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RE: The last good day?

Subject: RE: The last good day?
From: Chuck Renner <>
Date: Tue, 12 Nov 2002 12:19:38 -0600
> Some times, if there are no clouds, cold objects will actually
> radiate enough heat into the atmosphere to lower their temperature
> below that of the surrounding air.  That's why you can have frost
> on a windshield when there's no frost on the ground.  Seems
> counterintuitive, but I've heard it on good authority.  Something
> to do with radiant versus conductive versus convective heat exchange.
> Maybe someone more versed in thermodynamics can explain it better.

Thankfully, never had to take thermo, so I can't say whether this concept is
correct or not.

However, frost on the windscreen with no frost on the ground is very easy to
explain.  The ground has a much greater thermal mass than the air, so it
takes a long time to cool sufficiently for frost to form.  Your windscreen
on the other hand doesn't have much thermal mass, and is sitting out in the
cold air, so it gets cold pretty quickly.

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