The Cloud Radiative Effect, Take Two

DonV says:
October 5, 2013 at 4:58 pm
Don I discuss some of the energy transfer here:
http://wattsupwiththat.com/2013/10/03/the-cloud-radiative-effect-cre/#comment-1435512
Heavy rain at 1″ per hour is 15,924 W/m^2 of surface area. Kind of a lot…
I was thinking about how much more surface area the cloud top must have to radiate away enough energy to balance the 15,924 W/m^2 of heat released during heavy (1″ per hour) rain. I only assumed condensation to a liquid, used a typical water droplet diameter of 0.02mm, and cumulonimbus water content of 2g/m^3. Given that, the cloud top “surface” should radiate at around 31 W/m^2. This indicates the surface area needs to be about 515x the size of the 1 m^2 that is raining at 1″ per hour to dissipate that much heat. So if it is raining that fast on 1m^2, the cloud radius at the top would have to be 12.8m so support that much energy dissipation (assuming no GHG above that). Actually, if the storm was this big, freezing would be occurring, and at 50,000 feet the temperature would be more like -57°C, and radiation would only be around 12W/m^2 of cloud “surface” and the storm diameter ratio would go to 20x. At that level, there is only about 10% of GHG’s above the storm, I didn’t account for this either.
droplet dia 0.02 mm
droplet radius 0.01 mm
droplet area 0.001256637 mm^2
droplet area 1.25664E-09 m^2
droplet volume 4.18879E-06 mm^3
droplet volume 4.18879E-15 m^3
droplet volume 4.18879E-09 cm^3
Cumulonimbus g/m^3 2
n droplets/m^3 477464829.3 per m^3
surface area all droplets 0.6 m^2
W/m^2 at 0°C H2O IR emission 309.3445884
Watts/m^3 185.6067531
surfaces on m^3 6
watts per surface 30.93445884
w/m^2 raining 1″/hr 15924
surface area of cloud top 514.765753 m^2 per m^2 rain
cloud top radius 12.80058703 m per m rain
Just a first shot at estimating radiation from cloud tops. It depends very much on a lot of factors – I just used some averages and assumed 0°C.

Hi Willis,
temperature change may affect cloud cover, but cloud cover change also effects temerature.
How do you separate cause and effect ?

JKrob says:” All of this is basically true but what was left out was that the descending air is warming at the dry adiabatic rate as it falls which counteracts the cooling issue.”
It’s always colder after a mid-afternoon summer/tropical thunderstorm. A lot of heat goes up in the form of warm moist air and the only thing that comes back down is drier cooler air plus cold rain so what is the counteraction?

Bill 2 says:
October 5, 2013 at 6:55 pm
As dbstealey says at 7:59 pm, “If there is a problem with the description given, please identify the problem. Don’t just appeal to a vague authority that cannot be easily checked by readers.”
Because at least 2 of us don’t see in your comment at 6:55 what you seem to think is clear.
From the following link:
http://www.exploringnature.org/db/detail.php?dbID=112&detID=2633
“As the clouds rise into the colder atmosphere, the water droplets come together and get bigger and heavier. Finally they will begin to fall. As they fall, they pull air with them. This is called a downdraft. ”
and . . .
“The thunderstorm downdraft can bring a gust of cool air to the Earth’s surface. This is called a gust front.”
Drawing here:
http://www.srh.noaa.gov/jetstream/tstorms/wind.htm

Willis,
Have you ever thought about the hygroscopic effects of exposed salt on the ground, and cloud formation of (e.g., lack of). The areas of exposed salt are: Lake Uyuni, Bolivia; Great Salt Lake, Death Valley (+other areas in Nevada and Utah); Lakes Eyre, Frome, and Torrens, in Australia; The Dry Valleys of Antarctica (are probably dry because any snow falling there dries out (melts) because of ground salt); The Kavir of Iran; northern Algeria; parts of Marokko; East African Rift lakes (Magadi,etc), Quattara Depression, Egypt; Baluchistan in Pakistan, etc, etc.
You see, these dry and very salt locations are also those areas of the terrestrial earth that are lowest in elevation (probably due to mineral corrosion – i.e., dust formation by the aggressive salt). I guess some of the fine salt particles find their way into the above atmosphere and prevents droplet formation – very little rain…?
All the best MH

@AndyG55
I think he made a model and had it peer reviewed and improved it based on the feedback received. I call it ‘science’.
@Fred Souder says:
“Condensation in clouds adds a LOT of energy to the air. Of course, you maintain that this energy is more easily transmitted to space, which I believe is true.”
Well, it is all transmitted to space eventually. Every last Joule. So we are really investigating the retention of energy at some point in the vertical scale until it is effectively radiated into space. That is why they use of the concept of a ‘height’ at which the heat effectively leaves us forever. A change in GHG’s like water vapour changes the ‘effective height’ which is an average, and thus may miss the ‘punch through’ of a rising thunderhead that creates instead a very bright spot of IR far above the supposed average altitude. Does thunderstorm punch-through dominate heat loss, or GHG’s providing insulation?
It is worth considering the comments on this subject made by Prof Adrian Bejan, the author of numerous heat transfer textbooks. His comment with regard to the efficiency of rising heat columns (which form naturally if there is spot heating below) is that the vertical transport of heat energy takes place at the maximum efficiency possible, never going faster upwards at a speed that induces turbulent flow. Thus the centre rises faster than the space immediately around it which in turn is faster than the space around that, etc, until the toroidal flow is a cell large enough (governed by the viscosity of the air) to break into concentric cells with opposing flows. That happens in a hurricane which is why as it passes over, it rains like hell for a while then stops, only to be repeated in waves hour after hour. Each rainfall is a cell connected to the others on its outer surface.
Bejan’s point is that discrete cells form naturally and operate at their most efficient possible heat transport rate. If the surface warms slightly, the column is slightly larger in diameter and it dumps the heat upward more efficiently because everything within the system is moving vertically as efficiently as possible. Where this not the case, large thunderstorms would not cool more efficiently than small ones.
The model of this is two horizontal plates, the lower one being heated from below, and a convective medium moving heat from the lower to the top, colder plate. When the plates are near each other, as is the case when looking at the atmosphere in cross section, cells develop automatically with connected toroidal flows, and they dump heat as efficiently as possible to the cold plate. Heating the bottom plate slightly more does not result is a much warmer region immediately above the bottom plate. It just increases the heat flux rate to the plate above. If the temperature is varied a lot, the cell structure adjusts into square, hexagonal and other patterns. It is amazing and he explains the math involved. The fact that the top plate is cooled by IR radiation into space is irrelevant. It is just how things work on the case of a planet.
Bejan said that the problem was so simple to solve it was not even interesting.
Anything that adds heat to the bottom increases the efficiency of heat transport. Because clouds are a complication, they strongly affect several aspects how the heat gets to the surface or not. Myself, I am holding out that Svensmark is correct about clouds and Bejan is correct about self governing heat transport mechanisms. Together they show the Earth has a strong self-governing, damped temperature regulating mechanism that is happy to stabilize for long periods at any average temperatures from a balmy Arctic to a frozen Virginia. The real controls are outside the system.

As I have said before, we live in a big swamp cooler

This week’s New Scientist magazine vol. 220, no. 2937, 5 October 2013, has a special report on climate outcomes in the wake of the IPCC report, plus an editorial and a couple of very short articles that are also on the climate. One of those short articles (on page 17) is about the large fall in CO2 emissions in what was the USSR after the collapse of communism. The article does not actually say that all we need now is a collapse of capitalism and the global warming problem will be solved!
The other short article, Climate Science Tweaked, on page 6 is more relevant to Willis’s post on clouds – but comes to the opposite conclusion. The final paragraph states:
Clouds are also a menace. In 2007, it was uncertain whether clouds cooled or warmed the planet overall. “We now believe that they are a positive feedback on temperature,” says Piers Forster of the University of Leeds, UK. “Their warming effect will intensify with global warming.”
I wonder what Willis Eschenbach makes of the claim that clouds have a positive feedback effect on temperature?

JKrob says:
Jeff, thank you for the feedback. I learned a lot from your discussion and it was very informative and welcomed. Thanks for the education.
However, I noted several things in your discussion that do not jibe with my own observations what I see when I watch a storm, and my own knowledge of what I know happens in cooling towers and water based evaporators.
First things first:
“A colder surface cannot warm a warmer surface.” This statement by itself is essentially true. But I believe you are missing something important. . . . while the laws of thermodynamics state that NET energy balance between a cold radiator and a warmer radiator will have the warmer radiator transferring net energy to the colder – 1) it does NOT mean that radiation does not OCCUR in the opposite direction. The cooling of one black body radiator at a lower level to a cooler state MUST create an IR signature that indicates its black body temperature. You are correct that as you ascend into a cloud this IR signature changes as the temperature changes. But at each incremental foot up, the droplets of water that are cooling and radiating this energy DO NOT care whether they are radiating towards a warmer body or the colder layer of water droplets above them or the very very cold of outer space. They simply radiate! What is REALLY important is whether these radiating water droplets are warmer than the AIR around them. They MUST BE IR brighter if they can be SEEN with an IR imager. So 2) the NET transport of energy between clear dry air, and water vapor, droplet, ice saturated air is orders of magnitude greater in favor of the later. So yes at 1000 feet ASL a thunder cloud is transferring energy out at that level because the water at that level is initially warmer, but gives up an enormous amount of energy as it phase transitions. 3) Any radiative energy that shines back down from just cooled water droplets to warmer water vapor saturated air coming up must be simply absorbed and added to the upwelling water vapor energy content. Any that radiates up throught the cloud does also, but instead into water droplets. And any that are close to the clear edge radiate to outer space or, if we had one, our tuneable IR camera. And finally 4) I believe the “continous process” you speak of is the loss of sensible heat, not latent heat. Latent heat loss occurs at one temperature/pressure transition. It is discontinuous and often quite sudden. Sensible heat loss, the cooling of water droplets or water vapor or ice crystals AFTER phase transition can be continuous and does most likely occur throughout the transport of water up through a cloud, but it is orders of magnitude lower than latent heat loss.
Now you also state:
“Clouds, in whatever shape or form, emit IR at whatever temperature the level of the cloud is at. This is especially evident with cumulus clouds. If you were to observe the vertical tower with an IR imager, you would see a thermal gradient up the side of the cloud with warmest at the base & coldest at the top and the top growing colder as it grows higher.” Again, parts of this statement are essentially true, but they are also combined with pure conjecture. More importantly the combined statement it ignores the important salient point I raised in my statement of theory. At each elevation the standard black body radiation curve must match the local temperature of whatever molecules are present. I posit that when water, 1) first as vapor, then 2) as water droplets, then 3) as ice crystals are present at any given elevation, the local black body temperature that creates the local IR signature will ALWAYS be greater than when compared to clear air. Hence water is serving as an energy transport medium. Second, it is not the IR signature spectrum that is important (the IR signature spectrum is what indicates the local black body temp), rather it is the INTENSITY of RADIATION at that signature that tells whether a significant energy loss is occurring. You mention “No, as the parcels are lifted higher into the atmosphere, they cool & get ‘dimmer’ (less IR energy) not warmer & ‘brighter’ (more IR energy).” By “dimmer” and “brighter” what I believe you mean is that the whole black body radiation curve shifts to longer and longer wavelength, where the outer tropopause has the coolest IR signature. But again, relative to what? If ice crystalizaion or sublimation is occuring then it MUST have a greater INTENSITY at that local IR signature when compared to normal cooling of the surrounding nitrogen or oxygen gases, (very little CO2 at this level, too heavy). The evidence for this would be a comparative IR picture, comparing the normal IR signature INTENSITY of the normal lapse rate of a low relative humidity clear air column side by side to the same IR signature INTENSITY of a storm cloud. My theory is that at the level at which condensation is occuring and then again at the elevation where most of the freezing is occuring you will see an very large difference in the IR radiation INTENSITY at that particular IR black body signature spectrum. You will also see a somewhat less intense IR radiation signal that is still significantly greater than clear air that is due to sensible heat loss, because water has a higher heat capacity than air.
And finally you state:
“No, the process of condensation from lift, as well as the associated release of latent heat, is a continuous process regardless if the process is going from gas to liquid, liquid to solid or gas to solid. It’s all as seamless, continuous process in a towering cumulus cloud.” This statement does not match what I SEE from the side of a towering thunder cloud. I SEE a discontinuous process. I SEE at least two distinct layers. I SEE a layer where water vapor has formed into water droplets. Therefore the evidence from my eyes tells me that at that layer condensation is rapidly occuring, Therefore, I presume that the local temp and pressure at that layer must have created the conditions for supersaturation, and therefore at that layer and NOT BELOW IT one might expect to see greater IR intensity at whatever local black body radiation temperature might be. Next, I only SEE cloud billowing up from below. What I don’t SEE is a uniform and sudden appearance of cloud all the way from the first layer up to the second! Therefore I SEE condensation only where water vapor has “punched” through the already saturated cloud, (where no further condensation is occurring) but where local conditions still favor the liquid phase of water not the gaseous phase or the solid phase. The P and T conditions that favor condensation occur all the way up to where I SEE what I believe to be the next “layer”, which is where now the conditions favor freezing and ice crystal formation – the anvil “head” of the thundercloud. When that occurs, again compared to what energy is contained in the black body radiator surround each droplet to ice transition, the NET IR radiation HAS to be from the phase transition event OUT to the local air and hence its IR radiative INTENSITY at that local black body radiation spectrum MUST be higher than when compared to clear dry air.
At this point, I will repeat what “otsar” asked: “Has anyone actually scanned a cumulonibus from top to bottom, from the side, with a wideband IR spectrometer? Mapped a cumulonimbus from the top and from the bottom for the wavelengths present?”
And I will add, How does that spectrum with intensity variation compare to clear dry air? If such a “picture” exists, I would like to see it. That kind of “picture” would show me the data and give me a clearer understanding of the processes.
Finally, I am NOT “confused by the different color enhancements made”. The picture I saw had no such enhancements (at least that is what the description claimed). And what I noticed about the picture was the very blackness of the ocean around the storm. This to me indicated that the INTENSITY of the OLR signature for the “balancing act” is significantly greater for clouds and the water cycle than for non-water GHG processes.
Again, respect to you Jeff, Tallbloke, otsar, etc. and Willis for this discussion. Educate me some more. I love this discussion.

@DonV
You commented to JKrob
>First things first:
>>“A colder surface cannot warm a warmer surface.” This statement by itself is essentially true.
There is frequently confusion about the difference between a cold object heating a warmer object by conduction and energy exchange by radiation. It is frequently raised in debates about heat transfer and the root problem is how science is taught in high school (badly and incompletely and with poor retention).
Radiation from all objects transfers heat to all other bodies all the time whether they are they same temperature or not. Conduction is another matter entirely. It may surprise people to know that their skin is cooled by the walls of their house by conduction through air, though the energy moved is tiny.
Cold objects cannot warming a hot object by conduction, but they certainly radiate energy towards them in an unequal fashion, eventually gaining more from the hot object than they lose in return.
What you said is correct – plus some sensible things far above.