variation in atmospheric pressure with altitude

[Bryce Ring]

I am having a hard time understanding the different Graph curves that are shown when Googling this title.

As far as I knew the pressure decreased more per gain x amount of altitude as you gain altitude, this made sence to me as there was less air in the lower pressure atmosphere to press down on you.

This is how I thought it worked.

http://www.ux1.eiu.edu/~cfjps/1400/atmos_struct.html

But wiki and some other sources say that the decrease in pressure is less per altitude gain per altitude gain such as.

is this just because it follows a constant 15c and 0%humididty ?

Help.

[Dodgey]

Well it isn't a linier progression. IIRC air pressure halves at 18000 feet but I can't remember when it halves again.

[K^2]

Pressure is equal to the weight of air above you (per unit of area). As pressure drops, so does density. As density decreases, the amount of air you leave bellow as you go up decreases as well. So pressure drops slower with altitude.

If you ignore temperature variations, in fact, pressure drops exponentially. This is the model that KSP uses, with P = P₀ exp(-h/H), where h is altitude above reference point, P₀ is pressure at that reference point, and H is scale height.

On a real planet with real atmosphere, temperature variations are significant, so the shape isn't quite exponential, but it can be reasonably approximated as such for some ranges of altitude.

[Nuke]

a more realistic model of earth's atmo is this:

[Bryce Ring]

So embarrassing, I had it backwards, now it TRULY makes sense, going to hide under a rock for a while.

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Nuke, that image is awesome.

[Nuke]

if you want to figure out pressure at an arbitrary altitude the math is here:

http://en.wikipedia.org/wiki/Density_of_air#Altitude

also the pic was from this article

http://en.wikipedia.org/wiki/International_Standard_Atmosphere