Campus: CSU Los Angeles -- January 28, 2004
Dictates Droughts and Drenching - Study by Cal State L.A. Professor,
Grad Student and JPL Researcher Predicts Drier and Cooler Temperatures
in Southern California
The cooler and drier conditions in Southern California over the last
few years appear to be a direct result of a long-term ocean pattern
known as the Pacific Decadal Oscillation, according to research presented
recently at the 2004 meeting of the American Meteorological Society.
The study by Steve LaDochy, associate professor of geography at California
State University, Los Angeles; Bill Patzert, research oceanographer
at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California;
and Jeff Brown, graduate student in geography at Cal State L.A., suggests
Pacific oceanic and atmospheric measurements can be used to forecast
seasonal West Coast temperatures and precipitation up to a year in advance,
from Seattle to San Diego.
An important climate controller, the Pacific Decadal Oscillation is
a basin-wide oceanic pattern similar to El Niño and La Niña
but much larger. The pattern lasts many decades rather than just a few
months like El Niño and La Niña. The climatic fingerprints
of the pattern are most visible in the North Pacific and North America,
with secondary influences coming from the tropics. The long-term nature
of the pattern makes it useful for forecasting, as its effects persist
for so long.
Since mid-1992, NASA has been able to provide space-based, synoptic
views of the entire Pacific Ocean’s shifts in heat content with
the Topex/Poseidon mission and its follow-up mission, Jason (which began
in 2001). Before these satellites were available, monitoring oceanic
climate signals in near-real time was virtually impossible.
The remarkable data and images can tag and monitor the shifts in short-term
climate events, like El Niño and La Niña, and long-term
events such as the Pacific Decadal Oscillation. These data provide a
13-year continuous, complete time-series containing two major El Niños
and two La Niñas, and have made it possible to detect a major
phase shift of the Pacific Decadal Oscillation. Patzert and LaDochy
show these data, combined with longer-term studies of land-based data,
provide a powerful set of forecasting tools.
The pattern shifted to a negative, cool phase, leading to wetter conditions
in the U.S. Pacific Northwest, and drier than normal conditions in Central
and Southern California this decade. Since the last El Nino in 1997-1998,
the Los Angeles area has had only 79 percent of its normal rainfall,
Patzert said. Lake Mead, the great fresh-water reservoir in southeast
Nevada, is at less than 50 percent of normal capacity. Also, huge West
Coast fires over the past few years have been greatly exacerbated by
drought induced by the pattern, Patzert added.
“These shifts in the pattern are long-term tendencies, which actually
have a bigger economic impact than El Niño,” said Patzert.
“People talk about floods from El Niño, but what really
has a harsh and costly impact is a five-year drought.”
“A full cycle of the Pacific Decadal Oscillation (cool to warm
and back to cool) runs about 50 years,” said LaDochy. “Over
the next several years there is going to be a tendency toward dry and
cooler temperatures in the southern U.S. West Coast. It is very difficult
to forecast day-to-day here on the West Coast, but we can say with some
confidence that over the next five years, we’d better start saving
The researchers used over 50 years of U.S. climatic information, and
Pacific atmospheric and oceanic data from the National Oceanic and Atmospheric
Administration’s National Centers for Environmental Prediction.
By comparing data sets, they saw strong correlations between Pacific
climate patterns, temperatures and precipitation trends on the West
Coast. They then were able to develop “hindcasts” to explain
temperature and precipitation variability for West Coast regions. These
decadal cycles also will be useful for explaining future regional climate
Steve LaDochy, associate professor of geography at Cal State L.A., received
his Ph.D. from the University of Manitoba. LaDochy is a climatologist
and meteorologist, with special interests in thunderstorm phenomena
and synoptic climatology. He also conducts research in air pollution,
weather forecasting, lightning and urban climates.
For images about the research on the Internet, visit the NASA (National
Aeronautics and Space Administration) Web site at: <http://www.gsfc.nasa.gov/topstory/2004/0116westcoast.html>.
(JPL is managed for NASA by the California Institute of Technology in
Pasadena.) For further details on the research, contact Alan Buis, Jet
Propulsion Laboratory, Pasadena, CA, (818) 354-0474; Elvia H. Thompson,
NASA Headquarters, Washington, DC, (202) 358-1696; or Krishna Ramanujan,
Goddard Space Flight Center, Greenbelt, MD, (607) 273-2561.
MEDIA CONTACT: Carol Selkin, Media Relations Director,
Cal State L.A., (323) 343-3044