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# Re: [Phys-l] Atmospheric pressure calculus deduction

At 09:15 AM 6/18/2008 (??) , I wrote:

Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu> writes:
>This looks like a physicist's atmosphere to me.
>Temperature plays a role in determining seal level pressure.
>All the way up!

Actually, a pilots atmosphere. This is how airlines and private pilots
determine the quality of the atmosphere for safe flight.

Yes, temperature is a factor. The equation assumes a standard lapse rate.

Pete Lohstreter "Happy is he who gets to know
The Hockaday School the reasons for things. "
11600 Welch Rd Virgil (70-19 BCE) Roman poet.
Dallas, TX 75229

214-360-6389

My hasty response from lunchtime yesterday might have been
calculated to provoke a reply of this kind.
Let's see if I can address Roberto's question repeated below
in a less inflammatory way - though time is still short...]

************************
Hello:

I would like to show how atmospheric pressure at sea level can be
computed from the weight of a column air above us, considering earth
mass, dimensions, and gravity but I could not find a proper model that
also describe altitude efects . Do you know about such model , or can
give me any guidelines ?. Thanks.

Roberto
***********************

An exact analytical answer to Roberto's question is essentially impossible.
The weight of a column of air at a given ground position to near-space
would need certain data on the density of the column at all points.
This depends on temperature, wind, air composition and so on.
Moist air is less dense than dry air, and warm air is less dense
than cool air.

Estimates using assumptions about atmospheric composition and
temperature gradient can be generated which exclude practical
effects like thermal inversions, increasing temperatures at
great heights, the presence of moist less dense air masses,
o and winds aloft.

What is most useful for pilots is a measure of altitude
that can provide some assurance of height above ground at an
intended landing point, and some assurance that other pilots flying
at directed separations in altitude never come close to colliding.
This is the motivation for an 'artificial 'atmosphere specified by
ICAO relating pressure and altitude, which altimeters are now designed
to indicate, given that a setting for the hypothetical sea level pressure
can be inserted in the altimeter for that location.

Brian Whatcott Altus OK Eureka!