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*From*: Brian Whatcott <betwys1@sbcglobal.net>*Date*: Wed, 18 Jun 2008 11:42:17 -0500

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

plohstreter@mail.hockaday.org

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!

**Follow-Ups**:**Re: [Phys-l] Atmospheric pressure calculus deduction***From:*"Robert Cohen" <Robert.Cohen@po-box.esu.edu>

**References**:**[Phys-l] Atmospheric pressure calculus deduction***From:*"CARABAJAL PEREZ, MARCIAL ROBERTO" <MCARABAJALP@repsolypf.com>

**Re: [Phys-l] Atmospheric pressure calculus deduction***From:*"Pete Lohstreter" <plohstreter@MAIL.HOCKADAY.ORG>

**Re: [Phys-l] Atmospheric pressure calculus deduction***From:*Brian Whatcott <betwys1@sbcglobal.net>

**Re: [Phys-l] Atmospheric pressure calculus deduction***From:*"Pete Lohstreter" <plohstreter@MAIL.HOCKADAY.ORG>

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