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El Niño still lingering in Pacific
May 12, 1998
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 May 3, 1998, and sea-surface height is an
indicator of the heat content of the ocean. The image shows that
sea-surface height along the central and eastern equatorial
Pacific has maintained a near normal state since March 1998.
However, the western equatorial Pacific, shown here in purple,
has not returned to a normal state and is still about 30
centimeters (12 inches) below normal sea level. Remnants of the
El Niño warm water pool, shown in red and white, are situated to
the north of the equator. Oceanographers indicate these
measurements show that the Pacific has not yet fully recovered
from this large El Niño event. These sea-surface height
measurements have provided scientists with a detailed view of how
the 1997-98 El Niño's warm water 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. 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 satellite imagery, buoy and ship data,
and a forecasting model of the ocean-atmosphere system, the
National Oceanic and Atmospheric Administration, (NOAA), has
continued to issue an advisory indicating the so-called El Niño
weather conditions that have impacted much of the United States
and the world are expected to remain through the spring.
For more information, please visit the TOPEX/Poseidon project
web page at
http://topex-www.jpl.nasa.gov/
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