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New Satellite image captures 1997 El Niño rhythm
December 18, 1997
This image of the Pacific Ocean was produced using sea surface
height measurements taken by the U.S.-French TOPEX/Poseidon
satellite. The image shows sea surface height relative to normal
ocean conditions on Dec.10, 1997 and sea surface height is an
indicator of the heat content of the ocean. The volume and area
of the warm water pool related to El Niño has increased again
after reaching a temporary low around Dec. 1. TOPEX/Poseidon
has been tracking the fluctuations of the El Niño warm pool since
it began early this year. Oceanographers believe the recent
increases and decreases in the size of the warm water pool at the
equator are part of the natural rhythm of El Niño and that the
warm pool is occasionally pumped up by wind bursts blowing from
the western and central Pacific Ocean. Each wind burst has
triggered a temporary increase in area and volume of the warm
pool. These data collected throughout 1997 have provided
scientists with their first detailed view of how El Niño's warm
pool behaves because the TOPEX/Poseidon satellite measures the
changing sea surface height with unprecedented precision. In this
image, 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, it's
about 10 centimeters (4 inches) above normal. The green areas
indicate normal conditions, while purple (the western Pacific)
means at least 18 centimeters (7 inches) below normal sea level.
The El Niño 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 a strong El Niño
condition throughout the winter.
For more information, please visit the TOPEX/Poseidon project
web page at
http://topex-www.jpl.nasa.gov/
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