Geoscience Reference
In-Depth Information
and warmer air to the south. Low pressure systems tend to form beneath
the jet stream and move along with it, bringing wet storms from the Pacii c
Ocean into the western United States in the winter. During El Niño events,
the warm surface waters in the eastern Pacii c lead to a greater temperature
contrast farther south, pulling the jet stream southward and bringing more
storms into the Southwest. In contrast, during La Niña events, the eastern
Pacii c Ocean becomes even cooler than normal, reducing the temperature
contrast and therefore reducing the likelihood of a jet stream into this region,
decreasing the occurrence of storms and precipitation in the Southwest.
h
e 1997-1998 El Niño: Biggest on Record
El Niño events recur every two to seven years, at varying degrees of severity.
h e 1997-98 El Niño was the most heavily monitored and closely observed
climate event in history, and it taught climate scientists much of what they
know about the ENSO today. At the start of this event, unusually warm
waters began moving eastward across the equatorial Pacii c during the spring
of 1997, alerting major oceanographic and atmospheric research institutions
that a massive El Niño event was on its way. Researchers worldwide watched
as the wave of warm ocean waters made a rapid journey eastward across the
Pacii c, warming oceanic islands and coral reefs all along the way and reach-
ing the west coast of South America by August of that year.
Oceanographers and climatologists had already deployed an array of
buoys across the tropical Pacii c Ocean at er the monstrous 1982-83 El Niño
event had taken them by surprise. h ese buoys monitor water temperature
between the surface and a depth of 1,600 feet, wind speed and direction,
air temperature and humidity, and water movement (currents). h e data are
automatically relayed back to computers via the Argos satellite system and
are used to predict an upcoming El Niño event several months in advance,
which is the amount of time it takes for tropical ocean currents to respond
to changes in the trade winds.
In 1997, scientists were predicting deluges in Ecuador and Peru,
California, the Southwest, and throughout the southern United States, and
they expected droughts in the American Midwest, Brazil, Australia, and
Indonesia. h eir predictions were spot on, although the actual impacts were
signii cantly greater than anticipated. Storms in November 1997 generated
massive l ooding in southern Ecuador that let over three thousand people
homeless in minutes. Floodwaters also swept through coastal cities and
