Wind data for the Pacific Ocean obtained by NASA’s Quick
Scatterometer spacecraft — also know as Quikscat — are documenting
episodes of reversed trade winds that are responsible for
unseasonable cyclone conditions in the northwest and southwest
Pacific, and which may be a precursor of a future El Niño.

A research team led by Dr. W. Timothy Liu, a senior
research scientist at NASA’s Jet Propulsion Laboratory in
Pasadena, Calif., used wind speed and direction data from
Quikscat to detect a shift in the trade winds on February 25.
The winds shifted from their normal easterly direction to a
westerly direction, blowing from Indonesia toward the Americas
along the equator. This trade wind shift, which lasted for
about a week, contributed to the spawning of twin cyclones–
Super Typhoon Mitag, which threatened the Philippines; and
Tropical Cyclone Des, which passed through New Caledonia.

“In addition to unusual cyclonic activity, such trade
wind reversals typically trigger Kelvin waves of warm water,
which can be an early indicator of future El Niño conditions,”
said Liu. “During periods of reversed trade winds, which
typically last from a few days to a week or more, equatorial
westerly winds generate a counterclockwise vortex in the
northern hemisphere and a clockwise vortex in the southern
hemisphere. Once spawned, the resulting Kelvin waves may
travel across the Pacific and reach the coastline of the
Americas in approximately one to two months, warming the
waters of the eastern Pacific and creating El Niño conditions
when the effects are accumulated.”

Sustained Kelvin wave activity could have a major impact
on global weather patterns according to JPL oceanographer Dr.
William Patzert. “If trade wind patterns continue to
experience reversals through the spring and summer, the
resulting strong, warm Kelvin waves will cross the Pacific
like a conveyor belt, depositing warm water near South America
where the ocean is normally cold,” he said. “Such a ‘warm
pool’ could alter weather all over the planet, with rains that
would normally soak the western Pacific shifting toward the
Americas, and places such as Indonesia and India becoming
drier. We’re really in a ‘wait and see’ situation at this

A similar westerly wind flow and twin cyclones were
documented by Liu and his team using Quikscat data last
December. The wind reversal at that time, which lasted 10
days, triggered a Kelvin wave that just recently reached South
America, as revealed by NASA’s Topex/Poseidon satellite.

The Quikscat images are available at: .

More details of the two westerly winds events can be
found at: .

Launched June 19, 1999, the Quikscat spacecraft operates
in a Sun-synchronous, 800-kilometer (497-mile) near-polar
orbit, circling Earth every 100 minutes, taking approximately
400,000 measurements over 93 percent of Earth’s surface every

In recent years, data from JPL’s Quikscat scatterometer
have proven useful in improving forecasts of extreme wind
events, such as hurricanes, and in monitoring longer-term
climatic effects such as El Niño. Quickscat’s SeaWinds
scatterometer instrument is a specialized microwave radar that
continuously measures both the speed and direction of winds
near the ocean surface in all weather conditions.

JPL manages Quikscat for NASA’s Office of Earth Science,
Washington, D.C. JPL also built the scatterometer instrument
and provides ground science processing systems. NASA’s
Goddard Space Flight Center, Greenbelt, Md., managed
development of the satellite, designed and built by Ball
Aerospace & Technologies Corp., Boulder, Colo.

More information on Quikscat is available at: .

The U.S.-French Topex/Poseidon mission has been making
precise measurements of ocean surface topography since 1992.
These data are used to map ocean currents, improve the
understanding of ocean circulation, measure global sea level
change and improve global climate forecasts. Topex/Poseidon’s
ability to measure sea-surface height has made it an
invaluable tool for studying ocean events such as El Niño, its
little sister La Niña and the much larger and longer-lasting
ocean event called the Pacific Decadal Oscillation.
Topex/Poseidon is managed by JPL for NASA’s Earth Science
Enterprise, Washington, D.C.

More information on Topex/Poseidon is available at: .

NASA’s Earth Science Enterprise is a long-term research
and technology program designed to examine Earth’s land,
oceans, atmosphere, ice and life as a total integrated system.