Guest Post by Willis Eschenbach
Despite doing lots of research and investigations over the last few weeks, I’ve written little. Well, actually, I’ve published little, although I’ve written a lot. But I didn’t publish what I’d done, there was no wonder in it, no awe. So I tossed it all out and started “simply messing about”, as the Toad had it. For no apparent reason, I got to looking at the various methods for estimating the downwelling longwave radiation (DLR) based on surface conditions. DLR is the radiation emitted by the atmosphere which is directed downwards towards the earth. There’s a good summary of the various DLR estimation methods here.
In any case, I wanted to compare the estimated DLR to the DLR from the CERES satellite observations. I used the “Brunt” method, which calculates an “effective emissivity” from the vapor pressure. The vapor pressure in turn is calculated from the surface temperature. I subtracted the satellite observations from the Brunt estimate. Figure 1 shows the result.
Figure 1. Difference between the downwelling longwave radiation (DLR) as calculated by Brunt, and the downwelling longwave radiation dataset from the CERES satellite data.
I busted out laughing when I saw that graphic come up on the silver screen. I do my science visually, by painting the transformations and relationships in color. And in general, I have only the vaguest idea of what any given graphic will look like before it is displayed. So watching the graphics appear onscreen is like opening a line of scientific presents. Each one is unexpected, each one reveals new things.
This one was funny to me because it was such an excellent and detailed map of the desert and arid areas of the planet. From the Sahara to the Atacama Desert, the Gobi, the American Southwest, the Arabian Peninsula, the Namib Desert, it’s all laid out in precise detail. Heck, you can even see the green areas of Australia as a thin strip along the east and north coasts.
This is a curious result because the CERES satellite doesn’t measure water vapor … but what we have in Figure 1 is a map of water vapor. Over the desert areas we get less downwelling radiation than the estimate suggests, because water vapor is the main greenhouse gas. In the desert the air is so dry that more radiation escapes to space, and less is absorbed and radiated downwards (and upwards) by the atmosphere. It also shows the moistest areas of the planet (dark green and blue). These are in the equatorial tropical forests, where transpiration combines with evaporation. This leads to lots of water vapor, and a concomitant increase in DLR above what the estimate suggests.
This is the first time I’ve looked at the difference between a variable in the CERES dataset and an estimate of that variable. They say that all models are wrong, but some are useful. This model of downwelling longwave radiation is obviously wrong … but it’s useful because of exactly where and how much it is wrong.
Which leads to the final surprise for me, which was the size of the deviations from the expected DLR. From very dry regions to very wet regions is a range on the order of 100 W/m2 of downwelling LW radiation … I didn’t think it would be that big.
Anyhow, that’s the kind of thing I like to write about—the unexpected. For me, the adventure of science is never knowing which bush might be the one that hides the rabbit …
Regards to everyone,
w.
As Always: If you disagree with someone, please quote their exact words so we can all understand your objection.
A note on the Brunt Method: The Brunt method estimates the “effective emission” as a function of the form
a1 + a2 * sqrt( vapor_pressure )
Per the above citation, the canonical values for a1 and a2 are 0.51 and 0.066.
When I fitted the values, I got a1 and a2 as 0.65 and 0.029. I thought this might be a result of including the ocean. So I looked at just land, which gave a1 and a2 as 0.65 and 0.024. And looking at just the ocean I got 0.66 and 0.030. None of these are near the values given in the reference. However, they work quite well, and the canonical figures give much larger errors. Go figure.
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Well worth waiting for-thanks!
Kind of obvious point but if water vapour is the largest “greenhouse gas” and desert areas, where there is the smallest atmospheric concentration of it, achieve the hottest day time surface temperatures of planet, doesn’t this say something important about the whole concept of “the greenhouse effect”?
No. Deserts are famous for getting very cold at night.
Wicked, these areas get this hot during the day because of their latitudes. Most of these deserts sit in areas that have a 1 – 2 punch, the atmosphere generally stays in a high pressure mode causing subsidence and a adibiatic warming. So not only is the air warming as it descends in these latitudes but there is a lack of cloud cover to block solar energy. I could further develop how most deserts form on the eastern sides of oceans but it leads to the same outcome, cold eastern ocean currents have less evaporation which leads to less cloud cover… a 1-2 punch. Then at night comes the ‘Greenhouse effect’, since there is very little water vapor, the most important greenhouse gas. There is very little trapping of the outgoing LW radiation and subsequently at night when solar energy no longer warms the surface there is a lot less down welling LW radiation. Which is the point of Willis’ s essay.
SOME deserts are famous for getting very cold at night. While its true that deserts heat and cool faster than moist areas that have cloud cover some remain quite warm at night. While I have shivered in below zero C temperatures in central Australia I have also sweated buckets trying to sleep in a motel in Beatty Nevada with air temperatures higher than 30 C at midnight.
Then there are the Antarctic deserts where the MAX summer temperatures get close to zero C but winter temperatures drop to -30 C and coupled with adiabatic winds that can hit 200 mph even a native of Wisconsin would admit to it being a mite chilly.
There isn’t a lot of downwelling LW during the day either.
Anyone near one of these places they can measure the IR temp of the clear sky? Where I’m at even during the day the sky is very cold when it’s clear and dry out.
moisture cools in the day and slows down cooling at night.
Brandon Gates
March 28, 2015 at 1:47 am
I think it depends on the desert.
It is currently 98°F in Palm Springs, CA, with a forecast high of 99° for today and 66° for tonight.
http://www.accuweather.com/en/us/palm-springs-ca/92262/weather-forecast/331971
Brian – your 1-2 punch is right on the money. The cloud cover, regardless of the absolute humidity, is going to be minimal when there is a preponderance of descending air.
Clouds mostly warm the surface at night and these are generally absent. The high daytime temperature invites some mechanism, ANY mechanism, to keep some heat in during the night. Nada. Just a smattering of CO2 and a dark night sky.
The temperature of the surface is far higher than the hot desert air. I wonder if this has been well considered. A cubic metre of air doesn’t hold much energy, let’s say in round numbers = 0.0012 MJ/K. The sand mass heated and cooled holds about 1 MJ/K per sq M of surface. The loss of heat into the sky from a sq km of desert surface is maybe 2×10^13 J per night. The Sahara loses about 10^20 J per night from the surface, by radiation I suppose.
Willis you are really onto something. I find the map astonishing. Completely unexpected. My knee-jerk response is that the loss of heat from the (very hot) surface has to be modelled in cells and the humidity of the air over each cell considered.
Atmospheric dust may be very important when making the calculation because a lot of the time the Sahel, for example, has a completely unseen sun on bright, cloudless days. One cannot even see where the sun is, the obscuration by dust is so complete.
Viva measurements! Viva!
Bit of a myth that hot deserts always get very cold at night.
Night time temperatures can be below freezing during “winter” when the daytime maximum might be around 25C .
However when the daytime maximum is 45C or higher the minimum might be 30C….generally not considered as very cold.
Thus is a good example
http://www.kilty.com/freeze.htm
Steve P,
Well sure. It’s almost always freaking cold in Antartica.
Mmmhmm. Of course one evening’s weather isn’t going to tell us much about climactic factors. Mean diurnal temperature range in Celsius by calendar month:
Month Palm Springs Sahara Amazon
1 15.16 16.31 9.39
2 15.77 17.20 9.32
3 16.60 17.28 8.98
4 17.93 17.08 9.99
5 18.57 17.05 11.01
6 19.57 16.59 12.60
7 16.57 15.42 13.90
8 15.98 14.26 14.42
9 17.12 15.25 12.87
10 17.44 15.99 12.13
11 16.22 16.31 10.47
12 15.06 15.74 9.75
ann mean 16.83 16.21 11.24
Using data from CRU TS3.22 Tmax-Tmin available on KNMI climate explorer. “Palm Springs” is the 5×5 grid containing the city. “Sahara” and “Amazon” are both 15×15 grids which I chose by eyeballing a map.
I’ve worked in the deserts of southern Algeria, Egypt and western Oman. By day, these places are the hottest on earth in summer with weeks on end having daily maxima in the mid 50 degC (in Oman). They do not get very cold at night after a hot day unless you consider 30 degC cold. That is a 25 degC swing. In about 6 years in these places I never experienced a cold night after a hot day unless a new weather system moved in. In winter the nights after mild days are cold and they feel a lot colder because the humidity is normally very low. Having also worked in central Australia for many years I can assure everyone that summer temps there are a few degrees less than the other deserts mentioned above and the following night temps are correspondingly a bit less. The biggest swing in temperatures I ever experienced were in central Siberia at Novosibirsk where after a low 30’s degree C day there were snow flurries at night – this area was not a desert.
4 eyes,
I don’t consider that cold. It’s not the comparative which illustrates the principle …
… that is the comparative which does. So again, the average annual climatological mean diurnal temperature ranges for Palm Springs, the Sahara and the Amazon are 16.83, 16.21 and 11.24 degrees Celsius respectively. In the Amazon, nightly temperatures are not as cool relative to its daytime high as the desert regions cited — to the tune of 5°C — because the Amazon has far more absolute humidity and cloud cover. Of those, clouds are the more noticeable radiative effect, something I learned about on cloudy winter nights in southern Ohio — they block a hell of a lot of outgoing IR and “bounce” it back toward the surface, resulting in a smaller net rate of heat loss at night.
It’s only a tendency though. There are other effects from how air masses move around which may or may not affect cloud cover any particular evening — think frontal systems, inversions, etc. — but which do have an effect on that night’s temperature. The radiative effects are most detectable and predictable in long-term means.
Amazon vs. Sahara are two good examples because they’re such distinctly different climates despite being at similar latitudes. The Sahara’s annual mean temp is about 30 °C. The Amazon, 27°C — even though it’s about 5 degrees closer to the equator. Two main reasons for that: clouds during the day in the Amazon reflecting incoming sunlight, and more surface evaporation. After the sun goes down is where the radiative effects of heat loss come into play. That shows up very clearly in the long term mean diurnal temperature swing.
Brandon, I dug through the weather data I have and tried to select the period with the largest min-max-min solar day swing in temps. I did try to exclude “weather” and did things like required high pressure, low wind speeds, and a wide range in temps, it pulled about 250 records out of 122 million, the swings were right around 30-40F maximum.
This link to Kevin Kilty’s blog has a report of someone dying of exposure on a reasonably warm day.
More water vapor in the Amazon atmosphere is conducting more heat away.
50 is not warm compared to 98.6. There is no mystery about dying of exposure in 50 degree weather. With no energy input, and enough time, a delta T of 48.6 will take it’s toll.
VikingExplorer,
Especially during the day. Isn’t that more or less what I wrote?
micro6500,
Yes, to really isolate the radiative effects, you have to control for all sorts of other factors. That’s one reason why Willis used a CERES clear-sky product — to control for the effect of cloudiness. And lack of clouds is one big reason why hot deserts tend to have large diurnal temp swings. I’d think that’s generally the biggest reason.
What data were you scanning? Is this Sahara only, or worldwide?
Same world wide ncdc gsod data.
One of the big reason I got my own weather station was to see if I could tell clear skies from data.
micro6500,
Gotcha.
Something I’ve found very useful for that exercise: http://wattsupwiththat.com/2014/11/25/a-first-look-at-surfrad/
My vote for best Willis Eschenbach post, and second-best WUWT post EVAR. First place is actually a tie:
http://wattsupwiththat.com/2013/05/27/new-wuwt-tv-segment-slaying-the-slayers-with-watts/
http://wattsupwiththat.com/2013/05/28/slaying-the-slayers-with-watts-part-2/
You lot don’t always make me want to tear my hair out, donchaknow ….
Brandon, Willis,
This quote:
Goes with what I’ve been saying about what my IR thermometer reads when pointed up.
But I think I’m changing my mind about the absurdity of DW LW IR being ~300W/m2, because within a few days, I can have clear sky days with a 20-30F difference in average air temps, and it’s not solar, as it’s only days apart. So it has to be from the air. And I can “see” humidity in 8-14u, so I would expect in the SURFRAD mississippi location the sky is probably 30F, as opposed to the -60 to -70 I can go out and measure here (if the sky was clear).
I always assumed I was measuring the average temp of molecules where the non-radiating gasses KE was shared with in this case water, and I was seeing the average KE of water in 8-14u the general temp of those gases. I also felt this was reasonable because you can use this same cold sky to freeze water when it’s above freezing.
But if the air mass itself that is 41F right now, that will warm some today, and cool some tonight, but will be only a little warmer tomorrow (dur to a longer day than today), how does that air mass cool if it’s invisible in the 8-14u IR band (and yes i know where this is leading, that’s why I’ve explained as much as I have here)?
I think someone calculated the thermal mass of the non-radiating atm as about the same as the surface mass that’s exchanging heat at about the same mass?
Makes me think, and that’s a dangerous thing to do.
4 eyes
“Weeks on end in the mid 50’s”
Sounds like wild exaggeration to me to put it politely. The hottest temperature officially recorded anywhere in Oman is 50.8 deg C Perhaps your thermometer was close to the outlet from your air conditioner. Most towns in Oman have a diurnal range of 10 to 12 degrees in summer – typically low 40’s to around 30. It may be a couple of degrees more in a rural location admittedly but hardly 25
You what? Think about what you have said. Pease
Deserts have large variations between daytime and nighttime temperatures because dry air has a low heat capacity compared to moist air.
Kind of obvious point but if water vapour is the largest “greenhouse gas” and desert areas, where there is the smallest atmospheric concentration of it, achieve the hottest day time surface temperatures of the planet, doesn’t this say something important about the whole concept of “the greenhouse effect”?
Thanks, Wicked. We’re looking at clear-sky conditions in the map above (no clouds). Desert areas get very hot during the day because they don’t have many clouds. The effect of this is much larger than any decreases in daytime downwelling longwave.
And they get very cold during the night because there’s little water vapor to absorb radiation and leave the earth warmer.
So no, they don’t say much about the greenhouse effect.
Regards,
w.
Funny, because it certainly looks like more conventional forms of heat transfer through different mediums, than conforming to “back radiation” or other “greenhouse” attributes. Different densities and mass affecting speed of absorbtion and conduction and the like. Deserts heat up faster and cool down faster. Mean temperature? Similar to non desert areas of similar latitude and altitude. So where is the “greenhouse” evidence?
POI, There are stories, anecdotal I accept, of British troops in the Sahara during WW2 suffering from frost bite during the cold nights! I am sure there may be some of American troops serving there too.
Wicked I tend to agree with you.
One obvious point is how much energy is there in the atmosphere. When it is dry, the atmosphere contains little energy, and hence such energy as there is is quickly lost. This is the dry desert night scenario.
On the other hand when the atmosphere is humid, the atmosphere contains a lot of energy and hence it takes time for the atmosphere to lose this energy, and hence night time temperatures fall away slowly. Thiis is the cloudy night scenario seen in most latitudes outside the tropics.
Thise that consider that how we experience daytime/nightime temperatures is a matter of radiative energy, and back radiation thereof, fail to look at the obvious, namle how much humidity and hence how much energy is entrapped in tyhe atmosphere itself.
Where I live (the shores of the Mediterranean) cloudy nights in summer are usually cool whereas clear sky nights in summer are usually warm. It would appear that is largely a matter of daytime humidity.
Thank you Richard.
When we actually consider the MASSIVE changes in humidity that occur in any location daily or the MASSIVE differences of humidity between locations with similar latitude and altitude and see the TINY differences in mean temperature that these changes make (especially if you compare temperatures of a specific day of the year at a specific atmospheric pressure as well), I’m amazed that the Greenhouse theory gets the traction it does.
That said, the principle of Occams Razor is the one scientists of any persuasion find hardest to apply. What use is your expensive degree (Preconceived Hypothesis Disorder) and how can you be paid as an “expert” if answers are simple and can be understood by anyone who managed to get into high school?
Never mind IR. I see “downwelling” visible light all day long: I see the sky.
The narrative has it that visible light comes from the Sun, some is absorbed and the rest reflected to space: if that were true, the sky would be dark.
wickedwenchfan
March 28, 2015 at 7:18 am
… , the principle of Occams Razor is the one scientists of any persuasion find hardest to apply. What use is your expensive degree (Preconceived Hypothesis Disorder) and how can you be paid as an “expert” if answers are simple and can be understood by anyone who managed to get into high school?
__
Maximum giggle induction points awarded.
@Sleepsalot
Yes. I worked on the desert for 20 years in Yuma until I retired 5 years ago. There were afternoons when the sky was so dark it looked like you photoshopped it in pictures. If fluffy white clouds were present the bottoms were saturated with the reflected desert light and the effect was even more unreal. One of those afternoons a test engineer pointed his pyrometer at the dark rocky ground and discovered it was 145 degrees F. No wonder my feet felt hot and wet with sweat.
In the last ten years the sky seems to have become a less saturated blue on any day here in Yuma. I’ve seen some explanations of what may be the cause, but I don’t have the science background to really evaluate them.
The only possible variable is water vapor, and the PDO started to change about then, changing the path of the jet stream, probably not a coincidence with your changing sky.
wickedwenchfan,
You’re right. It does say something about the ‘greenhouse effect’. The atmospheric ‘greenhouse effect‘ is after all supposed to make the surface below warmer (its temperature higher) ON AVERAGE. Clouds allegedly contribute significantly (~25%) to this atmospheric ‘greenhouse (average, net warming) effect’.
Problem is, the AVERAGE (annual) sfc temps in tropical/subtropical desert and generally dry areas are consistently higher, not lower, by several degrees (corrected for altitude) than the ones in tropical/subtropical rainforest and generally wet areas.
And this is in spite of the fact that the surface in those dry areas absorbs on average about the same amount of solar radiation that the surface in those wet areas does (‘All Sky’, according to CERES), while at the same time radiating back out a lot more – the mean ‘dry’ sfc temperature is higher than the ‘wet’, so mean blackbody emission (UWLWIR ‘flux’) is more intense (by perhaps 10-20 W/m2; ‘All Sky’, CERES), coupled with a much less intense atmospheric DWLWIR ‘flux’, making up a considerably larger sfc ‘net radiative (radiant heat) loss’ flux in the dry areas than in the wet (by about 45-50 W/m2).
Which means that, radiationwise, the sfc in the dry areas on average heats about the same (from direct solar input), but at the same time cools a lot more (from ‘net radiative (radiant heat) loss’) than the sfc in the wet areas. And is STILL substantially warmer, on average.
You could also look at it this way: The sfc in tropical/subtropical desert/dry areas absorbs a much smaller total mean radiative input (solar SW + atmospheric LW) (~550 W/m2) than what the sfc in tropical/subtropical rainforest/wet areas does (~580 W/m2). (That’s about 30 extra W/m2 of radiative input.) While at the same time radiating out (UWLWIR) about 10-20 W/m2 more on average.
So why aren’t the latter areas (the ‘wet’ ones) warmer on average? Why are the former areas (the ‘dry’ ones) warmer?
What is even more interesting is that the discrepancy is even larger at the ToA above the same areas. At the ToA level, the rainforest/wet areas absorb a lot more solar radiation on average than do the desert/dry areas. This evens out upon reaching the surface, which means that something happens in between those two levels. The larger amounts of water vapour and clouds in the ‘wet’ atmosphere simply absorb a lot more of the incoming solar radiation than the mostly water-depleted air in the ‘dry’ atmosphere, preventing it from ever reaching the surface as ‘radiant heat’.
The atmosphere thus lets a lot more solar (SW) heat IN through the ToA (albedo included) above the tropical/subtropical rainforest/wet areas than above the tropical/subtropical desert/dry areas, while letting a lot less terrestrial (LW) heat OUT to space through the ToA.
This is simply how the atmospheric ‘greenhouse effect’ is defined. According to this definition, it is much stronger above the rainforest/wet areas than above the desert/dry areas.
And STILL the sfc temp in the latter areas is significantly higher on average. Completely at odds with (in fact, opposite to) what theory tells us. A stronger ‘atmospheric radiative greenhouse effect’ SHOULD lead to a warmer sfc … ON AVERAGE.
So why doesn’t it? And where is the empirical evidence from the Earth system that it still does somehow?
Does radiative balance determine sfc temp at all? Or are other processes governing it?
https://okulaer.wordpress.com/2014/11/16/the-greenhouse-effect-that-wasnt-part-2/
Kristian,
I provided the answer downthread:
Those dry desert regions that become hottest under insolation despite having least DLR from GHGs and then radiate most to space when insolation stops.
So it isn’t DLR from GHGs that makes those desert surfaces hotter than S-B and there is little DLR from GHGs at night to reduce outward radiation to space.
What makes those surfaces with least DLR the hottest relative to S-B during the day is adiabatic warming of descending air and at night the absence of DLR allows rapid surface cooling such that inversions occur with the ground becoming colder than the descending air above.
Those dry areas with most DLR getting to space directly from the surface are beneath columns of adiabatically warming descending air within semi-permanent high pressure cells.
That perfectly illustrates my contentions that:
i) The ‘extra’ warmth at the surface (above S-B) is caused not by downward radiation but the reconversion of PE to KE as descending air compresses beneath the increasing weight of the atmosphere above as it descends. If that extra surface warmth were caused by downward radiation from GHGs then the colours would be reversed and the warmest surfaces would be beneath the more humid regions (more GHGs).
ii) The kinetic energy available to be extracted at the surface from descending adiabatically warming air is more readily lost directly to space from those desert surfaces due to the lack of GHGs above (dry air) and so as per my previous comments here and elsewhere it is the adiabatic convective overturning cycle that varies so as to readjust the energy escaping to space directly from the surface as compared to that escaping to space from within the atmosphere.
Willis has kindly proved my case with this article and for readers who still don’t understand what I am saying I can only recommend some meteorology studies.
The truth is that GHGs merely reapportion radiation escaping to space between that leaving from the surface and that leaving from within the atmosphere and the mechanism effecting that reapportionment is the adiabatic convective overturning cycle. Both before and after any such reapportionment radiation out to space matches radiation in from space and surface temperatures remain the same despite small variations about the long term average which is set by atmospheric mass and density.
GHGs thus have zero effect on surface temperatures but would have a miniscule effect on atmospheric circulation and the positioning of the climate zones but any such effect is magnitudes smaller than similar effects from solar and oceanic variations
Kristian said:
“the sfc in the dry areas on average heats about the same (from direct solar input),”
No it does not, the surface in drier regions get heated more as there is less atmospheric water vapour present to absorb solar near infrared.
Ulric,
You need to take into account that the desert/dry areas in general lie further from the equator than the rainforest/wet areas, so that the annual mean solar input through the ToA is substantially larger over the latter ones than over the former ones. This equatorial surplus at the ToA, however, is equalized at the surface because of the larger atmospheric absorption (which you correctly point out). Furthermore, the desert surface albedo is much higher than the rainforest surface albedo, offsetting quite a bit of the higher cloud albedo of the rainforest atmosphere.
I am not just throwing out assertions here, Ulric. I base my arguments on the CERES dataset.
Stephen,
You know how I feel about your absurd ‘descending adiabatic heat’ hypothesis. It is just so fundamentally wrong and stupid. So why bother telling me about it even one more time?
I’ve decided to leave you and your ramblings alone (at long last). (Any counter-argument to your self-invented concoctions rolls off like water off a duck’s back anyway.)
Now please grant me the same favour …
Kristian
I know that you think an adiabatic process involves a transfer of heat (as work) between a rising or falling parcel of air and the air in its surroundings.
That is incorrect and if it were correct it would be a diabatic rather than adiabatic process.
The adiabatic process involves work done with or against gravity and not work done against surrounding molecules and so no heat transfers in or out whether via work done or otherwise.
It takes work to lift the mass of a molecule up against the force of gravity and that work converts KE (heat) to PE (not heat) which is then recovered on any subsequent descent.
Roy Spencer referred to descending air warming by subsidence so you have more than me arguing against you. You should also look up Foehn winds and similar phenomena.
I will draw attention to your error for so long as you continue to get it wrong.
If you would just correct that error then the rest of your points fall into place (I agree with most of your narrative but for that error) and you will understand why deserts with few GHGs above them get warmer than humid regions with lots of GHGs above them. As you point out, that is exactly the opposite of AGW theory 🙂
Kristian said:
“This equatorial surplus at the ToA, however, is equalized at the surface because of the larger atmospheric absorption..”
With the amount of cloud albedo on the equatorial belt, it probably does more than equalize. And don’t forget, there are two horse latitudes, and only one equator.
Actually, the interesting part isn’t just what you observed.
Besides the absolute temperatures, one other feature which deserts differ from other land regions is also the relative, if not absolute, lack of vegetation. Semi-facetiously, maybe the reason deserts are so hot is because there aren’t many plants to absorb the solar radiation and to more slowly re-radiate it back because the plants themselves – via their direct consumption of solar energy and the large role of water in the plant life cycle (stomata operation) – affect the energy flow and regulate the water vapor levels.
It would be ironic if global temperatures are actually a function of net plant biomass behavior.
Actually I think vegetation just creates a air gap insulation over the surface, since the ground has a very high heat capacity compared to the atm.
The only reason there are plants there at all is because they absorb the energy and turn it into plants. Plants are endothermic. They also shade the ground by day and insulate it by night.
I like plants. May all deserts be covered with them.
I think main reason why wet equatorial areas are colder than dry desert areas near equator is photosynthesis. As it is endothermic reaction it is removing heat from air and storing it in chemical energy. It looks like photosynthesis efficiency is around 0.1% – 6%. Where typical plants have 0.1% – 2%. Taking average temperature 298K and 2% it means around 6K of removed heat. But plants are only working during day not night, so divide it roughly by 2 and here we are 3K difference why it is colder in wet areas than in dry areas.
Another reason why deserts can get hot during the day is lack of trees. Here in New England, trees evaporate a tremendous amount of water, and that soaks up a huge amount of heat. In fact, the ground here is pretty much saturated from winter to leaf-out. The decline in river runoff when leaves finally come out is striking.
Some desert surfaces have very poor heat conduction, these, especially those at high altitude are notorious for getting cold as soon as the sun goes down and hot when it comes back up. Other areas, like valleys cut through basalt soak up heat all day long and radiate it back to people who thought it would be nice to camp by the river.
Excellent find Willis. What does this tell us about model feedbacks?
If this Brunt method is what is used in climate models, it will mean that water vapour feedbacks are out by factor of two in one direction or the other.
Don’t have time to think it through right now, so I’ll just throw it out.
Thanks, Mike. The Brunt method is not used by the climate models as far as I know.
w.
Thanks, ignore the models part of following, which I posted before reading this.
BTW radiation does not “well up” or “well down” it radiates. 😉
My last home had radiant ceiling heat. People questioned it’s efficiency because as everyone knows “heat rises.”
I only questioned the operating cost of operating electric blankets installed between the joists. The original owners intended to install a small wind turbine on the property but never got around to it or came to their senses.
Mike says: March 28, 2015 at 1:57 am
Ahh, you’re one of those folks who expects English to be logical …
This is what is called a “term of art”, which is a word that used in an unusual manner in a particular profession or trade. If you do a search in climate works for DLR or “downwelling radiation”, you’ll find thousands of examples.
It is used to distinguish between upward-directed radiation that is headed for space, and downward-directed radiation that is headed for the Earth. It’s clear and unambiguous and has been in use with these meanings for years, so I fear you are stuck with it.
My best to you,
w.
Thanks for your cordial reply Willis.
I do not expect the english language to be logical but I do expect it of science and scientific language.
Yes we probably are stuck with it, like we’re stuck with trying to understand a highly complex chaotic system with “linear trends”, like we’re stuck with constant rigging of datasets and were stuck with everything in life being caused by CO2 emissions.
Like we’re stuck with temperature “anomalies” which prejudge any change as being abnormal.
You will also find thousands of references to “downwelling Kelvin waves” which is an oxymoron: Kelvin waves are a surface or boundary phenomenon and as soon at it’s downwelling it’s not a Kelven wave.
Climatology is full of this junk and for the most part is junk science which is why I call it out.
It is not too surprising that this gives a map of water vapour, since it is known that water vapour accounts for about 80% of the total GH effect.
Brunt apparently under-estimates the downward LW over tropical ocean. presumably these a1, a2 values were established way back, a2 would seem to be what could be regarded as the water vapour feedback, meaning it is probably under-estimating WV feedbacks in models.
But the tropics are not warming dramatically, in fact they are dramatically stable. So some other feedback must be compsensating.
The most obvious solution is tropical cloud cover cutting down incoming solar, rendering the tropics highly insensitive to downward longwave radiation.
You will not be surprised by that 😉
Shouldn’t the tropics remain stable since water vapor was already fairly close to a saturation point. Any percentage change would be minimal. My understanding is that the cold dry air of the polar regions is where the amplification would be expected to be most enhanced. But, Antarctic isn’t cooperating.
Just a question.
Tom J:
Humidity percentages would remain somewhat stable. The amount of moisture vapor actually in the air is dependent on temperature; as temperature increases, the atmospheric moisture capacity increases.
ATheoK
Thanks
May be interesting to pull some model water vapour results from KNMI to compare to CERES.
” I used the “Brunt” method, which calculates an “effective emissivity” from the vapor pressure. The vapor pressure in turn is calculated from the surface temperature. I subtracted the satellite observations from the Brunt estimate. Figure 1 shows the result.”
As you say the vapor pressure of water cannot be calculated from the surface temperature. Therefore the Brunt method is wrong. It would be interesting to see the map of the Ceres data alone.
Which Ceres data?
http://ceres.larc.nasa.gov/order_data.php
Paul Berberich March 28, 2015 at 1:58 am
I don’t recall ever saying that. Please provide the quote where I made that claim.
Thanks,
w.
“This is the first time I’ve looked at the difference between a variable in the CERES dataset and an estimate of that variable. They say that all models are wrong, but some are useful. This model of downwelling longwave radiation is obviously wrong … but it’s useful because of exactly where and how much it is wrong.”
Sorry, I interpreted your words that the vapor pressure of water can only be calculated from the surface temperature, if you assume 100 % humidity.
Willis,
Try as I might, I’m not getting the joke. But then I don’t know which Ceres product you’re using, nor what data you used for the Brunt calculations.
the method Willis used assumes water vapor is proportional to surface temperature, but it doesn’t account for the nature of the surface (whether it has water to evorate), thus the mistie between the satellite measurement and theory provides a perfect means to identify dry regions. Brunt is a pretty decent overall method if the mistie is a 0.6 watts per m2 underestimate versus the satellite measurement.
When I saw it I laughed even harder because I realized the Eocene thermal maximum was caused by the shallow oceans that covered areas such as Central Asia and parts of Siberia (and if anybody wants to write a paper about it don’t forget where you got the idea).
Fernando Leanme,
Mmm, that’s not what I’m reading. I used the “Brunt” method, which calculates an “effective emissivity” from the vapor pressure.
Where is the vapor pressure data from? Stokes has dug deeper into it than I have: http://wattsupwiththat.com/2015/03/28/the-desert-finder/#comment-1893207
It’s not at all clear to me that such a method is “perfect”. That’s why I don’t understand joke … it looks to be based on flimsy premises. As well, he’s being ambiguous about which Ceres data product he used: I used surface downwelling clear-sky longwave.
That parameter is available in both the SYN1deg and EBAF-Surface products: http://ceres.larc.nasa.gov/order_data.php
They are NOT the same. A thorough analysis would compare the differences between those two products as well. A seriously thorough analyst might not find anything worth joking about. With Willis, we’ll likely never know.
Brandon Gates March 29, 2015 at 7:32 pm
Thanks, Brandon. The joke was that when I did the analysis I wasn’t expecting a desert finder, or that it would be so amazingly accurate.
As Nick Stokes noted, because I don’t have any gridded global humidity data, I just used the vapor pressure for water at the surface temperature. This seems to be quite accurate where there is surface water, and the deviations from accuracy occur in the dry areas and the very humid areas.
As to whether it’s based on “flimsy premises”, it delineates the deserts better than any other satellite data I know of, and it does so using a dataset with no humidity measurements at all. I find that both surprising and funny, but not “flimsy”.
I apologize for the ambiguity. I thought I was being clear. I’ve never used or discussed anything but the EBAF CERES dataset, so I didn’t think to identify it as the EBAF dataset.
I fear I don’t see that a comparison of the two products would show anything of value. If you think there is something there, the data and I await your serious and thorough analysis. Me, I tend to dig where I think there might be gold.
My best to you,
w.
OTOH, I looked at the image before reading much more than the title and wondered why Willis included an image of desert and moist areas. I hate humidity, I’m not going to visit the Amazon!
Willis
Ceres provides a product, not raw data.. I am curious about which product you used.
Thanks, Alex. I used surface downwelling clear-sky longwave.
w.
Thanks
You did not mention the timescale of the CERES data. Looking at the link that you provided in an earlier article (Feb15th 2015) the latest set is for mid 2014 it seems to me . But some of the datasets go back 15 years , so could your latest technique be applied to see if there is a change in the “greening ” of desert areas over the last decade or so ?.
Willis,
It’s not clear to me what data you used for the vapor pressure e in the Brunt expression. According to your linked paper, e is not the saturated vapor pressure, but has to be multiplied by the locally measured relative humidity, which of course would be low in desert regions. Did you do that?
Nick, according to the linked paper,
I don’t see anything in there about relative humidity … what am I missing.
w.
Willis,
Look at eq 13, p 882, and the surrounding para. Sat wv pressure is denoted e_s; to get e, you multiply by RH, as in eq 13.
ps sorry about he delays. For some reason, since about the start of 2015, all my comments go through moderation.
My first guess would be that they assumed saturation, i.e., 100% relative humidity.
I would assume that vater vapor pressure is just another way of saying the dew point. From the dew point or water vapor pressure one can know, calculuate the parts per million of water vapor in the air. This is a graft created using the goff-graph equation. http://toms.homeip.net/global_warming/SpreadSheets/Goff-Gratch-ppm-h20.gif
At a dew point of 70F there are only 25,000 parts of h20 per million. Competing with the 100 ppm of CO2 increase over the last century.
“My first guess would be that they assumed saturation, i.e., 100% relative humidity.”,
Well, the linked paper didn’t:
“relative humidity and air temperature were measured by means of an HMP35AC solid-state probe (Campbell Scientific, Inc.)”
But Willis seems to have. I think that is why the deserts show out as discrepancies.
An interesting read as usual, thanks. Here is my limited take on the subject.
If ‘greenhouse gases’ are absorbing energy from the sun then that ‘absorbed’ energy never reached the surface. Seems reasonable the absorbed energy warmed the atmosphere but THAT energy is no longer available to be included in the DLR. As I understand it, only half the energy emitted by ‘greenhouse gas molecules’ in the atmosphere can reach the surface. I have read reports that less than half reaches the surface depending on the altitude of the gas. This all looks to me like a day time cooling effect.
Clouds have a marked effect on local temperature.
Many times I have noted, after a warm clear sunny day, the early night time temperature drops sharply. If a bank of cloud moves in during the night the temperature rises. This rise in temperature can approach the daytime temperature but I have not seen it exceed the day time temperature. This looks to me as a clear example of ‘back radiation’ from the cloud base reducing the radiation cooling of the surface which allows heat stored during the day to reach the surface and the night time temperature to rise.
“This all looks to me like a day time cooling effect.”
Way back when I started questioning “Co2 drives the climate” thing, I compared average highs and lows between Shreveport, LA and Yuma, AZ and came to the same conclusion. During the day time our atmosphere act like a swamp cooler. On average Shreveport was 15 degrees cooler than Yuma. At night there wasn’t more 5 degrees difference in lows, Yuma being warmer. That’s when I knew that “CO2 drives the climate” was nothing more than a political driven agenda.
old construction worker
March 28, 2015 at 3:57 am
That’s when I knew that “CO2 drives the climate” was nothing more than a political driven agenda.
——————-
As far as I can tell there is no any such agenda there, politically or otherwise driven.
If your refer to AGW,, again as far as I can tell, it has nothing in connection with CO2 been a climate driver. Actually in contrary, in the AGW point of view CO2 is a climate changer at the such high modern CO2 emissions in the anthropogenic era and it is an amplifier of warming as far as considered in the long past term of natural climate.
In both these cases CO2 is not considered as a driver of climate change.
As a driver in principle the CO2 will mean an effect that drives and assist climate change, but it does not cause it. It means that it will drive (accommodate and help towards better efficiency) the climate through its variation, through warming and cooling also, especially in the turn of the trends, at the famous points of the lags…….
Just saying for the sake of terminology.
From my point of view the problem is that the RF (CO2,,, Greenhouse effect) are not really considered in the angle of it been a climate driver, not seriously.
cheers
Catch 22
Catch CO22, surely?
Yes, the Moon demonstrates that the effect of an atmosphere is moderating: reducing the maximum temperatures and raising the minimums.
At last there is proof that man’s emissions of CO₂ are affecting the global temperature. As the CO₂ level goes up, the deserts are greening and the DLR increases, sorted.
What this seems to tell us is that water vapour is the overwhelming major medium of energy interchange in the climate. And yet it is completely ignored by the Alarmists….
This is roughly akin to architects suddenly getting concerned about the buoyancy of buildings (which displace air, of course) and insisting on adding this to all weight and stress calculations which are done. Then panicking over the fact that during low-pressure episodes the building’s buoyancy could change drastically, resulting in building collapse…..
Hey! I’ve just invented a new reason for getting grants…..
Hilarious Willis – where is the “dominant CO2” effect? 🙂
I wish that Willis would use his talents to look at some of the iconic CAGW issues. Like another look at humidity, the hot spot, Mann’s HS, temp adjustments, arctic/ Antarctic ice, sea level rise, extreme weather events etc.
How do the above compare up to 1950 and since 1950, because this is the IPCC’s date for impact from co2 emissions. Just asking. BTW I’m sure I’ve missed a number of the more cherished icons of the alarmists. How about it Willis, even one a week or so would be good?
Neville, I’ve looked at many of those, including Mann’s work, the “hot spot”, arctic and antarctic ice, and sea level rise.
w.
Neville:
Why don’t YOU look into it?
Willis looks into the things that fascinate him, as it should be. Life is too short to do what other people want you to do…
Some of the greatest DLR comes from areas where there are great rivers in the Northern parts of South America. One has to wonder what impact irrigation has had on the earth’s climate. Modern large scale irrigation must have produced sustained increases in DLR in (land) areas that otherwise would have freely radiated much more towards space, thus moderating temperature. Particularly at night…
Let’s hope that the CAGW crowd does not begin to include water vapor among their list of greenhouse gasses to regulate. I can just see them lobbying to ban all man-made forms of irrigation. After all, it would fit the left’s agenda to decrease the Earth’s population.
NOAA –
I certainly hope you are not logging in with a traceable identity (like wordpress…).
Tim, John Christy has a good paper on the effect of irrigation on the weather around the central valley in California. Sorry, no link to hand.
w.
That would be this paper…
http://journals.ametsoc.org/doi/abs/10.1175/JCLI3627.1
Abstract
A procedure is described to construct time series of regional surface temperatures and is then applied to interior central California stations to test the hypothesis that century-scale trend differences between irrigated and nonirrigated regions may be identified. The procedure requires documentation of every point in time at which a discontinuity in a station record may have occurred through (a) the examination of metadata forms (e.g., station moves) and (b) simple statistical tests. From this “homogeneous segments” of temperature records for each station are defined. Biases are determined for each segment relative to all others through a method employing mathematical graph theory. The debiased segments are then merged, forming a complete regional time series. Time series of daily maximum and minimum temperatures for stations in the irrigated San Joaquin Valley (Valley) and nearby nonirrigated Sierra Nevada (Sierra) were generated for 1910–2003. Results show that twentieth-century Valley minimum temperatures are warming at a highly significant rate in all seasons, being greatest in summer and fall (> +0.25°C decade−1). The Valley trend of annual mean temperatures is +0.07° ± 0.07°C decade−1. Sierra summer and fall minimum temperatures appear to be cooling, but at a less significant rate, while the trend of annual mean Sierra temperatures is an unremarkable −0.02° ± 0.10°C decade−1. A working hypothesis is that the relative positive trends in Valley minus Sierra minima (>0.4°C decade−1 for summer and fall) are related to the altered surface environment brought about by the growth of irrigated agriculture, essentially changing a high-albedo desert into a darker, moister, vegetated plain.
And their hypothesis appears to be that all of the warming in the region can be attributed to irrigation (and other land based changes) but it seems to me that there are far too many assumptions to be of any real use in that regard.
This theory appears to be not correct — look at any standard meteorological text books Also, sea breeze, land breeze theories, etc. Irrigated zone should follow cold-island effect and non-irrigated zone should follow heat-island effect.
Dr. S. Jeevananda Reddy
If someone in northern BC or AB wants a research project on water affecting local climate, there’s the very large lake created behind a power dam on the Peace River, circa 1960s. http://en.wikipedia.org/wiki/Williston_Lake
I expect that storage increased evaporation there, whereas normally the water would have flowed into northern AB then on to the Arctic Ocean, perhaps with more evaporation along the way due to higher water levels in lakes but less overall (presuming less in the Arctic as it is colder). I presume there’d be more water flow in winter due to release from the dam for power generation.
Locals claim the climate is wetter there now, and that growing hay for seed has replaced grain crops.
However, that could be due in part to climate variation and to more clever farming.
(Growing what works better more often. Wheat can be chancy there due risk of early snow before harvested, IIRC barley and oats were grown often but dry years were a problem. Choice of crops even depends on how many animals are raised – I have names of cattle farmers downwind of the lake, they probably know some in the Chetwynd area which is south of the lake.
I presented a series of equations to estimate precipitable water, global solar and net radiation in 70s-80s:
Rt [global solar radiation] = a x L x [square root of saturated water vapour];
Rt = a + b x [la] + c [cube root of precipitation in mm]
Rn [net radiation] = b x L x [wet bulb temperature in degrees Celsius];
W [precipitable water vapour, gm/square cm] = c [square of Wet bulb temperature in degrees Celsius];
Dr. S. Jeevananda Reddy
I think it needs to be remembered that evaporating each Kg of Water absorbs 2.2 KJ of heat which it also radiates to space. High levels of evaporation extracts heat energy from the surface which is why oceanic regions are so much cooler than deserts, so while DLR may be larger, the Nett effect is to cool during the day, and heat at night. That is water vapour moderates extremes.
At night you can see rel humidity increase as it cools, at higher values water starts to condense out, tte heat that water has to give up, slows cooling, but it also drys the air. In the morning any water not lost the environment evaporates back out as it warms. But this process regulates both temps and humidity.
Up a ways you asked about how air gives up heat when it cannot emit infrared. Gases such as nitrogen give up energy by physical contact to molecules of carbon dioxide, methane or water which CAN then emit infrared. In this sense, more carbon dioxide improves “top of atmosphere” cooling by becoming a more effective radiator, but it also retains more heat at the surface. This increases the vertical gradient which in turn would usually provoke more convection.
“…water vapour moderates extremes [in temperatures].”
Yes – consider the moon: -233 C to +123 C
And how much does that range varies over time? 🙂
cheers
The energy needed to evaporate surface is cooled during the day, but water vapor due to the large heat capacity reduces the vertical temperature gradien atmosphere. Water vapor due to the high heat capacity also collected heat energy directly from the sun during the day, as seen in the following graphic.
http://www.ospo.noaa.gov/data/atmosphere/radbud/gs19_prd.gif
Unclear.
The amount of water vapor at a height of 5 km.
http://www.ospo.noaa.gov/data/mirs/mirs_images/n19_wv_500mb_des.png
You can see that the water vapor over continents absorbs solar radiation.
My quick estimate for the world’s tallest building suggests that its buoyancy in air is about 2,000 tons. That surprised me – I would have thought it was less. It’s still around 0.00001 of total weight, so the comparison with CO2 concern still stands…
That would be if the building was a sealed prism with no air inside?
Dodgy, a truly great and appropriate analogy…
Wicked, you are correct…
“In the desert the air is so dry that more radiation escapes to space, and less is absorbed and radiated downwards (and upwards) by the atmosphere”
Not according to JMA
http://ds.data.jma.go.jp/gmd/jra/atlas/eng/indexe_surface12.htm
http://ds.data.jma.go.jp/gmd/jra/atlas/column-1/pwat_ANN.png
http://ds.data.jma.go.jp/gmd/jra/atlas/surface-0/dlrsfc0_ANN.png
This is just the measurements or the estimates. The equatorial areas will give off more as they receive the most direct sun every day. Willis subtracted the measurements from the estimates to gauge accuracy of said estimates. The estimates are way too high for the arid areas in the desert belts. They are also too low for the tropics. — John M Reynolds
Sorry, By “this” I mean the JMA graphs you posted.
So the DLR follows the precipitation ?
lgl
Those charts show that most DLR is directed downward in the more humid regions.
That is consistent with Willis’s chart that shows least DLR in the dry desert regions.
Yet it is those dry desert regions that become hottest under insolation and then radiate most to space when insolation stops.
So it isn’t DLR that makes those desert surfaces hotter than S-B and there is little DLR at night to reduce outward radiation to space.
What makes those surfaces with least DLR the hottest relative to S-B during the day is adiabatic warming of descending air and at night the absence of DLR allows rapid surface cooling such that inversions occur with the ground becoming colder than the descending air above.
2/3 of the energy to the surface in ‘dry’ places is DLR
http://www.esrl.noaa.gov/gmd/webdata/tmp/surfrad_5516c4f96bf1f.png
lgl,
Why do locations receiving 2 thirds of their energy as DLR get hotter than locations receiving more of their energy as DLR?
Where do you think that DLR in regions with few GHGs comes from ?
I say it comes from the adiabatically warmed molecules closest to the surface and not from GHGs at all.
lgl commented
This energy is stored in the ground, not the air. It’d be nice to see the rest of the data for these measurements, like what was the humidity, even low rel humidity could have a lot of water, and the ground is going to be radiating which water and Co2 will return, but the amount of SW going up and the amount due to water are critical to understanding.
I think many people don’t distinguish these parameters, because when you say the total average of 3.2W/m2 is tiny compared to the other parameters, plus we don’t know that it’s wholly contained by the energy bounds of atm water (as the station graph I posted shows actually happens).
Thanks lgl,
two links: the japanese realise that radiation is “downwards
long wave”
http://ds.data.jma.go.jp/gmd/jra/atlas/surface-0/dlrsfc0_ANN.png
NOAA don’t know shit and think infrared radiation can be “downwelling”
http://www.esrl.noaa.gov/gmd/webdata/tmp/surfrad_5516c4f96bf1f.png
Jeezus, water may well up, radiation radiates, it does not “well” up or down.
Stephen
Almost all DLR comes from GHGs (and clouds, but there are none in the plot from Nevada).
There is almost no DLR coming from your adiabatically warmed N2 and O2 molecules.
The only regions with “few GHGs” are the polar regions, where there is also little DLR.
There is more vapor above the Sahara and Australia than above Europe and the US for instance
lgl
You accept that there is little in the way of GHGs above deserts.
Yet deserts reach temperatures higher above S-B than do humid areas with more GHGs.
Why do you think that happens ?
It can only be because of adiabatically warmed descending air.
Hence it is that descending air that causes the ‘extra’ 33C at the Earth’s surface and not downward radiation from GHGs.
It does it because the thermal capacity of dry air is significantly lower than humid air.
I should add that the ‘extra’ warmth at the surface of deserts is achieved via sunlight PLUS restraint of convection by the descending air column and not by the DLR that is received.
If DLR had a warming effect then one would see higher surface temperatures above humid regions than above dry regions.
Stephen
Perhaps you should look up adiabatic, “taking place without loss or gain of heat”. An adiabatic process can’t heat the surface, DLR can.
lgl
“An adiabatic process is one that occurs without transfer of heat or matter between a system and its surroundings”
http://en.wikipedia.org/wiki/Adiabatic_process
I have come across various misunderstandings of adiabatic processes and yours is one of them.
During uplift and descent no transfer of heat occurs between the rising and fgalling parcel of air and the surrounding air.
Instead, energy within the parcel is transformed from KE (heat) to PE (not heat) during uplift and the reverse on the descent.
Stephen
Exactly, “within the parcel”. So you agree the adiabatic warming does not warm the surface then?
Adiabatic warming of descending air warms the surface indirectly in two ways:
i) Clouds dissipate so more sunshine hits the surface. Similarly a glass greenhouse roof being transparent allows sunshine in.
ii) The descending air inhibits convection from the surface so that surface temperature can then rise above S-B. Similarly a glass greenhouse roof inhibits convection.
The greenhouse effect is aptly named but it is a product of atmospheric mass and not radiation.
Stephen
“inhibits convection”?
Air is descending because air is ascending at another place. This process does not add any energy to the surface, and it is the energy balance at the surface that sets the temperature. And I have shown there is a lot of DLR at night, so still all wrong.
lgl
There is less convection beneath a high pressure cell (which is by definition a column of descending air warming adiabatically) than there is beneath a low pressure cell.
The overall radiative energy balance is maintained by the interaction between adiabatic uplift and adiabatic descent.
If there are no radiative gases all incoming energy from the sun departs back to space from the surface and in that situation energy taken up in uplift matches energy returned towards the surface in descent.
If one adds radiative gases then radiation to space from within the atmosphere then becomes possible and energy returned towards the surface in descent falls short of energy taken up in ascent.
That reduction in energy returning to the surface offsets what would otherwise have been a surface warming effect from the radiative gases.
Surface temperature stays the same but the air circulation changes instead with more energy leaving to space from within the atmosphere, less leaving from the surface direct to space and the radiative balance maintained overall.
Ok, how much DLR when the sky Is -70F?
Stephen,
wrong wrong wrong. Adiabatic means there is no energy “taken up in uplift” or “energy returning to the surface”. The only ‘uplifted’ energy is latent heat, and some of that is lost to space and some is returned to the surface as DLR.
lgl
The term adiabatic is limited to ascent or descent after initial lift off or before the lowest point of the descent.
The initial lift off is caused by diabatic solar heating of the surface. Only after that initial event does the continuing ascent become adiabatic.
When the warmed air descends to its lowest point (which need not be the surface if an inversion is present) then it indirectly causes enhanced diabatic heating of the surface by dissipating clouds and inhibiting convection.
The term latent heat is limited to the (non thermal) energy carried by the vapour form of water.
That term does not cover the transformation of KE to PE or PE to KE when work is done against or with gravity in the adiabatic process.
You have some serious thinking to do if you are to overcome the conceptual flaws in your understanding.
Stephen
Serious thinking probably won’y help in your case. You will have to learn some physics.
ROFL
lgl
If the N and O2 heat the CO2 via molecular vibrations, will the CO2 then have the ability to issue a photon as long wave radiation? If so, then SWs explanation holds true imo.
lgl, SW gave you the correct definition of “Adiabatic”, so I won’t repeat it. Your statement here indicates that you don’t understand how physical transport affects heat transfer. For example, rain falling is physically transferring heat away from the surface as energy is transferred from warm surface to cold water. Similarly, warm air rising is physically transferring energy away from the surface without involving radiation or conduction. Cooler air is pulled in from the side, which is then warmed and rises.
The air closest to the surface is typically in near thermal equilibrium with the surface. The surface is heated by solar radiation, and the surface temperature rise is not just limited by the air, but by the thermal conductivity and heat capacity of the land or water. As the surface temperature rises, the low heat capacity air (right above the surface) follows in lock step.
This triggers a delta T between this air and air higher up. Lower air heats higher air, but is then immediately heated by the surface, as soon as any delta T opens up between the surface and the lowest air. When one places one’s hand on a large marble structure, the difference in heat capacity means that our hand cools quickly, while the marble structure temperature drops infinitesimally. Similarly, the hot surface can easily keep the air in near thermal equilibrium.
When solar radiation stops, heat is drained from the surface in multiple ways. An important (but often forgotten) way is that heat is conducted away by land and/or sea. Even if there was no other way for the surface to lose energy, this alone would result in a cooling atmosphere, as the air temperature near the surface would still stay in lock step with the cooling surface. Of course, energy is also drained into the rapidly cooling atmosphere.
I believe that SW’s point was that over a desert, with a parked high pressure zone, no rain, air rising slows, convection is diminished, the surface will heat up more, limited only by thermal conductivity of the surface. Sounds reasonable.
Convection is radiation/conduction over and over again. That’s why convection dominates in the Troposphere. An atmosphere of only N2 and O2 would be a poor conductor of heat. Adding water vapor and C02 increases thermal conductivity, transferring heat from the surface easier. It’s unreasonable to think that this would result in a higher surface temperature.
I think Clive Best explains it well:
Viking
you can start here, http://www.climate.be/textbook/chapter2_node8.xml
I wonder how did the map look like after you used your fitted values. I guess it wasn’t map of water vapor anymore.
Huh?
its buoyancy in air is about 2,000 tons.
===========
the mass of a hot air balloon is about 4 tons.
A couple observations, it says a lot about GH effect because you can see that it’s water vapor that regulates nightly cooling, as it cools, rel humidity goes up and cooling slows down above~80%, this shows that effect, but I’m suspect on the polar areas, downwelling IR has to be mostly from surface temps, and at- 40F, there isn’t a lot of upwelling IR to be reflected back.