WW2010
University of Illinois

WW2010
 
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Online Guides
 
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> meteorology
 
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Meteorology
 
  introduction
 
  air masses, fronts
 
  clouds, precipitation
 
  el nino
 
  forces, winds
 
  hurricanes
 
  hydrologic cycle
 
  light, optics
 
> midlatitude cyclones
 
  severe storms
 
  weather forecasting

Midlatitude Cyclones
 
  introduction
 
  definition
 
  associated winds
 
  air masses
 
  on satellite images
 
> upper air features

Upper Air Features
 
  geopotential height
 
  troughs
 
  ridges
 
  wave amplification
 
  rising motion
 
  steering level
 
  jet stream
 
  jet streaks
 
> vertical motions
 
  mid-level moisture
 
  wind vectors

User Interface
 
  graphics
> text

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Vertical Motion and Jet Streaks
associated with different regions of a jet streak

Jet streaks are important as they are indicative of rising motion/falling pressures at the surface. The figure below represents an idealized jet streak.

As air enters from the left, it must be accelerated. The force to do this is supplied by the Coriolis force as air flows from the south to the north near the jet entrance, leading to a force to the east (the right). This air motion results in a convergence to the north and a divergence to the south. As a result, air sinks in the northern 'quadrant', and rises in the southern quadrant, leading to pressure changes at the surface. In the jet exit region, the opposite happens, as air flows from north to south to create the force necessary to decelerate the air as it leave the jet streak. The vertical motion resulting from this leads to rising air in the north quadrant and sinking air in the south, also leading to surface pressure changes. Look at this 300mb map for 12Z, April 6,1997.

[Image: (45K)]

Notice the jet streak that lies along the southeastern U.S. Now look at the following surface pressure plots.

[Image: (56K)]

[Image: (51K)]

Notice how pressures have risen below the north entrance region, and fallen below the north exit region. This will intensify cyclones which tend to be located below the north exit quadrant.



jet streaks
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.

mid-level moisture