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Summer 2002

A Boulder-Reno team puts students and instruments together

by Bob Henson

Late last winter, NCAR’s Atmospheric Technology Division brought two of its integrated sounding system (ISS) units to the windswept desert just downwind of the Sierra Nevada. The deployment was a field project and a learning exercise rolled into one. Students in a graduate instrumentation class taught by John Hallett (Desert Research Institute and the University of Nevada in Reno) launched radiosondes and explored the use of other sensors from ATD and DRI. The scientific motive was to analyze the inversions that cloak the Reno area each winter, as relatively mild Pacific air flows over stagnant cooler air near the surface.
Participants in the hands-on DRI instrumentation class include (left to right) Mariana Potcoava, Julide Koracin, Lupita Paredes-Miranda (holding a radiosonde), and Dorothea Ivanova. (Photo courtesy Stephen Cohn.)

The 17 students, mostly doctoral, mulled over weather situations as a group and played an active role in the data gathering, says NCAR scientist Stephen Cohn, who helped in planning and teaching the course. "They helped decide when we had our intensive observing periods, when and how to launch balloons—they were making real decisions in an operational setting." Cohn delivered several talks to the class on the ISS and its application in the Reno area.

As atmospheric sensors and the resulting data sets grow in complexity, it’s more important than ever for graduate students—even the most cloistered of number-crunchers—to get their hands dirty in the real world of instrumentation, according to Hallett, a cloud physicist. "Without some basic understanding of the way instruments function and the way they’ve evolved, I think students won’t really appreciate how to evaluate the measurements they’re working with," he says. In three previous installments of his course over the last 13 years, Hallett has made use of a single ISS unit, as well as the former NSF/NCAR Electra aircraft and the CSU-CHILL radar managed by Colorado State University.

Data analysis was a major part of the course experience. Some of Hallett’s students compared data from the radiosondes launched each day by the National Weather Service to data from the ISS sondes, which were deployed from a site just east of Reno about 45 seconds earlier. (The head start compensated for a lower launch altitude.) A second ISS unit, sans sondes, was situated in the Washoe Valley, about 40 kilometers south of town. Both sites are prone to strong inversions, sometimes in multiple layers. The inversions can erode from below (through daytime heating) or from above (through downslope

wind from the nearby ridge). While interpreting the ISS data, the students also pondered how models and other tools might help pin down inversions’ effect on local weather and air pollution and the timing of an inversion’s demise.

The Reno project introduced a new ISS component, a sodar (sonic-based wind profiler). Though the sodar only measures winds to a height of about 350 meters, it fills in a key data gap for the ISS wind profiler. Closer to the ground, readings from a 10-meter, instrument-studded ISS tower were compared with those from a slightly shorter tower from DRI.

In his lectures, Cohn used the ISS to show how even the most sophisticated sensors have their foibles (a coating of snow can mislead the ISS radiation sensor, for instance), and he explained the quality-control techniques used by ATD to ferret out as many problems as possible. "Many of these students haven’t yet settled into a specific research area. We expect that some of them will be more interested in atmospheric measurement because of their exposure to the ISS," says Cohn.

Even those students who never launch another balloon may come away with a deeper appreciation for how data are gathered, says Hallett, whose first encounter with weather sensors occurred some 50 years ago, during his undergraduate days at the University of Bristol (England). Hallett’s early experience as a lecturer at Imperial College (London) convinced him that "teaching instrumentation—and more to the point, demonstrating instrumentation—was absolutely a key part of the education of anybody going into atmospheric science." Since arriving at DRI in 1967, Hallett has offered regular instrumentation courses.

In recent years, ATD staff have used the ISS to support combined research and educational projects with faculty members from the Universities of Michigan and Virginia. The NSF Observing Facilities Advisory Panel, which reviews requests for ATD instruments twice yearly, welcomes requests for educational use of ATD systems. A guide to the request process and ATD’s current deployment schedule can be found on the Web site below. If you have any pre-request questions, contact project specialist Brigitte Baeuerle, 303-497-2061, baeuerle@ucar.edu.

NCAR technician Lou Verstraete (right) demonstrates radiosonde launch techniques to students Tomasz Sikora (left) and Narendra Adhikari. (Photo courtesy John Hallett.)

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Edited by Bob Henson, bhenson@ucar.edu
Prepared for the Web by Carlye Calvin
Last revised: Tues June11 17:05:07 MDT 2002