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April 2006

short takes

An overview of projects throughout the organization

Mt. Pinatubo
The 1991 eruption of Mount Pinatubo did not affect ocean temperatures as dramatically as did the earlier eruption of Krakatoa. (Photo by T. J. Casadevall, U.S. Geological Survey.)

Volcanic impacts. The colossal eruption of the volcano Krakatoa in 1883 affected some aspects of Earth's climate system to a much greater degree than previously suspected. New research by a team of scientists, including CGD's Tom Wigley, indicates that the eruption cooled the oceans for many decades, partially offsetting warmer temperatures and associated sea level rise caused by human-related emissions of greenhouse gases during the 20th century.

The team, led by Peter Gleckler of Lawrence Livermore National Laboratory, used results from 12 climate models to analyze global ocean heat content from 1880 to 2000. The researchers compared six of the simulations that incorporated the effects of volcanic eruptions with six that did not. They found that the simulations that included volcanic eruptions corresponded far more closely with observations of ocean temperatures in the late 20th century than those in which eruptions were not included.

A surprising result was that the cooling influence of the Krakatoa eruption apparently persisted in the deep ocean for more than 100 years. The eruptions of other major volcanoes, such as Pinatubo in 1991, also produced persistent cooling signatures in the ocean, but their impacts were less striking. Part of the reason for this difference appears to be the warming effect of increasing greenhouse gas concentrations, which, although negligible around the time of Krakatoa, have become a dominating influence in recent decades.

Volcanic eruptions cool temperatures by emitting particles that scatter sunlight. In contrast, greenhouse gases such as carbon dioxide warm temperatures by trapping sunlight in the atmosphere.

The study appeared in the February 9 issue of Nature.

John Merrill
John Merrill, head of SCD's Mass Storage Systems Group, bids adieu to the last High Performance Parallel Interface switch as it leaves the NCAR Computer Room. SCD decommissioned HiPPI technology at NCAR on January 12. (Photo by Lynda Lester.)

Data storage. As NCAR acquires more powerful supercomputers, it needs larger data repositories. At the beginning of this year, NCAR's Mass Storage System (MSS) held more than 2.5 petabytes—the equivalent of 2.5 billion 500-page paperback novels—with more data pouring in all the time.

To store all this information and ensure that it can be accessed speedily and reliably, SCD has finished phasing out the technology, known as High Performance Parallel Interface, that had supported the storage system for 13 years. A popular technology in the late 1980s to mid-1990s, it was designed for connecting supercomputers and storage devices.

The MSS now uses Fibre Channel and Gigabyte Ethernet technology. Well-suited for connecting storage controllers and drives, these technologies offer data transfer rates of 1 gigabyte per second.

Files can now be transferred three to four times faster than before, although users may not notice a sudden change because the transition has been gradual. In addition, the storage capacity of Fibre Channel–enabled media and tape drives is 3.3 times greater than the devices they replaced. These improvements will allow the MSS to expand yet further into the multi-petabyte range.

For more about the transition.

Weakened hurricanes. One of the mysteries of hurricanes is why the storms sometimes undergo rapid changes in intensity. A recent study by a team of researchers, including MMM's Xiaoyan Zhang and Qingnong Xiao, has yielded important insights into Hurricane Lili's unexpected loss of punch in 2002.

Lili neared the Louisiana coast on October 2 as a Category 4 storm, but it weakened quickly to Category 1 as its maximum sustained winds dropped by 52 miles per hour (84 kilometers per hour) in the 13 hours before landfall. The weakening was not predicted by computer models and it caught forecasters by surprise.

The research team, including scientists from Mississippi State University, gathered data about Lili from a number of satellite instruments that provided different views of the storm. They also used data from dropsondes. To model the storm, they fed information about its surface and upper-level winds, as well as moisture and sea surface and air temperatures, into the NCAR/Penn State University MM5. They used the NCAR Four-Dimensional Variational Analysis system to simulate conditions as the hurricane lost strength.

The simulation indicated that the weakening was partially caused by low-level drier air moving into the west side of the storm. The dry air intrusion, which was not detected at the time, caused Lili's eyewall to start to break down, leading to rapid weakening.

Lili

Lili
Hurricane Lili. These NOAA geostationary operational environmental satellite (GOES) images show the rapid weakening of Hurricane Lili. The image at left shows Hurricane Lili with a clearly defined eye and symmetrical structure in the afternoon of October 2, 2002. By landfall the next morning, the weakening storm has lost its eye and its western winds are less intense.

Snowpack and carbon dioxide. New research indicates that milder temperatures and a reduced snowpack in the Rocky Mountains are slowing the release of carbon dioxide (CO2) from forest soil. The findings raise the prospect that forests may sequester additional CO2 in the wintertime as global temperatures warm, slightly restraining the impact of greenhouse gases on climate change.

Russell Monson of CU and David Lipson of San Diego State University headed the research team, which included Sean Burns (MMM/CU), Andrew Turnipseed (ACD), and Tony Delany (retired from EOL). The scientists used CO2 sensors perched on towers at the CU Niwot Ridge Ameriflux site. They continuously measured CO2 exchanges between the ground and air from 1998 to 2004. The observations showed that the shallower the snowpack, the less CO2 left the ground.

Trees and other plants contribute organic carbon to the soil when they die and decay; the CO2 is then returned to the atmosphere by microbial organisms in the soil. The findings indicate that the microorganisms, which are highly sensitive to temperature change, release more of the gas when there is a deep snowpack that insulates the soil and keeps it relatively warm. In recent decades, however, snowpacks in parts of the Rockies and some other mountain ranges have dropped by 50% to 75%, allowing the soil to get colder.

The study was published in the February 9 issue of Nature.

Vehicle emissions. One of the key provisions in the Clean Air Act requires drivers in heavily polluted urban areas to pass regularly scheduled emissions tests in order to register their vehicles. But a provocative analysis by Asim Zia (ISSE) suggests that drivers are finding ways to avoid this requirement. As a result, the Clean Air Act may be falling short of its potential in cleaning up vehicle emissions.

Focusing on the Atlanta area, Asim posed a basic question: were vehicles that had failed their emissions tests continuing to exceed lawful standards? He extensively analyzed data from an Environmental Protection Agency network of roadside sensors that took 1.5 million observations of motor vehicles from 1997 to 2001, including their license plate numbers and tailpipe emissions. His study found that 58% of the failed vehicles were continuing to exceed the Clean Air Act requirements, while 42% were in compliance.

Asim's conclusion: drivers were using a variety of strategies, such as getting temporary repairs or registering their vehicles outside the metropolitan area, to avoid the sometimes considerable costs required to meet the standards. As a result, emissions of such pollutants as carbon monoxide, hydrocarbons, and nitrogen oxides were not being curbed as successfully as possible.

Turning to Geographic Information Systems (GIS) technology and census data, Asim also determined that people who fit certain profiles, such as males and those with lower incomes, were less likely to be compliant. He is continuing to analyze the data to determine how changing demographics in the Atlanta area could affect future compliance. By using agent-based models (which track individual agents, such as certain types of drivers), he is simulating the emerging patterns of vehicular emissions in Atlanta and other heavily polluted metropolitan areas of the world.

Such research may help policy makers to find ways to boost compliance and better protect air quality

• by David Hosansky and Lynda Lester


In this issue...

Foothills Lab 0: ACD settles into new digs

Staffers give high marks to new Leave Donation Program

Short Takes: An overview of projects throughout the organization

Random Profile: Gina Starr

Roberta Johnson named director of teachers association

Delphi Questions: FL basketball court, phone solicitations

Just One Look


 

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