Ask A Scientist© Weather Archive

name       Mike
status     other
age        40s

Question - Assuming standard day conditions, what is the air pressure at 6200
feet in psi? If I remember my high school physics it is 14.7 psi at
sea level. Are there tables or charts that show the relationship of
air pressure to altitude factoring in variables such as temperature and 
relative humidity?

Mike -

Let me answer part of your question.

If you use inches of mercury (29.92 in hg is standard) you can subtract one
inch of mercury for each thousand feet up to about 18,000 feet and be fairly
accurate. For your 6200 feet this would be 6.2 in hg less... 23.72 in hg. If
you wanted to make it PSI you could set up the ratio and convert it. Hope
this helps.

Larry Krengel
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Mike,

PSI units are not ordinarily used for
atmospheric pressure, mb (millibars) are.
Sea level pressure is approximately 1013 mb,
or 14.7 PSI (as you said).  Atmospheric
pressure in the lower part of the atmosphere
drops approximately 10 mb in 100 meters.  For
6200 feet (1889.8 meters) the pressure drops to
824 mb, or 11.95 PSI.  This is an approximation
of course, as various weather patterns and
conditions can cause it to be somewhat different.


David R. Cook
Atmospheric Section
Environmental Research Division
Argonne National Laboratory
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