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June
26, 2007 Scientists from
NOAA's Earth System Research Lab will
be
among 400 researchers in The Tropical
Composition, Cloud and Climate
Coupling (or "TC4") experiment will use a large array of instruments
to observe a part of the atmosphere above the eastern ESRL’s
David Fahey and colleagues from NOAA
and the University of Colorado will
fly instruments aboard NASA’s high-altitude WB-57 aircraft to
gather data
on black carbon particles, ozone, water vapor and particle composition,
as well
as air pressure and temperature. “We’ll
be fishing around in a key part of the
atmosphere at a key time of year,” said Fahey.
“Casting a wide net and being
open to whatever comes could lead to surprising and important
findings.” Fahey will observe
black carbon, or soot,
produced by fossil fuel burning. By absorbing sunlight and heating the
air,
black carbon can change atmospheric circulation and precipitation, but
the
processes involved are unclear. For example, how black carbon
influences clouds
and how clouds remove it from the atmosphere remain an unsolved puzzle.
Scientists know so little about black carbon that any direct
observations are
important, Fahey said. On the same aircraft, a team led by
NOAA/ESRL
scientist James Elkins will measure nearly 20 gases, including
ozone-destroying
chlorofluorocarbons and their substitutes, the greenhouse gas methane,
carbon
monoxide, and peroxyacytyl nitrate (also known as PAN) — a
component of smog at
lower altitudes. Elkins will track natural and human-produced PAN as it
moves
over land, changes altitudes, then travels long distances. It finally
descends
over the ocean, forming surprisingly high levels of ozone above the
remote,
pristine Pacific.
Elkins will also
monitor methyl iodide,
another compound with little known about it. Depending on the lifetime
of the
gas, an iodine atom can attack Earth’s protective ozone layer
200 times more
effectively than a chlorine atom, the primary ozone destroyer. How much
methyl
iodide is getting into the stratosphere and exactly how it gets there
are
unknown. “Until
recently, we thought oceans were the
only important source of methyl iodide. Now we know the Amazon can be a
big
source,” Elkins said. “We now have to look into
what it means for the ozone
layer.” Among substitutes
for human-made
ozone-depleting compounds, Elkins will study HCFC-22. Commonly used in
room air
conditioners, the compound was introduced as a shorter-lived,
less-harmful
substitute for ozone-eating chlorofluorocarbons, but it’s
also a greenhouse
gas. Now levels of HCFC-22 are rising rapidly as the demand for air
conditioning soars in Water vapor, the
most powerful and most
prevalent greenhouse gas, is a primary focus of TC4. In the study layer
of the
lower stratosphere, air is far drier than at the surface, but the exact
numbers
are questionable. Six water vapor instruments on board the WB-57 will
help
scientists verify satellite data and resolve inconsistencies found in
previous
measurements. Holger
Vömel with the Cooperative Institute for Research in
Environmental Sciences (also known as CIRES), a partnership between
NOAA and the The total stream
of TC4 measurements from
space, aircraft, balloons and ground stations will help researchers
understand
their own data and provide long-awaited accuracy checks for satellite
instruments. “Everyone wants to know how accurate the
satellites are,” says
Fahey. “It’s incredibly important.” The National
Oceanic and Atmospheric
Administration, an agency of the U.S. Commerce Department,
is celebrating 200 years of science and service to the nation. From the
establishment of the Survey of the Coast in 1807 by
Thomas Jefferson to the formation of the Weather Bureau and the
Commission of
Fish and Fisheries in the 1870s, much of NOAA is dedicated
to enhancing economic
security and national safety through the prediction and research of
weather and
climate-related events and information service delivery for
transportation, and
by providing environmental stewardship of our nation's coastal and
marine
resources. Through the emerging Global Earth Observation System of
Systems (GEOSS), NOAA is working with its federal
partners, more than 60 countries and the European Commission to develop
a
global monitoring network that is as integrated as the planet it
observes,
predicts and protects. CIRES is a partnership between NOAA and the ##
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