User:Geek.not.nerd

Variation in atmospheric pressure with altitude, computed for 15^oC and 0% relative humidity.

Pressure varies smoothly from the Earth's surface to the top of the mesosphere. Although the pressure changes with the weather, NASA has averaged the conditions for all parts of the earth year-round. As altitude increases, atmospheric pressure decreases. One can calculate the atmospheric pressure at a given altitude. Temperature and humidity also affect the atmospheric pressure, and it is necessary to know these to compute an accurate figure. The graph at right was developed for a temperature of 15^oC and a relative humidity of 0%.

This plastic bottle was sealed at approximately 14,000 feet altitude, and was crushed by the increase in atmospheric pressure (at 9,000 feet and 1,000 feet) as it was brought down towards sea level.

The equation relating atmospheric pressure p in kPa to altitude h in meters and other parameters is

$p=p_{0}\cdot \left(1-{\frac {L\cdot h}{T_{0}}}\right)^{\frac {g\cdot M}{R\cdot L}},$

where the constant parameters are as described below:

Parameter	Description	Value
P0	sea level standard atmospheric pressure	101325 Pa
L	temperature lapse rate	0.0065 K/m
T0	sea level standard temperature	288.15oC
g	Earth-surface gravitational acceleration	9.80665 m/s2
M	molar mass of dry air	0.0289644 kg/mol
R	universal gas constant	8.31447 J/(mol•K)

External Links

Air Pressure vs. Altitude YouTube video from the Naval Aviation Museum accessed 05032011

Air Pressure at Altitude calculator at altitude.org This site also contains information about altitude sickness and the effects of altitude on oxygen in the blood.