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

Clouds, Precipitation
 
  introduction
 
> development
 
  cloud types
 
  precipitation

Development
 
  states of water
 
  relative humidity
 
> rising air
 
  convection
 
  convergence
 
  topography
 
  fronts
 
  rain or snow

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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Rising Air
a key process in the production of clouds and precipitation

Imagine a block of air, or air parcel, rising upward through the atmosphere. The air parcel expands as it rises and this expansion, or work, causes the temperature of the air parcel to decrease.

As the parcel rises, its humidity increases until it reaches 100%. When this occurs, cloud droplets begin forming as the excess water vapor condenses on the largest aerosol particles. Above this point the cloud droplets grow by condensation in the rising air.

If the cloud is sufficiently deep or long lived, precipitation will develop.

The upward motions that generate clouds and lead to precipitation can be produced by convection in unstable air, convergence of air near cloud base, lifting of air by fronts and lifting over elevated topography such as mountains.



relative humidity
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.

convection