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May 1,2003
NASA Discovers a Soggy Secret of El Niño
NASA-funded researchers have discovered El Niño's soggy secret.
When scientists identified rain patterns in the Pacific Ocean, they discovered
the secret of how El Niño moves rainfall around the globe during
the life of these periodic climate events when waters warm in the eastern
Pacific Ocean.
The results may help scientists improve rainfall forecasts around the
globe during the life of an El Niño, and may also offer new insights
into how an El Niño develops.
The findings were highlighted in a paper authored by Scott Curtis of
the University of Maryland - Baltimore County, Baltimore, Md., and Bob
Adler, of Goddard Space Flight Center, Greenbelt, Md. The study appeared
in a recent issue of the American Geophysical Union's Journal of Geophysical
Research.
In an effort to predict and understand the effects of El Niño,
most scientists focus on seasonal changes in rainfall patterns, like
where and when rain falls during winter. This study takes a different
approach by first looking at the evolution of rainfall over the geographic
area of the Pacific, which has the power to change the global winds and
re-direct rainfall patterns around the world.
Curtis and Adler found a significant pattern of alternating rainfall
for El Niños since 1979, with wetness in eastern China, dryness
over Indonesia and wetness in the south Indian Ocean and Australia.
They noted that this pattern swings eastward as the El Niño weakens.
As El Niño weakens, rainfall patterns alternate from one area
to another. In the eastern Pacific, there is wetness on the Equator,
dryness off the coast of Mexico, and wetness off the coast of California.
The traditional view of El Niño based on seasonal rainfall patterns
obscures these relationships.
El Niño events, like individual thunderstorms, differ in intensity,
lifespan, rainfall, and other characteristics, making them difficult
to quantify. So, Curtis and Adler had to set parameters to define El
Niños based on rainfall that occurs in the equatorial Pacific.
They looked at the periods before rainfall began, when the El Niño
started, peaked, faded, and after it ended. They also identified areas
around the globe that were consistently wet or dry during each El Niño
evolution stage.
Curtis and Adler utilized global rainfall datasets developed from satellites
and rain gauges from all over the world, which are part of the Global
Precipitation Climatology Project under the Global Energy and Water Cycle
Experiment (GEWEX), a project heavily supported by NASA.
Data from the Tropical Rainfall Measuring Mission (TRMM) satellite,
used in this study, will also help ensure the accuracy of satellites
used by the National Oceanic and Atmospheric Administration (NOAA) and
Department of Defense. TRMM is a joint NASA/Japanese Space Agency mission
to study tropical rainfall and its implications for climate. Each day,
the TRMM spacecraft observes the Earth's equatorial and tropical regions.
In the future this kind of study will help pinpoint where an El Niño
will generate floods, droughts, and changes in rainfallaround the globe.
This information will be extremely useful once NASA's Global Precipitation
Measurement mission, currently in formulation launches sometime after
2007.
This NASA funded work addresses a number of NASA's Earth Science Enterprise
research strategies, including how variations in local weather, precipitation
and water resources are related to global climate variation, in this
case caused by El Niño. By recognizing global rainfall patterns
associated with El Niño and by better understanding the impacts
of El Niño, researchers may be able to better understand and predict
these climate variations.
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Contacts:
Rob Gutro
Goddard Space Flight Center
(Phone: 301-286-4044)
Chip Rose
University of Maryland-Baltimore County
(Phone: 410-455-5793)
Harvey Leifert
American Geophysical Union
(Phone: 202/777-7507) |
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 El
Niño's Peak Rain in Red
Areas that are wet (red) or dry (blue) during the wintertime
(December-January-February) during the peak of El Niño. CREDIT:
NASA
 El
Niño Post-Peak - Red Areas Become Wet
Areas that go from dry to wet (red) or wet to dry (blue)
from the summer before the El Ni¤o peak to the summer after the El Niño
peak. This is the traditional view of El Niño evolution. CREDIT:
NASA
 Precipitation
Peak of El Niño - in Red
This image shows wet areas (red) or dry areas (blue)
when the central Pacific is very wet and Indonesia is very dry (the "precipitation" peak
of El Niño). CREDIT: NASA
 Precipitation
Past El Niño Peak - in Red
Areas pictured go from dry to wet (red) or wet to dry
(blue) from six months before this type of El Niño peak to six
months after the El Niño peak. This is a new view of El Niño
evolution. CREDIT: NASA
 Quicktime
Animation
The 1997 El Niño warm waters in the Pacific Ocean
are red; the decrease of red and increase of cooler water signals the
La Niña of 1998. Credit: NASA
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