A NASA Space Sleuth Hunts the Trail of Earth's Water (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.

Adriana Bailey/Jim Scott 303-492-6289/3114
University of Colorado, Boulder, Colo.

January 31, 2007

News Release: 2007-009

A NASA Space Sleuth Hunts the Trail of Earth's Water

For the first time, NASA scientists have used a shrewd spaceborne detective
to track the origin and movement of water vapor throughout Earth's
atmosphere. This perspective is vital to improve the understanding of
Earth's water cycle and its role in weather and climate.

NASA's newest detective in the mysteries of atmospheric water vapor is the
Tropospheric Emission Spectrometer instrument on the Aura satellite. A team
of scientists from NASA's Jet Propulsion Laboratory, Pasadena, Calif., and
the University of Colorado, Boulder, used the instrument's observations of
heavy and light water vapor to retrace the "history" of water over oceans
and continents, from ice and liquid to vapor and back again. Heavy water
vapor molecules have more neutrons than lighter ones do.

By analyzing the distribution of the heavy and light molecules, the team was
able to deduce the sources and processes that cycle water vapor, the most
abundant greenhouse gas in Earth's atmosphere.

The team found that tropical rainfall evaporation and water "exhaled" by
forests are key sources of moisture in the tropical atmosphere. They noted
that more water than they had expected is transported over land rather than
ocean into the lower troposphere (Earth's lowermost atmosphere), especially
over the Amazon River basin and tropical Africa.

"One might expect most of the water to come directly from the wet ocean,"
said study co-author Dr. David Noone of the University of Colorado.
"Instead, it appears that thunderstorm activity over the tropical continents
plays a key role in keeping the troposphere hydrated."

The team found that in the tropics and regions of tropical rain clouds,
rainfall evaporation significantly adds moisture to the lower troposphere,
with typically 20 percent and up to 50 percent of rain there evaporating
before it reaches the ground. The atmosphere retains this water, which can
be used to make clouds. The strength and location of this evaporation give
scientists new insight into how water in Earth's atmosphere helps move
energy from Earth's surface upwards. The main role of the atmosphere in
Earth's climate system is to take energy deposited by the sun and dispose of
it back into space.

The team also found evidence that water transported upwards by thunderstorm
activity over land originates from both plant "exhalation" in large forests
and evaporation over nearby oceans. The balance between these two different
sources tells us how vegetation interacts with climate and helps maintain
regional rainfall levels.

"This link between vegetation, hydrology and climate has implications for
how societies choose to manage their ecological resources," said Noone. "Our
measurements provide a baseline against which future changes in
vegetation-climate interactions can be measured."

The details of this journey are critical for understanding clouds and
climate, as well as changes in precipitation patterns and water resources,
Noone explained. "Our study measures the conditions under which
precipitation and evaporation occur, providing insights into the processes
responsible. Better knowledge of these processes ultimately leads to a
clearer understanding of the factors that drive the global water cycle and
its importance in climate and global climate change."

Noone and his co-authors said there has been a general lack of information
on the way water moves around in Earth's atmosphere -- where it comes from
and where it ends up.

"Since we measure the history of water, so to speak, we can tell the
difference between air masses that have undergone extensive condensation
from those that are more dominated by evaporation from the ocean surface,"
said study co-author Dr. John Worden of JPL.

"These results also lay the groundwork for research to help interpret the
isotopic measurements that scientists use to study Earth's climate in the
past," added JPL co-author Dr. Kevin Bowman.

Study results appear in the February 1 issue of the journal Nature.

For more on the Tropospheric Emission Spectrometer, visit:
http://www.nasa.gov/aura
and
http://tes.jpl.nasa.gov/

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