WW2010
University of Illinois

WW2010
 
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Online Guides
 
  introduction
 
> meteorology
 
  remote sensing
 
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  projects, activities

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

El Nino
 
  introduction
 
  definition
 
  '97-'98 event
 
  upwelling
 
  non el nino years
 
> el nino events
 
  sea surface temps
 
  impacts on weather
 
  economic impacts
 
  prediction

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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El Niño Events
results from weakening easterly trade winds

The easterly trade winds are driven by a surface pressure pattern of higher pressure in the eastern Pacific and lower pressure in the west. When this pressure gradient weakens, so do the trade winds. The weakened trade winds allow warmer water from the western Pacific to surge eastward, so the sea level flattens out.

[Image: animation of El Niño (77K)]

This leads to a build up of warm surface water and a sinking of the thermocline in the eastern Pacific. The deeper thermocline limits the amount of nutrient-rich deep water tapped by upwelling processes. These nutrients are vital for sustaining the large fish populations normally found in the region and any reduction in the supply of nutrients means a reduction in the fish population.

Convective clouds and heavy rains are fueled by increased buoyancy of the lower atmosphere resulting from heating by the warmer waters below. As the warmer water shifts eastward, so do the clouds and thunderstorms associated with it, resulting in dry conditions in Indonesia and Australia while more flood-like conditions exist in Peru and Ecuador.


[Image: legend explaining water temperature represented by colors in above diagram ]

El Niño causes all sorts of unusual weather, sometimes bringing rain to coastal deserts of South America which never see rain during non-El Niño years. The flooding results in swarming mosquitoes and the spread of disease.


[Image: legend explaining water temperature represented by colors in above diagram ]

The air-sea interaction that occur during an El Niño event feed off of each other. As the pressure falls in the east and rises in the west, the surface pressure gradient is reduced and the trade winds weaken. This allows more warm surface water to flow eastward, which brings with it more rain, which leads to a further decrease of pressure in the east because the latent heat of condensation warms the air...and the cycle continues.



non el nino years
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.

sea surface temps