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Quoting Bernard Cleyet <anngeorg@PACBELL.NET>:this implies thermal inertia. theoretically, check from the SH of dry
I suppose this radiance is due to absorption from the earth's
radiation. It approximates a black body at 300 deg. K
This supposition bespeaks a physical model that I don't
understand. At the very least, there is an alternative model
that ought to be considered, to wit:
The atmosphere radiates 'because' it has a temperature. It has
a temperature 'because' of a number of inputs, including
-- direct heating by solar radiation
-- latent heat liberated by moisture when it condenses in theThe amount of moisture can be determined (remote sensing) and therefore,
atmosphere
-- heat transferred by contact with the surfaceif the air is still, I don't think significant. The data's graph I
-- etc. etc. etc.
Levi reports the atmosphere's spectral radiance as ~ > 0.8 W / m^2 - sr
- micron from 5 micron => > 20. (any angle)
I really doubt Levi is telling the whole story. My friends who own
big IR telescopes tell me the contribution they receive from the
atmosphere depends on the _water column_ they have to look througth,
and not much else. If the air is dry, they can more-or-less see
right through it. So it's good to have a site with high altitude
and/or dry weather.
Reminds me of Arabs who made ice in the desert using blankets
(ca. 500 CE ?) reported by G. Gamow.
I've repeated the experiment myself, making ice in the desert
using styrofoam coolers et cetera. Works fine. Impresses the
tourists.