espere Environmental Science Published for Everyobody Round the Earth
Printer friendly version of this page
Home    Contact    Encyclopaedia    Mobility    International    PDF    magazine    - ? -   
Upper Atmosphere
basics
1. Understanding the stratosphere
- layers
- composition
- observation
* Worksheet 1
* Worksheet 2
2. Ozone hole
Ozzy Ozone
Links
PDF
more
     
 

Calculation of the relationship between atmospheric pressure and altitude for dry air

parameters and units:

z [m] = altitude

p0 [hPa] = pressure at the ground

p [hPa] = pressure at altitude z

R* = 287 J kg-1 K-1 = gas constant for dry air

R* = R / Ma

R = gas constant = 8.314 J K-1 mol-1

Ma = molecular weight of air = 28.96 g mol-1

 

basicsmore
basicsmore
basicsmore
basicsmore
basicsmore
basicsmore
basicsmore
basicsmore
 

g = gravity accelaration constand
= 9,81 m s-2

Tm [K] = mid temperature between the the temperature at the ground T0 and the temperature in altitude z Tz

Tm = (T0 + Tz) / 2

g / R* = 0,034 K m-1

 

1 J = 1 N m

1 N = 1 kg m s-2

 

pressure and altitude

pressure and temperature versus altitude

Relationship between pressure temperature and altitude. Full size: 90 K

The formula is only valid for dry air. For humid air the molecular weight changes.
For the plotted graph the following reasonable assumptions have been made:

Temperature at the ground: 20°C
Temperature decrease rate: - 1°C / 200 m
Temperature at 10000 m: - 30°C

Pressure at the ground: 1000 hPa

It can be seen from the calculated pressures in higher altitudes, that the pressure at 5,500 m is about 500 hPa, at 11,000 m it's about 250 hPa.

Click here to go back to the page on layers in the atmosphere.

 


About this page:
author: Elmar Uherek - MPI Mainz
last published: 2004-04-20

 

 top

ESPERE / ACCENT

last updated 21.02.2006 03:02:34 | © ESPERE-ENC 2003 - 2013