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December
2006 - January 2007
An
overview of projects throughout the organization
Climate
change affects upper atmosphere. A study
by ESSL/HAO’s Liying
Qian, Ray Roble, and Stan Solomon, along
with colleagues at The Pennsylvania State University,
predicts that carbon dioxide emissions from the burning
of fossil fuels will produce a 3% reduction in the
density of Earth’s outermost atmosphere by
2017.
Recent observations by scientists tracking satellite
orbits show that the thermosphere, which begins about
60 miles (100 kilometers) above Earth and extends
up to about 400 miles (650 kilometers), is beginning
to become less dense. The new study is the first
to analyze and confirm that this change will become
more pronounced over the next decade. The observations
also confirm predictions made in 1989 by Ray Roble
and Robert Dickinson (now at the Georgia Institute
of Technology) that the thermosphere would cool and
contract because of increasing carbon dioxide levels.
Although carbon dioxide emissions warm the lower
atmosphere, they have the opposite effect on the
thermosphere due to differences in density. Near
Earth’s surface, carbon dioxide absorbs radiation
escaping Earth, but before it can radiate the energy
to space, frequent collisions with other molecules
in the dense lower atmosphere force the carbon dioxide
to release energy as heat, thus warming the air.
In the much thinner thermosphere, a carbon dioxide
molecule absorbs energy when it collides with an
oxygen molecule, but there is ample time for it to
radiate energy to space before another collision
occurs. The result is a cooling effect.
The 11-year cycle of the Sun’s activity also
affects the thermosphere, producing a warming and
expansion during the active phase of the cycle, and
a settling and cooling when activity wanes. The research
team incorporated a new model of the solar cycle
developed by HAO’s Mausumi
Dikpati.
The study, which was published in Geophysical Research
Letters, is especially important because reduced
density in the thermosphere reduces the drag on satellites
in low-Earth orbit, allowing them to stay airborne
longer. Forecasts of upper-level air density could
help NASA and other agencies plan the fuel needs
and timing of satellite launches more precisely.
For more information, see the news
release.
Arctic sea ice melting rapidly. The extent of summer
sea ice in the Arctic Ocean could undergo surprisingly
rapid reductions in the future, according to new research led by Marika
Holland
(ESSL/CGD).
Working with colleagues at the University of Washington and McGill University,
Marika examined the impacts of greenhouse gas emissions on the Arctic. By analyzing
scenarios run with the Community Climate System Model, the team found that abrupt
sea ice reductions were a common feature in many model runs and could occur quite
early in the 21st century, as soon as about 2015. During these events (for which
it was assumed that emissions of greenhouse gases would continue at the current
rate), sea ice retreat was four times faster than at any time in the observed
record.
Click here or
on image to enlarge. |
Click here or
on image to enlarge. |
| The image at left, based on simulations produced
by the Community Climate System Model, shows the approximate extent of
Arctic sea ice in September. The model indicates the extent of this late-summer
ice could begin to retreat abruptly within several decades. By about 2040
(image at right), the Arctic may be nearly devoid of sea ice during the
late summer unless greenhouse gas emissions are significantly curtailed.
(Illustrations ©UCAR.) |
Rather than a gradual shrinking, the ice cover is projected to experience periods
of relative stability followed by abrupt retreat, according to the research.
Because open water absorbs more sunlight than ice, growing regions of ice-free
water will create a positive feedback mechanism that accelerates the warming
trend. In addition, global climate change is expected to drive warmer ocean currents
into the Arctic.
By examining multiple climate models and future emissions scenarios, the team
concluded that if emissions of carbon dioxide and other greenhouse gases were
to slow, the likelihood of rapid ice loss would decrease and the ice would probably
undergo a much slower retreat.
The study was published in the December 12 issue of Geophysical Research Letters.
For more information, see the news
release.
Graphical displays steer aircraft
away from icy skies. When ice builds up on an aircraft’s wings,
it can increase the drag on the airplane and make staying aloft more difficult.
Icing has caused a number of fatal plane crashes, perhaps the most famous of
them the 1959 crash that took the lives of rock ‘n’ roll legends
Buddy Holly, Ritchie Valens, and The Big Bopper (J.P. Richardson). Even when
aircraft are certified to fly through icing conditions, the risk can prompt pilots
to detour for hundreds of miles.
In early December, air traffic controllers, pilots, and other aviation weather
users began receiving detailed updates on in-flight icing in the form of graphical
displays. Developed by Marcia Politovich, who oversees RAL’s in-flight
icing research, and colleagues, the displays will increase safety and reduce
flight delays by guiding aircraft away from potentially hazardous icing conditions,
possibly saving the aviation industry up to $20 million per year from injuries,
aircraft damage, and fuel.
The displays are part of an upgrade to a system called CIP (Current Icing Product).
The new version, which is updated hourly with altitudes up to 29,000 feet (8,840
meters), incorporates advanced weather prediction models and more detailed observations.
Instead of simply indicating the potential for icing, it quantifies the probability
of icing encounters and their likely severity. Pilots of properly equipped aircraft
will be able to fly through areas of light icing instead of detouring around
wide regions with more severe icing conditions. Another major advance over the
previous version of CIP is that pilots will be able to access the maps in the
cockpit, helping them to make route adjustments as needed during flight.
The new version of CIP will especially benefit commuter planes and other smaller
aircraft, which are more vulnerable to icing hazards because they cruise at lower,
ice-prone altitudes below 18,000 feet (5,490 meters). In addition, they may lack
mechanisms common on larger jets that prevent ice buildup by heating the front
edges of the plane’s wings.
For more information, see
the news release.
New supercomputer more than doubles
NCAR’s computing capacity. CISL installed a new IBM supercomputer
in November known as blueice that more than doubles NCAR’s sustained
computing capacity. With a peak speed of 12 teraflops (12 trillion floating-point
operations per second), the new computer will enable scientists to enhance the
resolution and complexity of Earth system models, improve climate and weather
research, and provide more accurate data to decision makers.
In addition to its impressive peak speed, blueice is expected to deliver a sustained
performance of as much as 2 teraflops. Sustained performance, which measures
a system’s computational rate while running a workload of atmospheric,
oceanic, and geoscience models, is considered the best indicator of a system’s
usability. Blueice will be the organization’s first supercomputer to pass
this sustained-teraflop milestone.
The computer, which is the first phase of a system called the Integrated Computing
Environment for Scientific Simulation (ICESS), is undergoing acceptance testing
and will begin operations in February. A second phase of ICESS will be installed
in 2008. ICESS will provide computing support for the geosciences until mid-2011.
For more information see the news
release.
In this issue...
NCAR
scientists predict a warmer, wetter Earth
The
end of the world as we know it?
“A
New Light on Science”
Keeping
science in the news
Short Takes
Random
Profile: Chrystina Tasset
Delphi
Question: Webhire formatting issues
Just One Look
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