As Summer Starts, Next El Nino is Slwo to Grow

The Pacific Ocean doesn’t show signs of anything that looks like the
whopper El Niòo of 1997-1998, according to the latest information from the U.S.-
French ocean-observing satellite Topex/Poseidon. The data do show that the mid-
equatorial Pacific Ocean has slowly warmed by about 1 degree Celsius (33.8
degrees Fahrenheit) in the past few months. However, the Pacific continues to be
dominated by the larger-than-El Niòo/La Niòa pattern called the Pacific Decadal
Oscillation, which may discourage El Niòo development. The image is available at
http://www.jpl.nasa.gov/images/earth/pacificocean.

“Except for some recent mid-Pacific warming, June 2002 looks very much
like June 2001,” said oceanographer Dr. William Patzert of NASA’s Jet Propulsion
Laboratory, Pasadena, Calif. “We’re still in an El Niòo holding pattern.” (See
http://sealevel.jpl.nasa.gov/elnino/20010621.html for the June 2001 image.)

The ocean warming in the past month can be explained by a relaxation in
the equatorial trade winds observed by NASA’s Quick Scatterometer (QuikScat)
satellite, which measures ocean wind speed and direction. These winds usually
blow from the Americas towards Asia, helping push warm water eastward. “For the
first two weeks of June, these winds were unusually weak,” said Dr. Timothy Liu,
QuikScat project scientist. “But by last week, they had returned to normal. If the
weakening continued or intensified, we could have been expecting an El Niòo to
develop by early fall.” (See http://airsea-www.jpl.nasa.gov/ENSO/ .)

“For the past few winters the weather- and moisture-delivering jet stream
has been steered north by the Pacific Decadal Oscillation and other planetary
patterns, resulting in a warm winter all across the United States and very dry
conditions on the East and West coasts. A large enough El Niòo might provide
some relief for the drought-plagued west, southwest and southeast U.S., but it’s
wishful thinking so far,” Patzert added.

The Topex/Poseidon data were taken during a 10-day collection cycle
ending June 14, 2002. They show that there hasn’t been any fundamental change in
the ocean’s large-scale patterns for the past three years. The near-equatorial ocean
has been very quiet, although sea levels and sea-surface temperatures are near
normal or slightly warmer throughout the far western and central tropical Pacific.
Red areas are about 10 centimeters (4 inches) above normal; white areas show the
sea-surface height is between 14 and 32 centimeters (6 to 13 inches) above normal.
This warmth contrasts with the Bering Sea, Gulf of Alaska and U.S. West Coast,
where lower-than-normal sea-surface levels (blue areas) and cool ocean
temperatures continue. The blue areas are between 5 and 13 centimeters (2 and 5
inches) below normal, and the purple areas range from 14 to 18 centimeters (6 to 7
inches) below normal.

The Pacific has settled into a negative phase of the Pacific Decadal
Oscillation pattern for the past three years. This long-term ocean feature waxes and
wanes approximately every 20 to 30 years. In its present phase, a warm horseshoe
pattern of higher-than-normal sea-surface heights connects the north, west and
southern Pacific, while a cool wedge of lower-than-normal sea-surface heights is in
the eastern equatorial Pacific. (More information on the Pacific Decadal Oscillation
is available at http://topex-www.jpl.nasa.gov/elnino/20000118.html .)

Most recent National Oceanic and Atmospheric Administration sea-surface
temperature data also clearly illustrate the warming of the western and central
tropical Pacific and the persistence of the basin-wide Pacific Decadal Oscillation
pattern. They are available at
http://psbsgi1.nesdis.noaa.gov:8080/PSB/EPS/SST/climo.html .

The joint U.S.-French Topex/Poseidon and follow-on Jason 1 missions as
well as the QuikScat mission are managed by JPL for NASA’s Earth Science
Enterprise, Washington, D.C., dedicated to understanding the total Earth system and
the effects of natural and human-induced changes on the global environment.

More information on Topex/Poseidon and Jason 1 is available at
http://sealevel.jpl.nasa.gov/index.html . More information on QuikScat is available
at
http://winds.jpl.nasa.gov/missions/quikscat/quikindex.html .

National Oceanic and Atmospheric Administration seasonal weather
forecasts are available at http://www.noaanews.noaa.gov/stories/s794.htm .

JPL is a division of the California Institute of Technology in Pasadena.