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PHOTO CAPTION                      P-49158
                                   September 15, 1997
                                   TOPEX/El Nino confirmation

These four views of the Pacific Ocean were produced using sea 
surface height measurements taken by the U.S./French 
TOPEX/POSEIDON satellite. The images show sea surface height 
relative to normal ocean conditions from March 1997 through June 
1997. This evolutionary view is providing oceanographers with  
more convincing information that the weather-disrupting 
phenomenon known as El Nino is back and getting stronger. The 
white and red areas indicate unusual patterns of heat storage; in 
the white areas, the sea surface is between 14 and 32 centimeters 
(6 to 13 inches) above normal; in the red areas, itís about 10 
centimeters (4 inches) above normal. The surface area covered by 
the warm water mass is about one and one-half times the size of 
the continental United States. The added amount of oceanic warm 
water near the Americas, with a temperature between 21-30 degrees 
Celsius (70-85 degrees Fahrenheit), is about 30 times the volume 
of water in all the U.S. Great Lakes combined.  The green areas 
indicate normal conditions, while purple (the western Pacific) 
means at least  18 centimeters (7 inches) below normal sea level.  
The El Nino phenomenon is thought to be triggered when the steady 
westward blowing trade winds weaken and even reverse direction.  
This change in the winds allows a large mass of warm water (the 
red and white area) that is normally located near Australia to 
move eastward along the equator until it reaches the coast of 
South America. The displacement of so much warm water affects 
evaporation, where rain clouds form and, consequently, alters the 
typical atmospheric jet stream patterns around the world. Using 
these global data, limited regional measurements from buoys and 
ships, and a forecasting model of the ocean-atmosphere system, 
the National Centers for Environmental Prediction (NCEP) of the 
National Oceanic and Atmospheric Administration, (NOAA), has 
issued an advisory indicating the presence of the early 
indications of El Nino conditions. 

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