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JET PROPULSION LABORATORY
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PHOTO CAPTION                           P-46847
                                        April 12, 1996
                                        Rossby Waves
                                        TOPEX/Poseidon

This image shows three scenes taken from an animation created by 
TOPEX/Poseidon data of the ocean. The scenes show large-scale 
ocean waves with wavelengths of hundreds of kilometers, called 
Rossby waves.  These waves carry a "memory" of  weather changes 
that have happened at distant locations over the ocean. 
Scientists at Oregon State University are using the satellite 
data to track these waves as they move through the open ocean and 
have determined that at mid-latitudes the Rossby waves are moving 
two to three times faster than the existing theory predicts. 
Because Rossby waves can alter currents and their corresponding 
sea surface temperatures, the waves influence the way the oceans 
release heat to the atmosphere and, thus, are able to affect 
weather patterns. Precise information about how fast the waves 
travel may help forecasters improve their ability to predict the 
effects of El Nino events on weather patterns years in advance.  
The colors show variations in sea level in the Pacific Ocean.  
White and red indicate higher than average levels, while purple 
and magenta show lower than average levels.  These scenes were 
taken by TOPEX/Poseidon in April, July and December 1993.  The 
two small black circles in the April image show an area of warm 
water, called a Kelvin wave, moving along the equator toward the 
coast of the Americas.  When this area of high sea level meets 
the coast, it creates two coastal waves, one traveling northward 
and the other traveling southward along the American coast.  As 
these waves move poleward, Rossby waves "peel off" the coast and 
travel west.  The solid lines show the crests of the waves (high 
sea level), while the dashed lines show wave troughs. 
TOPEX/Poseidon, a joint program of NASA and the Centre Nationale 
d'Etudes Spatiales, the French space agency, uses a radar 
altimeter to precisely measure sea-surface height. The Jet 
Propulsion Laboratory manages the U.S. portion of the 
TOPEX/Poseidon mission for NASA's Office of Mission to Planet 
Earth.

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