December 15, 2005
IMAGe workshops study new approaches to atmosphere and climate modeling
High interest in Theme-of-the-Year program leads to addition of fourth workshop
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| Robert Fovell of the University of California at Los Angeles illustrates a point in his presentation on atmospheric gravity waves at the second IMAGe Theme-of-the-Year workshop, held at NCAR from October 31 to November 4, 2005. Workshop II photos | |
Applied mathematics, cloud superclusters, hurricanes, convection, numerical models—they all come together in a series of four interdisciplinary workshops on new mathematical strategies for atmosphere and climate modeling being hosted in Boulder by NCAR’s Computational and Information Systems Laboratory (CISL) in 2005 and 2006.
Sponsored by CISL’s Institute for Mathematics Applied to Geosciences (IMAGe), the workshops are being led by Andrew Majda and Joseph Tribbia. Majda is the Samuel Morse Professor of Arts and Sciences at New York University’s Courant Institute of Mathematical Sciences. Tribbia is a senior scientist in NCAR’s Climate and Global Dynamics Division and a member of IMAGe’s Data Assimilation and Research Section.
The year-long workshop series focuses on the use of mathematical methods to describe interactions of geophysical processes that occur across different spatial and temporal scales. Each five-day workshop includes three days of tutorial and two days of technical presentations, with plenty of time for discussion and interaction.
One goal of the workshops is to establish a two-way communication between the university mathematics community and the scientific community at NCAR, focusing on specific areas of research that will benefit from intense collaboration. Another goal is to expose Ph.D. students, post docs, and junior faculty in applied mathematics and statistics to the scientific issues and principles in modeling the atmosphere.
“The workshop model is to mix tutorials with technical talks,” says Douglas Nychka, director of IMAGe. “What makes it work is that Andy and the other senior scientists at the presentations are careful about making sure terms are defined and gaps that inadvertently pop up in the talks are elaborated on. Andy also does a good job in encouraging students to ask questions, often a scary proposition for a young scientist.”
The first two workshops, held in Fall 2005, generated a high level of interest. Registrations for the third workshop (February 27–March 3, 2006) and the fourth workshop (May 15–19, 2006) are now being taken.
Funding is available to support workshop attendance, with special emphasis given to graduate students and other young researchers. Those who are not working directly on workshop topics but are interested in the program are also encouraged to apply, as are members of underrepresented groups. For more information, contact Liz Rothney (303-497-1351, rothney@ucar.edu).
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| Andrew Majda of New York University’s Courant Institute, co-director of the IMAGe Theme-of-the-Year program, encourages discussion at the first workshop, held at NCAR in September 2005. Workshop I photos | |
Strategies for multiscale and stochastic modeling
The workshop program is based on the IMAGe Theme-of-the-Year, “Emerging Mathematical Strategies for Multiscale and Stochastic Modeling of the Atmosphere and Climate.” This theme addresses a notoriously difficult challenge: how to resolve the interaction between geophysical processes that occur on different scales.
Many important processes occur at scales that are too fine for the broad-scale grids of climate models to resolve. However, subgrid processes, which include convection and cloud formation, have significant impacts on the circulation of the atmosphere. Resolving the interactions between scales will lead to improved understanding of climate and improved weather forecasting.
“The theme of these workshops is multiscale mathematics,” says Tribbia. “Multiscale means that rather than having a uniform modeling environment where you’re simulating the atmosphere at, say, a global scale (which is what we’re trying to do in climate modeling) or on a convective scale (which is going on in mesoscale simulation and weather prediction), you get the physics and dynamics of both scales to talk to each other mathematically.”
A number of research efforts at NCAR and in the external mathematics community make it exciting to be talking about this theme now, Tribbia says. To cite one example, scientists in NCAR’s Earth and Sun Systems Laboratory (ESSL) are working on linkages between scales in atmospheric modeling.
Nychka explains the rationale behind choosing this particular Theme-of-the-Year. “Andy leads an active group at Courant, and he has innovative ideas in terms of dealing with subgrid-scale processes—atmospheric processes not resolved by a model but that need to be accounted for because of the model’s behavior,” he notes. “We wanted to reinforce the synergy between his work and the kind of physical modeling happening with NCAR scientists.”
“Multiscale modeling is just one instance in which NCAR could benefit by receiving guidance from the mathematics community about how to best go about solving these problems,” Tribbia adds.
Another instance is in the application of stochastic modeling techniques, which call on a large set of data about the past in order to find patterns and calculate probabilities about the future. Because today’s computers are not yet powerful enough to completely resolve processes at small scales, scientists use a stochastic method called parameterization to approximate them. Convection is one process that is normally parameterized.
“In simple terms, convection transfers heat from the surface to the upper atmosphere,” says Doug. “It happens at the local or regional scale—thunderstorms are an extreme example—but affects the overall way heat is distributed in the atmosphere. So this brings us back to multiscale processes. In planning these workshops, Andy and Joe felt that some presentations dealing with convection were central to the program.”
The third workshop in the Theme-of-the-Year series, “Stochastic and Statistical Parameterization of Unresolved Features in the Atmosphere and Upper Ocean,” will examine mathematical methods to better represent subgrid-scale atmospheric processes such as convection.
The fourth workshop, “Multiscale Processes for Low-Frequency Variability, Climate, and Climate Change Response,” will discuss topics such as atmospheric variability and seasonal cycles, coupled general-circulation models, and climate observational data.
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| Joseph Tribbia (front row) and colleagues ponder mathematical theory at the first IMAGe Theme-of-the-Year Workshop. Tribbia, a senior scientist in NCAR's Climate and Global Dynamics Division, is working with NYU’s Andrew Majda to organize the workshop series. Workshop I photos | Mitchell Montcrieff, head of the Cloud Systems Group in NCAR’s Mesoscale and Microscale Meteorology Division, delivers a presentation on convection at the second IMAGE Theme-of-the-Year Workshop. Workshop II photos |
Multidisciplinary collaborations
One hope of workshop organizers is to nurture multidisciplinary collaborations between researchers at NCAR and scientists and applied mathematicians at the Courant Institute, including faculty in Courant's Climate, Atmosphere, and Ocean Sciences Department.
“Part of the reason Andy agreed to co-direct these workshops is that he had productive connections with NCAR in the past,” says Nychka. “The program is a way to strengthen these connections substantially, as well as to develop connections between Andy’s students and NCAR scientists. Andy’s role in participating and steering the workshops has been delightful. We appreciate the time he has invested in this program ”
“There’s been a lot of good communication,” Tribbia agrees. “The Theme-of-the-Year has been a success so far. The first two workshops were well attended, and registration is coming in for the third. The test will be if the collaborations built up within the year will extend longer than this point in time. The real scientific applications will be in the next couple of years down the road.”
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The workshop series also highlights interactions between IMAGe and the Scientific Computing Division (SCD), which merged in Fall 2004 to form CISL. Scientists in IMAGe and SCD are working together closely on many of the research topics being featured in the Theme-of-the-Year workshops, creating numerical tools and developing mathematical models for describing geophysical processes.
CISL is part of the National Center for Atmospheric Research, which is operated by the University Corporation for Atmospheric Research under the primary sponsorship of the National Science Foundation.—Lynda Lester
