UCAR Communications


staff notes monthly

November 2002

An overview of projects throughout the organization

As part of the institution’s multidisciplinary Analytical Photonics and Optoelectronics Laboratory (APOL), several divisions are collaborating on the development of a high-precision spectrometer. The goal is to design an instrument that scientists will be able to take into the field for continuous measurements of carbon dioxide isotopic ratios (13CO2/12CO2), thereby allowing researchers to distinguish between oceanic and terrestrial sources of CO2 as well as to characterize the importance of various photosynthetic pathways. At present, scientists have to collect samples in glass flasks and bring them into the lab for analysis—a time-consuming task that limits them to collecting a few samples per week.

NSF is providing a $1.25 million grant for the three-year project to develop the spectrometer, which will incorporate such technologies as diode lasers, fiber lasers, optical fiber amplifiers, and difference frequency generation. Part of the NSF grant will fund a program coordinated by EO to inform high school teachers and students about this project, using it to illustrate the process of scientific inquiry and the development of research instruments. Those involved in the project include ATD’s Dave Carlson and Dirk Richter, ACD’s Alan Fried and Jim Walega, and CGD’s Dave Schimel, as well as scientists at CU, Rice University, and NOAA. For more information about the spectrometer and other APOL projects, see www.apol.ucar.edu.

In 1997, the Taiwan Civil Aeronautics Administration selected RAP and MMM to design, create, and implement the Advanced Operational Aviation Weather System (AOAWS) as part of a technology transfer program between the United States and Taiwan. RAP’s Bill Mahoney, MMM’s Jordan Powers, and their teams worked with the Institute for Information Industry, a nonprofit information technology organization in Taiwan.

This July, AOAWS successfully completed its final site and reliability tests. Now operational, the system is used daily by the Taiwan Civil Aeronautics Administration. It monitors hazardous phenomena (such as clear air turbulence, wind shear, and thunderstorms) and other weather conditions that affect airspace capacity and the safety and efficiency of aviation operations. For more information, see www.rap.ucar.edu/projects/taiwan.

In collaboration with Olusegan Goyea, a first-year SOARS protégé, members of the Atmospheric Radical Studies group in ACD have performed the first tests of a new method to separately detect tropospheric peroxy radicals (HO2 and RO2). Past deployments of the Peroxy Radical Chemical Ionization Mass Spectrometer (PerCIMS) instrument, which consisted of varying the concentrations of gases added to the instrument inlet, have had limited success in measuring HO2-only or combined HO2 and RO2 concentrations.

The new method dilutes the air sample with nitrogen or oxygen, thereby (according to initial studies) effectively separating the radicals. Such research is important for a better understanding of tropospheric ozone because the HO2 and RO2 radicals initiate a chain reaction that leads to ozone formation and ultimately causes smog. ACD’s Chris Cantrell and Gavin Edwards, assisted by Sherry Stephens, are overseeing the research.

Stratocumulus clouds, which form and persist over subtropical ocean waters that are much colder than the local atmosphere, have long been recognized for their significant impact on the radiative balance of Earth, and thus on global climate. For this reason, researchers have focused considerable effort on modeling the evolution of these clouds and parameterizing their processes. One of the key processes is the entrainment rate—the rate of transport of relatively warm and dry air across cloud tops into the marine boundary layer, which determines whether a cloud thickens or thins with time.

In July, Don Lenschow, Ian Faloona, Teresa Campos, Bruce Morley, and other NCAR scientists participated in the second study of the Dynamics and Chemistry of Marine Stratocumulus experiment (DYCOMS-II), using the NSF/NCAR C-130 aircraft for a series of flights west of San Diego to obtain data on entrainment rates that could be compared with model predictions. A detailed analysis of the first flight revealed that the cloud layer was deepening throughout the flight—despite conditions that had been characterized in previous theoretical and modeling studies as conducive to cloud thinning and breakup. Such results indicate that models may overestimate the entrainment rate. More information on DYCOMS-II and initial results can be found at www.atmos.ucla.edu/~bstevens/publications.html.

HAO’s Arturo López Ariste and Roberto Casini have created the first maps of the Sun’s magnetic field associated with solar prominences. The maps are particularly significant because very few measurements of the magnetic field have ever been made—and none in the last 20 years. Prominences form when the solar magnetic field creates stable traps for gases high in the corona. The resulting prominences are made of relatively dense and cool gas (about 10,000 kelvins, or 17,540°F) in the solar corona, which is about 100 times hotter and much less dense than the prominences.

HAO's Arturo López Ariste and Roberto Casini recently created this image of a solar prominence, with its magnetic field measured in gauss. This is the first such image that scientists have created of a prominence. Arturo and Roberto used original data and their own codes, along with HAO instrumentation.

Occasionally, a trap loses its stability and explodes as a coronal mass ejection, hurling material into space and, sometimes, toward our planet. Large CMEs can disrupt satellites, communications networks, power plants, and other systems; smaller ones merely create auroras in Earth’s atmosphere. The coronal eruptions are believed to be caused by a drastic change in the magnetic topology of the prominences and the solar corona around them. For more about the Sun, including CME images, see www.hao.ucar.edu/public/education/slides/slides.html.

CGD’s Aiguo Dai and Kevin Trenberth recently estimated a key part of the global hydrological cycle: the freshwater discharge into the oceans. This provides important data for climate modelers, hydrologists, and oceanographers. The new estimate is based on discharge from the world’s largest 921 rivers, supplemented by estimates from unmonitored regions. By using various data sets, the scientists estimated global continental discharge at about 37,000 cubic kilometers per year (about 8,800 cubic miles, or enough to cover the United States in water 13 feet deep). That amounts to about 7.6% of global precipitation (the estimate excludes about 2,000 km3 per year from Antarctica). They partitioned this discharge into individual oceans at 1-degree resolution (about 65 miles, or 105 km) and tracked it monthly. The results showed that the peak discharge into the Arctic and Pacific Oceans occurs in June, as opposed to May for the Atlantic Ocean and August for the Indian Ocean. Their research has also quantified the effects of delay in runoff due to snowmelt on freshwater discharge and evaluated the continental discharge implied by two recent reanalyses of data: one from the National Centers for Environmental Prediction and NCAR and the other from the European Centre for Medium Range Weather Forecasts.

River flow has important ramifications for global climate because the mix of freshwater and saltwater influences ocean density and, hence, ocean currents and sea surface temperatures. It also is critical to Earth’s hydrological cycle, transporting water from land to ocean, from which most of it returns to land via atmospheric moisture and rain. For more information, see www.cgd.ucar.edu/cas/adai/papers/runoff-paper1.pdf.

Also in this issue...

Space: The never-final frontier

Returning to Center Green


A look back at FL's beginnings

NCAR receives national FAA award

Random Profile: Allen Schanot

Helping Alaskans adjust to climate change

From Bombay to Boulder

Delphi Questions

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