Cementafriends comment

[Sunsettommy]

From HERE

Quote:cementafriend
June 21, 2012 at 12:10 pm · Reply

As an engineer with some experience in heat transfer, I go along with EM Smith (Chiefio) in not agreeing with the 1.2C climate sensitivity. I have commented a number of times that it appears no climate (pseudo)scientist and most physicists have little or no understanding of thermodynamics, heat and mass transfer, fluid dynamic or reaction kinetics because they have had no actual experience (such as measurements, process control, equipment design etc). If they understood heat transfer they would know that there are four types which affect surfaces a) conduction b) convection c) radiation and d) phase change. They would know that the Stefan-Boltzmann equation applies to surfaces in a vacuum without some mathematical assumptions and manipulations. When there is an fluid (eg air or water) over a surface other heat transfer mechanisms occur at the same time. If they understood simple technology they would also understand that a gas does not have a surface. CO2 is a gas which absorbs radiant energy over a very narrow wavelength and over a path length. The internationally acclaimed Chemical Engineer Hoyt Hottel developed graphs and equations involving path length to heat transfer from and to combustion gases from actual measurements in the range 100F to 10,000F. From the latter it can be determined that the radiant absorption of CO2 at the present level in the atmosphere (say 400ppm) is insignificant.

[Derek]

I have replied on the thread at Jo Nova's to the comment as follows.

" If they understood heat transfer they would know that there are four types which affect surfaces
a) conduction b) convection c) radiation and d) phase change. "

Excellent point, and the order of importance is???
http://www.globalwarmingskeptics.info/thread-1846.html

" They would know that the Stefan-Boltzmann equation applies to surfaces in a vacuum
without some mathematical assumptions and manipulations. "

Another excellent point. So, the question IS why is the earth's surface cooler than SB law says it should be, for a given solar input???
THERMODYNAMICS....AND NO DIVIDING P BY 4.
http://www.globalwarmingskeptics.info/thread-1324.html

[Richard111]

The internationally acclaimed Chemical Engineer Hoyt Hottel developed graphs and equations involving path length to heat transfer from and to combustion gases from actual measurements in the range 100F to 10,000F.

Love to see those graphs but would probably need a tutorial first.

Derek, your second point has also troubled me. The actual surface temperature is measurable. Then the air temperature directly above the surface is recorded at about 1.5 to 2 metres up and the temperature can be a couple of degrees or more LOWER than the surface temperature. This is far in excess of the usual dry air adiabatic lapse rate of roughly 1C per 100 metres. How come? I don't have anywhere near enough background education in this subject to try and work that out.

As cementafriend points out: "heat transfer... there are four types which affect surfaces a) conduction b) convection c) radiation and d) phase change".

That 'phase change' got me. But as I type I look out the window into the garden which has been well rained on lately and the soil is damp. Gotcha! Phase change! Now there is some surface cooling before the jolly old sun can start really warming things up. Anyone notice the current lack of sunspots? Solar cycle maximum and all that?

[Derek]

(06-22-2012 01:24 AM)Richard111 Wrote:  Derek, your second point has also troubled me. The actual surface temperature is measurable. Then the air temperature directly above the surface is recorded at about 1.5 to 2 metres up and the temperature can be a couple of degrees or more LOWER than the surface temperature. This is far in excess of the usual dry air adiabatic lapse rate of roughly 1C per 100 metres. How come? I don't have anywhere near enough background education in this subject to try and work that out.

Richard111, you will kick yourself... Yes, the surface temperature is measurable, and yes it is lower for a given IR input than the SB law indicates a black body would achieve.



Why? Thermodynamics, if you remember these illustrations I posted a while back.
We are not talking about a black body surface, we are considering what happens at a grey bodies surface....
Yes, it is complicated, but it is also quite simple really when you consider one item at a time.
(There are one or two I have unintentionally omitted from the following plots - I'll let you work them out for yourselves.
One obvious one to me - CLUE Eiffel tower....It's 6 inches taller in summer...)





Put another way.
Only part of the recieved IR at a surface will be lost in such a way as to warm the air that is measured a few feet above the ground. Most will be transferred in other ways, that may not directly heat the air, mostly change of state energy in the latent heat of water vapourisation.....
"phase change" is a term used to AVOID mentioning latent heat losses.....

The wet adibatic lapse rate is partly how much water vapour heats the surrounding air as well, which is something I am working on illustrating at present.....

[Richard111]

Thanks Derek. Still not clear to me yet. Will write an anecdote later to explain my thinking.

A couple of points; 'phase change' refers to a physical change of state of an element. When the discussion concerns 'climate' we know water is involved. Nothing is being hidden. It is the duty of the reader to make themselves familiar with the vocabulary of the subject or ask if unsure.
Next; I'm happy with the fact the Eiffel tower expands and contracts with changes in temperature but this does not enlighten me, especialy when there is only one of them.

Thank you for showing that black body thermal equlibrium graph. I've seen it before but it's nice to see it now in this discussion. I was using Wien's Law and the S-B equation to calculate temperature and radiative power at varius micron bands and find my figures follow the graph nicely.

But then that is for black bodies. What ever. I am personally convinced that 15 micron radiation from any source whatsoever cannot warm up a black or grey body above 194K (-79C) or thereabout. If the body in question warms above that temperature then there MUST be alternative heat energy input above and beyond what the 15 micron band can provide. It certainly won't be from 4.3 micron radiation because that implies a source at 673K (+400C) and same for 2.7 micron radiation which will be from a source at 1,073K (+800C). These temperature levels are simply not normal to the atmosphere. CO2 gas can only radiate at the temperature of the local air parcel which is mostly below 0C. The so called global average is maintained in the bottom 1.5 kilometres of the tropopause. The interesting thing from that graph is that the temperature range of -18C to +15C involves a radiative change of just over 100W/m^2. Not a lot really.

Now, to get back to the surface temperature and the rapid drop in temperature at the 1 metre to 1.5 metre level. I must say I am glad I breathe the air at my level and not at the level of the local moggies, mind you they do seem to sleep a lot. Yes, where was I? I was reading Willis E. over at WUWT the other day when he mentioned walking barefoot on beach sand in high summer. I've mentioned before that I have lived and worked in deserts. Walking around when air temperature is +40C or more is no real problem as long as you have a hat and something on your feet. I assume now the hat was to prevent your head getting as hot as the ground as there was no way white men could walk on the bare ground. Of course in those days we never bothered to record ground/surface temperature but we all knew not to put your hand on the car bonnet or what ever. Even picking up things from the ground was done cautiously. Another thing we noticed on hot days was willi-willies or dust devils. You could often see hundreds drifting along the ground in the almost still air. If I remember correctly, the stronger the breeze the larger, but fewer, the dust devels. The heat transfer mechanism in these dust devels must be impressive. I think there is something similar going on when you see the 'heat haze' wavering up from a hot tarmacadam road surface here in the UK on the occasional clear sunny summer day.

Consider now 1 square metre of ground. The first 2 cubic metres of air above the ground will mass at about 2,400 grams. The CO2 contained therein will mass at 1.4 grams. The water vapour content will be several grams, certainly more than double the CO2. To me this looks like very little heating capability but the I am not worried about heating, just why is the air temperature dropping by 2 or 3C in that first 2 metres?

Or is there a temperature drop? At the surface, air/solid interface, the air is absorbing heat energy by conduction and passing it up the column by conduction plus convection. The sun is shining and warming the surface. So in general it would seem however much surface warming from the sun is eventually ballanced by upwelling radiation PLUS conduction into the air. The first couple of centimetres of air will be almost the same as the surface but that heat energy is being dispersed up the column FASTER than the standard dry adiabatic lapse rate of about -1C per 100 metres.

After writing all this it appears to me that if a parcel of air aquires (for any reason) a temperature difference of more than say 2C over a vertical distance of half a metre or so it becomes 'swirly'. I guess something like this happens when dew point is reached and latent heat is released during the phase change from gas to liquid. Coupled to the local density drop due to coalsing water vapour molecules I guess it would get 'swirly' indeed. I can confirm from my PPL days that flying too near or just under clouds could give a very bumpy ride.

All very confusing I guess but that seems to be my normal state when attempting to understand 'climate change'.

[Derek]

Thank you for your original question Richard111, it has provided me with some insight.

Along the lines it has helped me with, and also to hopefully illustrate the surface to near surface air temperature drop you ask about, I think the following may help.

Steam, it is not liquid water nor gaseous water vapour. It is a sort of spray of liquid water, at the temperature of the body of water it came from. Steam, whether from a boiling kettle or the surface of a lake, stream, or river on a cold but sunny winters morning, is at that temperature. Hence the steam from a kettle will burn you, but the steam from a stream never could. But both just vanish into thin air...
Steam is little droplets of water, that heat the air, giving up some of the energy it carries. BUT, as steam vanishes it also takes energy it is carrying invisibly away as latent heat losses.
What determines this? The wet adiabatic lapse rate I assume. So, some energy contained in the moist air does not show in the air's temperature, because it is in latent heat form, as transported aloft by water vapour.
The energy contained within the air and the temperature of the air may well be two different things....

I think it might well be better to think in terms of energy density gradients rather than adiabatic cooling rates. Adiabatic cooling rates, both wet and dry are only PART of the picture.