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elnino2.txt
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1995-02-23
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PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
PHOTO CAPTION P-45140
January 24, 1995
These three panels show the evolution of sea surface elevation
over the global oceans from October to December 1994. The
red-colored strips in the central and eastern tropical Pacific
reflect the formation of the present El Nino condition. The
images were created with the sea surface elevation data taken by
the radar altimeter onboard the TOPEX/Poseidon satellite. The
color coded maps show monthly sea surface elevation relative to
the two-year average taken during 1993-94. Higher sea surface
elevation is shown in red and yellow while lower elevation
is in purple and blue. The higher sea surface elevation
associated with the El Nino reflects an excessive amount of
unusually warm water in the upper ocean. El Nino begins when a
phenomenon called a Kelvin wave is created in the western
tropical Pacific when the trade winds weaken. The Kelvin wave
subsequently travels eastward along the equator carrying with it
an unusually warm water mass under a bulge of high sea surface
elevation. These maps show a new Kelvin wave arriving at the
western coast of South America in November 1994. In December,
scientists believe the trailing part of the wave was somehow
reinforced, causing the wave to stagnate in its present location.
The red and white feature shown in the Indian Ocean is caused by
seasonal monsoon winds. TOPEX/Poseidon is a joint program of
NASA and the Centre Nationale d'Etudes Spatiales, the French
space agency. Scientists use the TOPEX/Poseidon sea surface
elevation data to produce global maps of ocean circulation.
Launched Aug. 10, 1992, the satellite has completed two and a
half years of its three-year prime mission and has provided
oceanographers with unprecedented global sea surface elevation
that is accurate to better than 5 centimeters (2 inches). The
Jet Propulsion Laboratory manages the TOPEX/Poseidon satellite
for NASA's Office of Mission to Planet Earth.
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