# Barometric Pressure

posted by on .

Furthur to my recent question and thank you Bob.

Had the 32 feet being 33 feet I would have considered this close enough to 10m.

However I now understand there are many answers to the question of the decrease in barometric pressure with height all probably correct. Taking the mean barometric pressure at sea level and at the top of Everest I concluded that a decrease in the order of 85mb per Km was about right. Although I now realise it will not be correct to divide the difference in mb by the ht in Km to arrive at a decrease that will be correct at all altitudes under all circumstances.

The figure I found on the internet of 100 mb per Km may well be correct from sea level up to 1Km in ht but for a different altitude say between 9 Km and 10 Km a figure of 75 mb per Km might be more accurate. (or is it the other way round)

Anyone ant ideas?

Thank you,

Mike.

Since this is not my area of expertise, I searched Google under the key words "'barometric pressure' altitude" to get these possible sources:

http://www.sablesystems.com/baro-altitude.html
http://en.wikipedia.org/wiki/Atmospheric_pressure
http://www.usatoday.com/weather/wbarocx.htm
http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/barfor.html

I hope this helps. Thanks for asking.

The problem you are faceing is this:
Trying to reduce a complicated model of reality to a rule of thumb always leads to exceptions. No matter what rule you choose, (10km per 75mb), you will find it is only a guide.