Scientists Surf the Seas of Space to Catch an Atmospheric Wave(Forwarded)

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Alan Buis (818) 354-0474
Jet Propulsion Laboratory, Pasadena, Calif.

February 2, 2006

News Release: 2006-017

Scientists Surf the Seas of Space to Catch an Atmospheric Wave

A study by NASA and university scientists is shedding new light on a
mysterious, cyclical wave in Earth's atmosphere that at times profoundly
affects our planet's weather and climate.

Using satellite data from the Atmospheric Infrared Sounder (Airs)
instrument on NASA's Aqua spacecraft, a research team led by Dr. Duane
Waliser of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and Dr.
Baijun Tian of the California Institute of Technology, also in Pasadena,
set out to study the structure and evolution of the Madden-Julian
Oscillation.

This slow, eastward-moving wave of clouds, rainfall and large-scale
atmospheric circulation anomalies spans nearly half of Earth's equator,
primarily over the Indian Ocean and western Pacific. Because it can
strongly influence long-term weather patterns and has far-reaching global
effects, scientists want to incorporate it more accurately in the general
circulation models used by agencies around the world for weather
prediction and climate forecasts.

Ebbing and flowing in cycles of about 40 to 50 days, the Madden-Julian
Oscillation triggers showers and thunderstorms as it forces air to rise,
and it inhibits clouds and rainfall in its subsiding phase. Its impacts
are widespread. It triggers Asian and Australian monsoon wet and dry
spells in the Indian and western Pacific oceans. It affects the winter jet
stream and atmospheric circulation in the Pacific/North America region,
causing anomalies that can lead to extreme rainfall events. It can also
change summer rainfall patterns in Mexico and South America and may
trigger variations in the El Nino climate phenomenon.

The Airs analysis revealed the oscillation results in an elegant interplay
between rainy and clear conditions over the tropical Indian and western
Pacific Oceans. Warm and moist conditions near the surface eventually give
way to rainy and cloudy conditions aloft. These disturbed conditions are
ultimately squelched by the introduction of dry, cool air near the
surface, leading to clear skies. The rainy, clear and transitional periods
in between them last 10 to 12 days each.

"Details such as these are critical for evaluating weather prediction
models and improving our theoretical understanding of the oscillation
phenomena," said Waliser. "Temperature and moisture data from sparse
weather balloon readings and atmospheric models are simply not sufficient
to properly represent many important features of the oscillation.
Satellite-based observations such as those from Airs are therefore
fundamental to gaining a fuller understanding of the processes at work."

The research team combined 3-D atmospheric moisture and temperature
profiles from Airs from September 2002 to January 2005 with rainfall data
from the joint NASA/Japan Aerospace Exploration Agency Tropical Rainfall
Measurement Mission from January 1998 to February 2005. The rainfall data
were used to identify Madden-Julian Oscillation events.

Waliser said that until recently, modeling the wave's hydrological
components such as water vapor and clouds, condensation and evaporation
processes has been difficult. With the launch of Airs in 2002, however,
scientists gained a far greater ability to examine the wave's structure in
3-D and study its evolution over space and time.

"The high-quality Airs water vapor and temperature profiles provide new
information on the vertical structure of the Madden-Julian Oscillation,"
said Tian. "This new information allows us to study the meteorological
components that make up the oscillation in a way never before possible."

Airs is a high-spectral resolution infrared instrument that gathers 3-D
profiles of atmospheric temperatures, water vapor and trace gases. It is
the first in a series of advanced infrared sounders that will provide
accurate, detailed atmospheric temperature and moisture observations for
weather and climate applications. It views the atmosphere through nearly
2,400 different spectral channels, collecting 144,000 data retrievals
daily around the globe.

The Tropical Rainfall Measurement Mission monitors tropical rainfall. The
mission is the first space-based platform that uses microwaves along with
precipitation radar to probe through clouds to reveal their vertical
structure and estimate how much rainfall they are producing. The data are
invaluable in areas with no rain gauges, such as the open ocean.

Study results were presented this week at the American Meteorological
Society 86th Annual Meeting in Atlanta.

For more information on the Web, visit:
http://airs.jpl.nasa.gov/
or
http://trmm.gsfc.nasa.gov/

For information about NASA and agency programs on the Web, visit:
http://www.nasa.gov/home/

JPL is managed for NASA by the California Institute of Technology in
Pasadena.