Sandia LabNews

Unique instrument completes climate study comparison


Lidar automatically profiles water vapor in atmosphere at 120-foot increments

Imagine being able to watch moist air gather and dissipate in Paradise Hills from Albuquerque,or from Livermore to Dublin, through night and day, for more than a decade.Climate scientists are receiving a heady long-range data stream from the lower atmosphere thanks to a unique instrument created by Sandia scientists and installed at a DOE weather research station in Oklahoma. The device, recently rigorously compared with other weather research instruments, measures water vapor up to the upper edge of the troposphere, some eight miles above ground. Since humidity traps the sun’s warmth and shifts over time, this understanding will assist predictions of the greenhouse effect and global warming. “Water vapor is the primary green-house gas,” explains John Goldsmith, Manager of Combustion Chemistry Dept. 8353, who counts the time he spent developing this instrument as among the most satisfying in his 20 years at Sandia.

A laser spectroscopist by training, John had created combustion diagnostic devices using similar technology prior to this project, installed in 1995 after a preceding Sandia/NASA collaboration that focused on developing the necessary technology.

"LAB IN A BOX”— The moisture-monitoring lidar system resides in Oklahomain a re-fitted cargo container, customized with heating, cooling, power, and aninstrument table so the sensor can operate automatically around the clock.

Neat research opportunities ’

The instrument identifies water vapor by pulsing laser light for billionths of a second, then recording the light that is scattered back, some of it slightly shifted in wavelength by the molecules of water and nitrogen in the atmosphere. This technique, called Raman lidar, “opened up a lot of neat research opportunities,” says instrument mentor Tim Tooman (8120), who estimates he’s spent seven months at the Oklahoma site over the last five years. “It’s a very useful thing.”

For instance, the surface of the moon was mapped with a back scatter lidar by NASA’s Clementine spacecraft.The lidar system at the Oklahoma site actually pro-files the atmosphere, bracketing readings every 120feet (as if someone could climb a ladder with rungs120 feet apart and record water vapor at each layer). Being able to reach the upper levels of the troposphere is important, because this is where sunlight first encounters climatologically significant quantities of atmospheric water.Aside from being able to provide valuable data, the instrument has also been subject to three studies that compared water vapor measurement techniques. “At the moment,” says Tim, “we’ve taken essentially every important, field able instrument that measures water vapor and compared them to each other.”Tim and John each spent a week in Oklahoma in December during the last phase of the third study, along with researchers who sup-ported the other instruments and met daily for discussion of scientific issues.

In this phase, two more lidars were used. One was taken aloft on the NASA DC-8 jet to study water vapor above and below the aircraft, which was piloted in a column of airspace above the site at night (when sunlight does not reduce the maximum altitude that can be measured by the Raman lidar). John, a pilot,enjoyed coming along in the cockpit jump seat.

Multiple simultaneous measurements

The objective was to have the instruments all measuring the same atmosphere at the same time, Tim said, since every instrument has measurement errors and intercomparisons help show how accurate each is.“In a sense,” he says, “we’re the one to beat.

”The lidar, housed in a revamped cargo container,has been optimized to now operate continuously more than 90 percent of the time and is being improved even further. For instance, in this rural setting, every day or so the voltage would falter for a few thousandths of a second, which used to cause the laser to shut off until power-conditioning units were added.John wrote the software that runs the instrument and is helping improve software that analyzes the data. Measurements obtained during the fall Intensive Observation Period will be evaluated over the next couple of years, and DOE has extended the initial 10-year Atmospheric Radiative Monitoring project another 10 years due to the promise and complexity of the overall research. After an interval leading a team on another project, John was excited to get back involved with the lidar and pleased with the way the unique instrument operates itself. Says Tim,“You’d just come and watch it run.”

Dec’s diesel research paper earns SAE honor

Society of Automotive Engineers announces award

John Dec (8362) essentially rewrote text-books when his diesel engine studies revealed a new conceptual model for how diesel combustion occurs. Now a research paper that expands on that model and points to promising directions for reducing soot emissions has received a merit award from the Society of Automotive Engineers (SAE)for making an original contribution to the subject of diesel combustion. John and his co-authors received one of14 Arch T. Colwell merit awards out of more than 2,160 papers published for SAE meetings in 1999, and will receive a certificate at an honors convocation March 6 in Detroit.John’s paper was co-authored by Cummins Engine Co. colleagues Patrick Flynn, Russell Durrett, Gary Hunter, Axel zurLoye, and O. C. Akinyemi, and Charles West-brook, a chemical kinetics modeler at Lawrence Livermore National Laboratory. It is titled, “Diesel Combustion: An Integrated View Combining Laser Diagnostics, Chemical Kinetics, and Empirical Validation.”The paper combines John’s conceptual model of a reacting diesel fuel jet with West-brook’s chemical-kinetics models to show how the soot-formation zone stabilizes. It then goes on to show how, in this combustion environment, adding oxygenates to the fuel reduces soot formation. Their results explain the main mechanism for the soot reduction that has generally been observed with oxygenated fuels. They are also in very good agreement with experimental data in the literature about the amount of oxygenate required to eliminate soot formation. John says more development of this approach is needed before any commercial application,but the work indicates what directions to take.Selected over a two-year period by are view committee, from a pool of papers provided by a prescreening process, the paper was presented at the SAE International Congress and Exposition in March 1999. In addition to the contributions of co-authors, John says the paper draws on the work of Dennis Siebers (8362), whose research has lead to the development of a scaling law for diesel jet penetration and the rate of air entrainment.This is the ninth recognition John has received from the SAE, including fellowship in the society, two other awards for outstanding papers, and five awards for presentations.The latest presentation award, announced last month, is an “Excellence in Oral Presentation” award for the March 2000 presentation of his SAE paper entitled, “The Effects of Injection Timing and Diluent Addition on Late-Combustion Soot Burnout in a DI Engine Based on Simultaneous Imaging of OH and Soot.”

New fiber-optic classified video system recognized at Pantex plant site

A team of Sandia/Californians and the Pantex TriLab Sandia Office manager were recognized by Mason & Hanger recently for their efforts in developing and fielding a new fiber-optic classified video system. The system is a product of Sandia’s recent efforts to provide systems engineering solutions in response to Pantex plant needs. It was developed because of the need for close monitoring of critical classified operations under potentially hazardous conditions. According to Pantex Deputy General Manager Jim Angelo, “The success of this demonstration was exceptionally noteworthy in that it reduced the number of required visitors [in the operations bay], improved the visual access to the[W88 DOE readiness assessment/nuclear explosive safety study], and provided a playback capability. As a result, the quality of readiness reviews in the future will be greatly enhanced.” Pantex is currently evaluating the use of this system forW56 war reserve activities. The concept for the secure video system, dubbed COViS, for Classified Operations Video System, was researched and managed by Bill Wilson (2250) and Sandia TriLab Office manager John Duncan (2252), who also coordinated the safety approval process. Robert Kinzel (8415, formerly 2253) was responsible for technical design,fabrication, and personnel training for the portable system. Additional management over-sight was provided by Anton West (2253). All four team members were awarded Individual Performance Awards by Mason & Hangar in recognition of their “personal commitment, dedication, and outstanding performance.”