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June-July 2007

short takes

An overview of projects throughout the organization

Science-society insight from Hurricane Rita. An interdisciplinary team of NCAR scientists is launching a major new program known as Atmospheric Composition Remote Sensing and Prediction (ACRESP). The program will focus on integrating satellite data into Earth system models and determining what new satellite observations will be required in the future to address key science questions. The initiative, which is led by Dave Edwards (ESSL/ACD) with researchers in ESSL/CGD and CISL/IMAGe, is expected to encompass additional NCAR laboratories in time. It also involves the wider university and agency community. Funding comes from the NCAR directorate and NASA.
An important component of the new program is the development of a chemical weather forecasting capability that is analogous to weather forecasting. Such outlooks could eventually provide communities with several days’ notice of high levels of smog, particulate matter, or other air quality issues important to human health. Field campaigns that look at atmospheric chemistry and air quality will also have access to chemical forecasts for aircraft flight planning.
Chemical weather forecasting will require a better understanding of the evolution of ozone, particulates, and other pollutants, as well as the local impact of pollutants transported from distant sources. The research can reveal connections between climate change and regional air quality.
The scientists plan to integrate data from satellites, aircraft, and ground stations into global and regional chemistry transport models such as MOZART (Model for Ozone and Related Chemical Tracers), and CAM-Chem and WRF-Chem (the chemistry versions of the Community Atmosphere Model and Weather Research and Fore­casting model), using the Data Assimilation Research Testbed (DART). Satellite observations play a key role in chemical weather forecasts because they are able to provide a large-scale view of the evolving distributions
of pollutants.
Other activities within ACRESP will investigate the ways that current satellite data can be used to evaluate and perhaps improve the performance of Earth system models. These same models will be used to simulate the observations of future satellite instruments, thereby helping researchers determine which prospective instruments and measurements would be most useful in shedding light on important atmospheric processes. The ultimate goal is to provide NCAR and the wider community with a laboratory that will help in the design of future satellite missions.

Iron deposition in the ocean. Iron, a critical nutrient for microorganisms in the oceans, helps sustain marine ecosystems. While iron can come from desert dust and other naturally occurring airborne particles, Natalie Mahowald (ESSL/CGD) and a team of collaborators are studying whether marine regions also benefit from iron that is emitted from industrial burning and wildfires.

Natalie and colleagues for the first time modeled the sources, transport, and deposition of iron from combustion sources. The researchers also analyzed daily emissions measurements at a site in Korea located near sources of both dust and industrial emissions. One of their goals was to distinguish between the deposition of insoluble and soluble iron, as soluble iron is probably the only form that marine organisms can absorb.

Since iron from mineral sources is 30 times more prevalent than iron from combustion sources, it would seem that combustion iron plays a small role in marine ecosystems. Indeed, the modeling suggests that combustion sources contribute less than 5% of the iron in many open ocean areas, although it may account for slightly more than 20% near Asia. However, the observations in Korea of airborne dust and particles from industrial emissions indicate that, depending on how soluble and insoluble iron is processed in the atmosphere, combustion may actually be producing 20% to as much as 100% of the soluble iron that’s deposited in many ocean regions.

Natalie and her collaborators believe that the reason has to do with the incomplete combustion of black carbon, which would mean that soluble iron is being emitted directly into the atmosphere. This would indicate that in many ocean regions, combustion sources may be more important than dust and other naturally occurring particles for fertilizing the oceans.

Alfvén waves observed. ESSL/HAO’s Steve ­Tomczyk published a paper in the August 31 issue of ­Science documenting the first observations of elusive oscillations in the Sun’s corona (outer layer) known as Alfvén waves.
The waves transport energy outward from the surface of the Sun. Unlike other waves, they do not lead to large-intensity fluctuations in the corona, making them difficult to detect. In addition, their velocity shifts are small and not easily spotted. Although they have been detected in the heliosphere outside the Sun, they had never before been viewed within the corona.
Steve and a team of researchers that included Scott McIntosh (Southwest Research Institute) and Phil Judge (ESSL/HAO) used the Coronal Multichannel Polarimeter, or CoMP, to gather and analyze light from the Sun’s corona. CoMP, which utlilizes a telescope at the National Solar Observatory in Sacramento Peak, New Mexico, tracks magnetic activity around the entire edge of the Sun and collects data with unusual speed.
The instrument enabled the research team to capture intensity, velocity, and polarization images of the solar corona. The images revealed Alfvén waves that moved in trajectories aligned with magnetic fields and traveled as fast as nearly 2,500 miles (4,000 kilometers) per second.
The discovery is expected to give researchers more insight into the fundamental behavior of solar magnetic fields, eventually leading to a fuller understanding of how the Sun affects Earth and the solar system.
For more, visit www.ucar.edu/news/releases/2007/

doppler velocity

Scientists have observed elusive oscillations in the Sun’s corona, known as Alfvén waves, for the first time. In this image, made by NCAR’s CoMP instrument, the oscillations of the plasma velocity are made clearer by filtering the velocity data to show only oscillations that recur periodically every five minutes. (Image courtesy Steve Tomczyk and Scott McIntosh.)

Hazardous plumes. For several years, RAL scientists have worked with Department of Homeland Security officials to create fine-resolution models that can simulate the tracks of hazardous plumes through the atmosphere. Now they are looking at the problem in a different way: detecting a hazardous plume and backtracking to the source of the plume.
The goals of this approach are to fully map out the area that may be affected by the plume, gain insights into the material being released into the atmosphere, and possibly determine who is releasing the material. If an industrial plant is on fire, for example, researchers can use the model to help determine the rate at which toxins are being released and the area that should be evacuated. If terrorists release dangerous chemical, biological, or radioactive (CBR) substances, first responders can use the models both to evacuate residents in the path of the plume and to determine where the terrorists were operating.
RAL’s Paul Bieringer and George Bierberbach
are heading up the project, known as Sensor Data
Fusion. Other scientists on the team include Francois Vandenberghe, Andrzej Wyszogrodzki, and Rong-Shyang Sheu (all in RAL), and Jeff Weil (ESSL/MMM).
Their aim is to assimilate observations of winds, temperatures, and other atmospheric properties, along with measurements from CBR sensors, into transport and ­dispersion models. These models, which are capable of operating at horizontal grid increments of 5 to 10 meters (16 to 33 feet), will ultimately improve the hazard prediction capabilities of the departments of Defense and Homeland Security. Funding for the project comes from the Defense Threat Reduction Agency.

WACCM reaches higher. NCAR’s Whole-­Atmosphere Community Climate Model (WACCM) is a comprehensive numerical model that spans the range of altitude from Earth’s surface to the outer atmosphere. An interdivisional effort in ESSL, WACCM incorporates HAO’s modeling of the upper atmosphere, ACD’s modeling of the middle atmosphere’s chemistry, and CGD’s modeling of atmospheric dynamics and the lowest portion of
the atmosphere.
Hanli Liu (HAO/TIIMES) and a team of colleagues are working to increase WACCM’s reach to higher altitudes. Over the past year, they’ve extended the model from 87 miles (140 kilometers) to 310 mi (500 km). The new ­domain now incorporates the upper thermosphere (fourth layer of the atmosphere).
The team’s next step is to include the ionosphere (the ionized region of the thermosphere) in WACCM. When the work is complete in about a year, researchers will have a more complete model of the whole atmosphere, which they’ll begin using to tackle scientific problems.
The integrated model will help scientists better understand climate change throughout the whole atmosphere. This is especially important because carbon dioxide emissions impact the upper atmosphere as well as the lower. The model will also provide scientists with a numerical tool to connect tropospheric climate with space weather and to study lower and upper atmospheric coupling.

Nitrogen and climate. A team of researchers in ESSL/CGD, led by Peter Thornton, is expanding our ­understanding of the climate system by adding the nitrogen cycle to the Community Climate System Model (CCSM). Nitrogen has critical influences on the atmosphere, in part because it enables plants to grow and take in carbon dioxide.
Preliminary research, now in press, with the land component of CCSM shows that nitrogen has complex and sometimes conflicting impacts on global warming. One of the most important findings is that the limited supply of nitrogen, an essential plant nutrient, will restrict the ability of plants to absorb carbon dioxide from the atmosphere. Whereas carbon-only models have indicated that plants would partially offset warming temperatures by thriving in a world of higher atmospheric carbon dioxide levels, the new research indicates that plants won’t have the requisite nitrogen to grow as much as climate scientists thought.
Although that is bad news for the planet, it is partially offset by another preliminary finding. Peter and his colleagues are discovering that increased levels of atmospheric carbon dioxide, and associated climate change, will stimulate more uptake of carbon on land. That is because in a warmer and, in some places, wetter climate, decomposition will provide plants with more nitrogen, which will boost plant growth. In contrast, previous carbon-only models had predicted reduced uptake of carbon on land.
The results of this complex line of research, including an examination of the interplay between nitrogen and land cover changes, won’t be resolved for at least several months. Early indications, however, show that carbon dioxide levels in the atmosphere are likely to rise at least somewhat more quickly than indicated by carbon-only models, including those cited by the Intergovernmental Panel on Climate Change. Another likely result is that tropical ecosystems will play an especially critical role in absorbing rising amounts of carbon dioxide.•

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