve found really interesting is that while absolute humidity changes slowly, rel humidity (which drives a lot of surface processes), swings wildly with temp changes.
I’m not sure if I uploaded it to SourceForge or not, but I have daily data on 1×1 degree cells if you want it.
Brandon Gates,
Why don’t you put your current “project” on hold and follow what Willis has presented and use your energy to help sort out that which Willis has so gratefully brought forth. This may be a holy grail in understanding climate related topics. Follow the lead or take it within the context of this thread. This thread may lead to the biggest breakthrough in a long time. Don’t let a golden opportunity pass. Focus! If you know the answer let us know. If you don’t then start looking.
Brandon Gates
November 26, 2014 at 11:20 am
================
In your comment earlier in this thread you stated that you had downloaded the data that Willis is looking at. Why don’t you plot several days at each station in a similar manner as Bill Illis (November 25, 2014 at 5:58 am) did in one of his earlier comments. Do include temps also. No averaging, just raw data. Place those results on a site and provide link here so we can all see.
eyesonu, I’m working on them.
Willis: The GHG’s in the atmospheric don’t absorb or emit in the “window” (8-14 um). The main source of radiation at some of these wavelengths is space (which is filled with blackbody radiation appropriate for 3 degK).
Emissivity is a problematic concept to apply to any anything that is partially transparent and/or lacks homogeneous temperature. The atmosphere has both complications. By definition, emissivity is the ratio of emitted radiation to the radiation emitted by a blackbody of the “same” temperature. At the infrared wavelengths where the atmosphere is totally or partially transparent, the radiation comes from above the atmosphere – where it is 3 degK.
When you tell me that the calculated emissivity is 0.59, I feel like asking 59% of what? Our partially atmosphere as a blackbody or greybody. The appropriate question to ask is does the DLR we observed match the predictions of radiative transfer theory.
mpainter,
1) GHGs and clouds reduce outgoing flux.
2) The Sahara gets relatively hot during the day mainly because a) there is little cooling effect from water evaporating at the surface, b) there are few clouds to block incoming sunlight, c) its low latitude gives sunlight a high angle of incidence and d) it doesn’t rain very often. These daytime factors in sum offset the decreased DWIR due to atmospheric moisture in wetter climates at similar latitudes.
3) At night in the Sahara the dearth of atmospheric moisture and cloud cover means less DWIR, so it cools far more rapidly and get far colder than rain forests at similar latitudes.
4) My use of “anecdotal” in this context means non-representative. As in a) too small a sample and b) not considering other relevant and available observations. Yes, your two data points (max daytime temp, minimal atmospheric moisture content) are factual observations so formally they are empirical evidence. However they are too narrowly applied.
5) My method is to obtain as many relevant facts as are available and/or that I can reasonably comprehend.
Again, your question is a good, properly skeptical, one. Your adamant refusal to consider other observations and pointers toward other physical processes is not good.
Brandon
You claim that clouds warm by “reducing outgoing flux” and that they cool by ” blocking incoming sunlight”.
You need to resolve that. Do clouds cool in the day or warm ( please recall the issue is max temp.)? My belief is clouds cool in daytime, not warm.
Otherwise I agree that humidity makes the difference, that is, water and water vapor. Note that the GHE is due to water, mainly, and humidity ( water and vapor) determines t-max, hence the higher the humidity, the greater GHE, the lower t-max.
That bears repeating:
higher humidity—>greater GHE—>
Lower t-max.
In short, the strength of the GHE, locally, depends on local humidity, as rgb was at pains to point out up thread.
In conclusion, the role of water is misapprehended by AGW theory because water acts as a coolant in all its phases in daytime (which reminds me: you omitted the convective factor in your above response).
mpainter,
I am aware of that. Max temps usually occur during the daytime suggesting that the dominant radiative effect is the Sun. Since one half of the planet is is in darkness at any given moment, it seems folly to ignore that part of the equation.
Yes, we agree. Clouds not only block sunlight from reaching the surface, they have high albedos which reflect incoming solar radiation back into space. During the daytime, clouds will tend to lower max temps. At night, clouds do the opposite and tend to raise min temps. Both are radiative effects.
I mentioned convection in the form of thermals several posts ago. I’ve explained the physics of non-radiative water effects several times now. Your turn to explain instead of just repeating the same assertions over and over.
Brandon,
We seem to agree substantially. Here we part company, I imagine.
The GHE in fact moderates air temp. of the earth during solar forcing. That AGW crowd would have us believe otherwise but our empirical observations are conclusive, as in the tmax of the Sahara vs. the tropics.
Atm. water vapor derives from surface cooling and the vapor phase is a stage of the cooling process that involves both surface and atm. The next step is convection of latent heat aloft where it is released far above the earth’s surface. The radiative flux is the dominant process under scant GHE, but it is subsumed in the cooling effect of water, water vapor, and the phase changes, this being the climate process of the tropics.
HENCE, the stronger the GHE, the lesser the role of IR flux in determining air tmax.
Night, under no solar forcing, is subject to different considerations.
mpainter commented on
IMO the issue is that while both water vapor and Co2 are GHG’s, water also has other roles in the climate that Co2 does not. They are not equal!
Surface temps cover all three states of water, Co2 is only a gases. Clouds while comprised by water, they do not acts the same as a GHG, We don’t see clouds of Co2.
On an snowball earth, I think Co2 acts to kick start global warming, until the water cycle starts again.
RACookPE1978,
Since SURFRAD is the main topic of this thread, ATM I’m working on those data for Colorado, Las Vegas, Missouri and West Virgina. If I have time before comments close I’ll take another swipe at the Moon vs. the Sahara vs. the Amazon.
(Very minor) errata: Illinois, not West Virginia.
RACookPE1978,
I loaded a bunch of files for Missouri, Nevada and Colorado up to a publicly shared Google Drive folder: https://drive.google.com/drive/#folders/0B1C2T0pQeiaSM2JmNks4cFgyQmM
mpainter,
I think you meant to write that water vapor derives from surface heating. At least I hope you did.
I mostly agree. Technically latent heat is energy released or absorbed by a phase change.
That statement is quite odd since by definition GHGs are molecules with strong vibrational modes in the IR spectrum.
Yes, the system behaves differently when not being pumped by solar energy. Sort of like your freezer behaves differently when you unplug it from the wall outlet. But I promise you that none of the underlying physics change when it gets dark or pull the plug on your fridge.
Brandon,
Still stuck in the IR rut?
Then are you content to repeat the mistakes of your teachers?
The GHE moderates temperature because it is essentially water. AGW theory incorrectly has it raising temp., but observations tell us otherwise. So go plug the fridge back in, relax, have a beer, and reflect on the wonderful benefits of atm. CO2.
wxobserver commented
First, I presume you’re used both at the same time, to make sure they measured they same Tzenith.
The 3-4 W/m^2 forcing is just the increase in human Co2. So, it doesn’t really surprise me, what this says is that the spectrum isn’t a black body, which if I thought about it, makes sense.
I would like to see what the spectrum looks like though (as opposed to the one shown in the thread rgb referenced).
Do you have any technical info on the 5-20u thermometer?