Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: Dew Formation



I think BC and I have different unstated assumptions.

I can follow what BC is saying if (and, so far, only if) I
assume he is using a model that treats the sky as a non-
dissipative scatterer. Physically, that corresponds to
treating the scattering process as an undamped oscillator.
This is not an intrinsically absurd model ... just last
evening I saw a beautiful sunset with clouds that looked
red. In such a model Floquet's theorem applies; if the
incident beam has frequency omega the scattered beam has
the same frequency.

However, I thought we were discussing dew formation on
basically *clear* nights. Under such conditions, I think
a distinctly different set of assumptions applies, namely:
The scatterers are definitely *damped* oscillators. Floquet's
theorem does not apply ... you send in whatever incident
beam *you* like, and the sky emits whatever *it* likes,
according to its temperature and emissivity.

-- direct heating by solar radiation

this implies thermal inertia.

Yes indeed, I believe the air has thermal inertia. Small
volumes don't have a lot of inertia, but multi-mile-thick
layers do.


-- latent heat liberated by moisture when it condenses in the
atmosphere
... This would tend
to make the atmosphere temporally isothermal.

Actually, the opposite is true. Condensation tends to create
local hot spots leading to convection that stirs the atmosphere,
re-establishing the usual near-adiabatic profile. The height
of the troposphere is, not coincidentally, comparable to the
height of the tallest thunderstorms.