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From: den@parallel.UUCP (Dennis Briscoe)
Newsgroups: net.sci
Subject: Wind Chill Factor?
Message-ID: <244@parallel.UUCP>
Date: Thu, 2-Aug-84 15:43:58 EDT
Article-I.D.: parallel.244
Posted: Thu Aug  2 15:43:58 1984
Date-Received: Sun, 5-Aug-84 05:27:29 EDT
Lines: 35

Can anyone tell me how wind chill factors are  calculated?   I  often  hear
television  and  radio  announcers  talk about how cold it is at a football
game, etc. "The temperature is 12 degrees fahrenheit with  the  wind  chill
factor making it -20 degrees."

With just a little thought one realizes that it isn't likely that air at 12
degrees  could cool an object down to -20 degrees.  It won't likely cause a
pond to freeze, for instance.  There could be some cooling  due  to  faster
evaporation,  but is the wind chill factor dependent on the humidity of the
air and the surface moisture of the object in question?

When I discussed this question with another person at work some  time  ago,
he  said that since the body warms the air around it, thermal layers of air
form.  These layers are stripped off by the wind.   This  makes  a  lot  of
sense  to me, but it still means that the wind chill factor is dependent on
the amount of heat transferred from the body (or from any object whose tem-
perature is higher than ambient).  The internal temperature and the type of
insulation on a person or other object would make a big difference.  In the
"12 degrees / -20 degrees" example, if a block of ice were on the field, it
would melt faster than it would with no wind at 12 degrees, and  of  course
at -20 degrees it wouldn't melt at all.

Perhaps wind chill factor is only supposed to  be  a  rough  guideline  for
adjusting  calculations for probable survival time in the wilderness.  Many
of the questions still apply, and as I have mentioned, it is often used  in
other contexts.

So, my questions are, "How is wind chill factor calculated?", "Is it scien-
tifically  valid?",  "Does it apply only to humans?", and "What assumptions
are made about clothing, etc.?"

				Einstein didn't know beans,
				(but that's another story)

				Dennis Briscoe - - Parallel Computers