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December 2006 - January 2007

short takes

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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