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Winter 2000

Geophysical Turbulence Program gets full-time director

by Carol Rasmussen

Annick Pouquet. (Photo by Carlye Calvin.)

It's "the last outstanding problem of classical physics," as Annick Pouquet points out. Turbulence is getting added attention at NCAR with Pouquet's hiring as the first full-time director of the Geophysical Turbulence Program (GTP).

Turbulence is intrinsic to moving fluids on every scale, from the blood in your veins to the atmosphere. The basic equations needed to calculate a turbulent flow—the Navier-Stokes equations—have been known for more than 150 years (although even today's supercomputers can't calculate fast enough to simulate the full spectrum of atmospheric turbulence). But when it comes to theory, Pouquet says, "We're [still] looking for the concepts. We may not have them yet."

Virtually since NCAR was founded, some scientists have worked on turbulence problems. Because the phenomenon occurs throughout the atmosphere, oceans, and sun and is both observed and modeled, every NCAR division has been involved over the years. In the center's early decades, a Turbulence Club met regularly so researchers in different divisions could share knowledge and brainstorm. The GTP was created in the mid-1980s. The program is housed in NCAR's Advanced Study Program, but it is an NCAR-wide activity that sponsors a summer workshop, seminars throughout the year, and scientific visitors—all on a shoestring budget. Various NCAR staff members, including Jackson Herring (one of the program's founders), Joseph Tribbia, Sasha Madronich, and Peter Gilman, have led GTP over the years. Currently, 36 NCAR scientists are involved.

Pouquet, who came to NCAR this fall from the Observatory of the Cote d'Azur (or OCA, Nice, France), specializes in turbulence coupled with a magnetic field and in problems of intermittency. She intends to continue GTP's visitor appointments and seminar series, increasing both activities as funding permits. The summer workshop, which is in some ways the core of the program, will also continue. Next summer's topic, chosen by consensus of the NCAR scientists involved, is Fronts in Scalar and Vector Fields. Pouquet explains that fronts are "both theoretical concepts and meteorological concepts," and they occur in many geophysical contexts: for example, there can be pollution fronts.

The workshop will take place at NCAR on 27–30 June. It is being organized by Pouquet, Richard Rotunno (NCAR Mesoscale and Microscale Meteorology Division), and Massimo Vergassola (OCA). Like all the GTP workshops, it will attract researchers from a wide range of disciplines. All speakers will be invited, and other interested scientists are welcome to join the audience. As more information becomes available, it will be linked to ASP's Web site.

Over the longer term, one of Pouquet's goals is to continue to bring NCAR up to date on the progress in turbulence research that is taking place worldwide. As an example, she cites the work of Robert Kraichnan (Los Alamos National Laboratory) on isotropic flows. "When we describe a turbulent flow," Pouquet says, "we try to simplify things by calling it homogeneous and isotropic. The idea is that far [distant] from a forcing, a flow becomes isotropic again. This idea has been challenged seriously" in Kraichnan's work. "Is there 'memory' in the flow? If so, it's annoying because you have to account for it. We may have to reformulate what we mean by isotropy."

Pouquet will use the visitor appointments and seminars to help accomplish this goal, and she would also like (if funding permits) to begin a series of smaller, more specialized workshops in which scientists from outside the institution would brief and interact with interested staff on specific developments and problems. In a related effort, NCAR director Tim Killeen has asked Pouquet to smooth the way for cross-divisional exchanges and to identify problems that might be attacked with methods from turbulence research.

Pouquet is also considering how to attract more workers to turbulence research. "It is fascinating as an intellectual endeavor, but the pay is not much compared to the golden boys [in computer science]," she says, echoing a common theme of today's research community. Down the road, she'd like to have one-week lecture series at the graduate level to introduce young scientists to the outstanding problem of turbulence.

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Edited by Carol Rasmussen, carolr@ucar.edu
Prepared for the Web by Jacque Marshall
Last revised: Wed Feb 7 15:34:33 MST 2001