‘La Nada’ climate pattern lingers
New remote sensing data from
NASA’s Jason-2 satellite show
near-normal sea-surface height
conditions across the equatorial
Pacific Ocean. This neutral, or
“La Nada” event, has stubbornly
persisted for 16 months, since spring
2012. Models suggest this pattern will
continue through the spring of 2014,
according to the National Weather
Service’s Climate Prediction Center.
“Without an El Niño or La Niña signal
present, other, less predictable,
climatic
factors
will
govern
fall, winter and spring weather
conditions,” said climatologist Bill
Patzert of NASA’s Jet Propulsion
Laboratory, Pasadena, Calif. Longrange forecasts are most successful
during El Niño and La Niña episodes.
The “in between” ocean state, La
Nada, is the dominant condition,
and is frustrating for long-range
forecasters. It’s like driving without
a decent road map -- it makes
forecasting difficult.”
The
near-normal
conditions
are shown in a new image (as
areas shaded in green), based on
the average of 10 days of data
centered on Aug. 27, 2013.
For the past several decades,
about half of all years have
experienced La Nada conditions,
compared to about 20 percent for
El Niño and 30 percent for La Niña.
Patzert noted that some of the
wettest and driest winters occur
during La Nada periods.
“Neutral infers something benign,
but in fact if you look at these La
Nada years when neither El Niño
nor La Niña are present, they can
be the most volatile and punishing.
As an example, the continuing,
deepening drought in the American
West is far from ‘neutral,’” he said.
The height of the sea water
relates, in part, to its temperature,
and thus is an indicator of the
amount of heat stored in the ocean
below. As the ocean warms, its level
rises; as it cools, its level falls. Yellow
and red areas indicate where the
waters are relatively warmer and
Artist’s concept of the Jason-2 spacecraft in space.
have expanded above normal
sea level, while green (which
dominates in this image) indicates
near-normal sea level, and blue
and purple areas show where the
waters are relatively colder and sea
level is lower than normal. Abovenormal height variations along the
equatorial Pacific indicate El Niño
conditions, while below-normal
height variations indicate La Niña
conditions. The temperature of the
upper ocean can have a significant
influence on weather patterns
and climate. For a more detailed
explanation of what this type of
image means, visit: http://sealevel.
jpl.nasa.gov/science/elninopdo/
latestdata/.
This latest image highlights the
processes that occur on time scales
of more than a year, but usually
less than 10 years, such as El Ni