WW2010
University of Illinois

WW2010
 
  welcome
 
> online guides
 
  archives
 
  educational cd-rom
 
  current weather
 
  about ww2010
 
  index

Online Guides
 
  introduction
 
> meteorology
 
  remote sensing
 
  reading maps
 
  projects, activities

Meteorology
 
  introduction
 
  air masses, fronts
 
  clouds, precipitation
 
  el nino
 
> forces, winds
 
  hurricanes
 
  hydrologic cycle
 
  light, optics
 
  midlatitude cyclones
 
  severe storms
 
  weather forecasting

Forces, Winds
 
  introduction
 
> pressure
 
  pressure gradient
 
  coriolis force
 
  geostrophic wind
 
  gradient wind
 
  friction
 
  boundary layer wind
 
  sea breezes
 
  land breezes

Pressure
 
  definition
 
> variation with height
 
  isobars
 
  pressure surfaces
 
  variation with temps
 
  high pressure center
 
  low pressure center

User Interface
 
  graphics
> text

NOTE: We've guessed that you're not using a client that supports colored tables and have tried to compensate. Low graphics mode looks much better on clients that do... we recommend switching to Netscape 3.0 or Microsoft Internet Explorer.
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Pressure with Height
pressure decreases with increasing altitude

The number of air molecules above a surface changes as the height of the surface above the ground changes. For example, there are fewer air molecules above the 50 kilometer (km) surface than are found above the 12 km surface. Since the number of air molecules above a surface decreases with height, pressure likewise decreases with height.

Most of the atmosphere's molecules are held close to the earth's surface by gravity. Because of this, air pressure decreases rapidly at first, then more slowly at higher levels.

Since more than half of the atmosphere's molecules are located below an altitude of 5.5 km, atmospheric pressure decreases roughly 50% (to around 500 mb) within the lowest 5.5 km. Above 5.5 km, the pressure continues to decrease, but at an increasingly slower rate (to about 1 mb at 50 km).



definition
Terms for using data resources. CD-ROM available.
Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.

isobars