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1997 research data reveal clues about El Niño's influence
June 2, 1998
This image displays wind measurements taken by the satellite-
borne NASA Scatterometer (NSCAT) during the last 10 days of May
1997, showing the relationship between the ocean and the
atmosphere at the onset of the 1997-98 El Niño condition. The
data have helped scientists confirm that the event began as an
unusual weakening of the trade winds that preceded an increase in
sea surface temperatures. The arrows represent wind speed and
direction while the colors indicate sea surface temperature. The
sea surface temperatures were measured by the Advanced Very High
Resolution Radiometer, a joint mission of NASA and the National
Oceanographic and Atmospheric Administration (NOAA). The trade
winds normally blow from east to west, but the small arrows in
the center of the image show the winds have changed direction and
are blowing in the opposite direction. The areas shown in red
are above normal sea surface temperatures -- along the equator,
off the west coast of the U.S., and along the west coast of
Mexico. This image also shows an unusual low pressure system with
cyclonic (counterclockwise) circulation near the western North
American coast. NSCAT also observed that winds associated with
this circulation pattern branched off from the equator, bypassed
Hawaii, and brought heat and moisture from the tropical ocean
towards San Francisco, in what is often called the "pineapple
express."
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