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"Perhaps someone would care to try it?"
Not really.
...
Levi reports the atmosphere's spectral radiance as ~ > 0.8 W / m^2 - sr
- micron from 5 micron => > 20. (any angle)
From ~ 0 to 2 deg. it rises to ~ 10 X ( 8 W ...) between 7 and 14
micron *. by 20 micron it is ~ 3 W / m^2 etc. measured at ~ 3 km, 8
deg. C, and clear night. I assume no moon
...
I suppose this radiance is due to absorption from the earth's
radiation. It approximates a black body at 300 deg. K Would be
interesting to see how it changes with time.
bc
Brian Whatcott wrote:
>At 01:04 PM 3/13/2004, John M., you wrote:
>
>
>>>When dew forms on clear nights, it will heavily wet lawns but will
>>>hardly ever leave visible moisture on concrete walkways or asphalt
>>>roads. There are many factors that regulate condensation:
>>>temperature, available condensation nucleii, curvature, hydrophilic
>>>surfaces, etc. - but I am having difficulty identifying the primary
>>>one in this case. Any ideas out there?
>>>
>>>
>>The primary mechanism is radiation exchange with 2 pi steradians of a
>>3 kelvin blackbody plus high resistance thermal conduction pathways
>>to the ground and the (still) air.
>>
>>--
>>John Mallinckrodt mailto:ajm@csupomona.edu
>>
>>
>
>If we are to believe John, a vacuum enclosure with a suitably
>transparent lid would allow a black chromed copper square (say),
>if well insulated at sea-level, to cool to 5 or 6 K overnight?
>I don't think so.
>I think you would find it rather difficult to radiatively
>chill any object at sea level to below -100 degC
>
>Perhaps someone would care to try it?
>
>Brian Whatcott Altus OK Eureka!
>
>
>