MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
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Contact: Mary Hardin (818) 354-0344
FOR IMMEDIATE RELEASEJune 2, 1998
NASA SATELLITE DATA REVEAL NEW CLUES ABOUT EL NIÑOíS INFLUENCE ON
U.S COASTAL WATERS
In-depth study of satellite data obtained at the onset of
the 1997-98 El Niño event has given scientists more conclusive
evidence that the unusual warming of waters along the equator and
the west coast of the U.S. was linked to changes in wind patterns
in the Pacific ocean.
Using measurements taken by the NASA Scatterometer (NSCAT)
in early 1997, scientists confirmed that an unusual weakening of
the trade winds preceded an increase in sea surface temperatures
along the central and eastern equatorial Pacific, according to
Dr. W. Timothy Liu, the NSCAT project scientist at JPL. "With
NSCAT we are able to see the whole El Niño picture, and we now
know that the unusually high ocean temperatures at the equator,
along the North American coast and off of Baja, Mexico are all
linked together because of the winds," Liu said.
Liu is presented his findings last week at the American
Meteorological Societyís Conference on Satellite Meteorology and
Oceanography in Paris.
An El Niño condition is thought to be triggered when steady
westward blowing trade winds weaken and even reverse direction.
This change in the winds allows the large mass of warm water that
is normally located near Australia to move eastward along the
equator until it reaches the coast of South America.
"The collapse of the trade winds and the depression of the
thermocline (cooler water) resulted in an increase of sea surface
temperature and sea surface height in early 1997, and this
interaction appears to be the typical mechanism of equatorial
changes associated with an El Niño," Liu explained.
In addition to measuring the beginning of El Niño along the
equator, NSCAT also revealed that, when the trade winds weakened,
an unusual low-pressure system with cyclonic (counterclockwise)
circulation moved toward the North American coast. NSCAT
observed that winds branched off from the equator, bypassed
Hawaii, and brought heat and moisture from the tropical ocean
towards San Francisco via a route often called the "Pineapple
"This moist and warm air from the south kept evaporation
low and the ocean water warmer than normal near the North
American coast," Liu suggested. "This change brought with it
strong ecological changes, such as the tropical fish caught off
the coast of Oregon and the deaths of sea lions on the Channel
Islands in California."
An image of this "teleconnection" between the warming of
equatorial water associated with El Niño and the warming of the
North American coastal waters through wind patterns is available
at http://www.jpl.nasa.gov/elnino .
NSCAT was a radar instrument that flew on Japanís Advanced
Earth Observing Satellite (ADEOS) until the satellite suffered an
electrical failure and ceased functioning on June 30, 1997. JPL
is currently building the SeaWinds scatterometer that will fly on
the Quick Scatterometer (QuikScat) satellite set for launch in
November 1998 will continue the important wind
observations begun by NSCAT. SeaWinds will provide better
coverage of the ocean than NSCAT and will improve our ability to
observe the influence of El Niño from the equatorial water to
regions closer to our home, Liu said.
The scatterometery program is managed by JPL for NASAís
Earth Sciences Enterprise, Washington, D.C. JPL is managed for
NASA by the California Institute of Technology.