Robert Soames Wetmore wrote: > > It was about 9 degrees Fahrenheit this morning and very clear out. It seems > it is usually or often clear when very cold. Dumb question but is this some > kind of rule: is it always/usually clearer when cold? And why? Is it > because of the cold, or some other related factor which may be present when > it is not cold or may sometimes not be present when it is cold)? Or is it > all in my imagination? Thanks and forgive my ignorance... > > Rob
How about this? With no cloud cover (nessary condition for MY explanation) all things exposed to the sky are exposed to something like 4 degrees Kelvin. Not far from absolute zero. Any heat in things on earth are radiating toward the much colder temperature of the sky. This is why tender exposed leaves on plants can freeze solid, when out door temps are recording 50 degrees, if there's no wind, and all the plant 'sees' is the clear night sky. That's why those tending the plants frequently cover the small plants with small tents on clear nights. To keep them from freezing! That's my contribution... keith whaley
