2010/04/07

SW LW radiation in oceans

Harry Lu (20:11:48) :

” George E. Smith (18:08:33) :
Bob you are so charitable. LWIR warms the top few cm. I figure that atmospheric (tropospheric anyway) LWIR can hardly be significant below about 3-4 microns…; so lets be generous and say it might warm the top 10 microns. How much of that energy remains following the prompt evaporation from that hot skin.”

Have you not forgotten conduction? It operates in all directions!

So we have the top few cm heated by sw and lw and a few 10s meters down heated by UV
http://ies.jrc.ec.europa.eu/uploads/fileadmin/Documentation/Reports/Global_Vegetation_Monitoring/EUR_2006-2007/EUR_22217_EN.pdf

So the surface cm is absorbing a percentage of the SW (as does each cm of the deeper water except the percentage is of a progressively smaller maximum) plus all the LW re-radiated from GHGs.

The surface is also receiving LW from the layer under the surface and radiating LW down to this lower layer. Because the surface is hotter this will average out to an energy transfer downwards.

So the hotter the surface the less the lower water energy will be radiated (lost) into the atmosphere. Less loss with the same SW TSI heating the lower layers will mean a hotter temperature.

Of course the surface is loosing heat via conduction in all directions radiation in all direction, and forced air convection upwards (sideways!)

However, The surface layer heating must effect the lower layer cooling in my books.

According to your diagram of energy buget:
http://wattsupwiththat.files.wordpress.com/2010/03/trenberth_mine_latest_big1.jpg

Only 169 w/m^2 of SW radiation gets absorbed (198w/m^2 hits the ground)
The back radiation from GHGs is 321 w/m^2 absorbed by the ground.

If 321W/m^2 is absorbed in the top layer and 169w/m^2 is absorbed in 10s meters the the top layer will be much warmer than the lower layers.

So is it not true that this top layer must control the temperature of the lower layers?

“”" Harry Lu (20:11:48) :

” George E. Smith (18:08:33) :
Bob you are so charitable. LWIR warms the top few cm. I figure that atmospheric (tropospheric anyway) LWIR can hardly be significant below about 3-4 microns…; so lets be generous and say it might warm the top 10 microns. How much of that energy remains following the prompt evaporation from that hot skin.”

Have you not forgotten conduction? It operates in all directions! “”"

Haven’t forgotten a thing Larry; you obviously didn’t read my post very closely; or alternatively I didn’t write it very well.

My post dealt with one very simple 8th grade high school science concept.

# 1 the incidence of solar spectrum radiation (UV to IR) on the deep ocean surface; at approximately 1000 W/m^2 max (sun directly overhead no clouds).

#2 the incidence of LWIR thermal radiation from the atmosphere (or from cloud reflections) in the range of perhaps 6-100 micorns on that same ocean surface at 324 W/m^2 according to Trenberth.

That is ALL that my post was about; those two electromagnetic radiation sorces of energy; both of which are treated by “climatologists” as “forcings”; so many Watts per square metre. As if somehow they are the same thing and produce the same results given their relative surface irradiances.

Of course they are NOT the same thing because of the things I clealy stated in my original post.

Nothing in my post suggested that there were NO OTHER physical processes of any kind going on as well; so my post contained nothing about quantum chromodynamics, or starlight, or backside thermal radiation from the moon, or anything else.

If you wish to contribute something about conduction (why didn’t you include convection) to the discussion; please do so; but don’t go thinking that I didn’t include that in my post because I forgot about it.

Obviously you didn’t understand the nature of the difference between solar spectrum radiation and its water absorption curve, and LWIR thermal radiation and its very differnet water absorption curve. That alone is what my post was about; not a complete treatise on global thermal physics.

Harry Lu (13:14:53)
Mr E. Smith, why so angry!?
your comment said:
” so lets be generous and say it might warm the top 10 microns. ”

I simply suggested that this would also propagate downwards by conduction and would not remain at 10um – and I don’t thinc convection works upside down at temps above 0C approx.?

I then suggested that if there was a hot water layer (even very thin) it would enable the underlying thermal structure heated by SW radiation to heat more since the energy loss is effectively stopped. energy radiated down into layer 10um below 10um surface hot layer is greater than the energy transported from the lower lay to the upper. i.e. there is a net flow downwards.

The fact is the sw radiation looses energy to the water at reducing amounts from the surface down. Each molecular layer absorbs some (say A%*169) energy and the rest passes through to the next layer (169-A%*169). This layer absorbs A% of what it receives (169-A%*169)*A% etc The surface layer therefore absobes most LW and a bigger quantity of the SW than subsequent “layers”. As you say it will be much hotter than layers below without any mixing or conduction.

This must stop the lower layers losing heat??

If you can convince me otherwise I am willing to listen.

Harry Lu (15:01:02)
“anna v (21:31:50) :
Re: Harry Lu (Apr 7 13:14),
The inside layers of the water, supposing there is no convection, will lose heat by conduction only. … LW in water can travel less than a micron before being absorbed, so it cannot get out as long wave except from the few microns of the surface. It will reach the surface through conduction.”

If I am understanding you, then 1um below the surface will not radiate to the air but heat will conduct to the surface and then radiate/conduct/evaporate to the air.

This is the same as I understand it.

but I also assume that radiation will go in all directions from each heated molecule. Some will heat the 1um towards surface. some will heat the next 1um down the 1um down will also radiate in all directions but will be at a lower temperature. Hence there will be less radiation to surface than the surface radiates down.
There will be a net frow of energy from surface downwards by radiation.
The conduction I assume is also equal to all connecting molecules so conduction from the surface hot molecules will conduct to the lower cooler molecules and the cooler molecules will conduct to the hot molecules but at a lesser rate.
Hence there will be a net flow of energy downwards.
Convection will cause energy to flow in the direction of the molecular gross movement. At normal (non freezing) sea temperatures the surface will be made up of less dense warm water and the lower layers will be more dense cold water
Hence convection will not occur? there will be mixing by molecular motion but again this will favor heating the cool layers.

TSI SW will penetrate the depths warming them but as I pointed out 198W hits the surface, less hits each succeeding molecule as it passes downward therefore more energy will be absorbed by the surface layers (assuming homogeneous water absorption). the surface 1um will also receive the back radiation (LW) 321W.

As far as I can see the hot layer will control the loss of energy from the depths. Hot surface = hotter depths

/harry

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