sci.energy

On Mon, 13 Aug 2007 22:30:44 -0700, Whata Fool wrote:

> On Mon, 13 Aug 2007 15:53:26 -0700, Bill Ward
> wrote:
>
>>I think that question is still up for grabs. There's no doubt it all
>>must be radiated, but from exactly which levels and by what seems
>>obscure.
>
> Doesn't the temperature gradient with altitude show that?

In the troposphere, it's basically the adiabatic lapse rate - what you get
if you expand a gas without transferring any energy in or out. It's also
modified by the convection, humidity, and latent heat effects. In stable
atmospheric conditions, if you lift a parcel of air to a new altitude, it
either stays there or sinks. In unstable conditions, a lifted parcel of
air will continue to rise. The actual radiation profile will be quite
complex, depending on WV and cloud/haze formation. In hot weather, I
think the trip up is fast enough to that most radiation comes from
the cloud tops. Satellites should be able to check that, as the IR
wavelength depends on altitude.

>
>>What would be the effect? It seems to me space should just look like a
>>3K black body. What am I missing?
>
> The atmosphere? Radiation flux of anything below room
> temperature has to be fairly low. If the outgoing radiation of an
> object (ignore the incoming for this) is related to the temperature, it
> must be related to the relative velocity of the molecules and in some
> way to the mean free path.
>
> This is where there is a lot of science assumed simply on the
> basis of the writings from the 1800s.
>
> It isn't clear that those authors of the 1800s papers knew
> that temperature decreases with altitude in a very regular way (ignoring
> the relatively rare occurrence of temperature inversion).
> And it isn't clear if those authors from the 1800s knew the
> temperature depends on the velocity of molecules or any relation to the
> mean free path.
>
> It is almost certain (in my opinion) they did not know that
> the speed of sound in a specified gas is almost totally dependent on
> temperature, because sound cannot be transferred from molecule to
> molecule faster than the molecules travel. Since the atmosphere is
> air (with trace gases), pressure pretty much falls out of the equation
> to calculate the speed of sound (all air is pretty much the same).
> It is not unusual to find an expert aerospace scientist that
> doesn't know the speed of sound in the atmosphere is dependent mostly on
> temperature.
>
> With the lower temperatures at altitude, the radiation must
> also depend to some extent on altitude, but the longer mean free paths
> at altitude may allow IR radiation to proceed easier.
> While the surface of the Earth may radiate at many or any IR
> frequency, the atmosphere must radiate at specific frequencies, but with
> greater altitude, the longer mean free path must enhance the outward
> radiation away from purely omnidirectional.
>
> And a good mathematical description of the radiation
> complex should show that outward radiation dominates for both the
> reasons of higher temperature at low altitude and because of the longer
> mean free path at higher altitudes, plus the mathematical summation of
> the spherical Earth.
>
> An important point possibly overlooked is the fact that in
> the atmosphere, a maximum high arises regardless of the amount of
> sunlight and the clearness of the atmosphere.
> That means radiation and convection increase more rapidly
> with only slightly higher temperatures.
> The record maximum of about 134 F in dry desert areas gives
> a good indication of the possible radiation and convection mechanisms,
> apparently without any of the effects of evaporative cooling by water
> vapor.
>
> How long will the gossip fad go on before papers specific
> to IR radiation by the surface, the atmosphere and the various trace
> gases reveal exactly what the effect of CO2 is.
>
> I can only guess about two more years, depending on how the
> 2008 US election goes.