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Summer 2001

Interactions tropical and scientific mark 2001 ASP colloquium

by Bob Henson

Andrew Moore (left) and Peter Webster. (Photo by Carlye Calvin).

In mid-July, 25 young scientists gathered a mile above sea level in Boulder to learn about ocean-atmosphere interactions in the tropics. The occasion was the 35th summer colloquium offered by NCAR's Advanced Study Program. Each year ASP assembles an all-star group of lecturers to spend two weeks with graduate students and recent Ph.D.s who are hunting for research topics and looking for knowledge that's a step or two ahead of the textbooks.

"It's the first time in 29 years the tropics were explored in this colloquium," says Peter Webster (University of Colorado), who coordinated the 2001 program with CU colleague Andrew Moore. As a green graduate student, Webster attended the last tropically themed colloquium in 1972. He's amazed at how much has changed.

Some topics of recent ASP colloquia

2000: Dynamics of Decadal to Centennial Climate Variability
1999: Ice Formation in the Atmosphere
1998: Hurricanes at Landfall
1997: A Systems Approach to El Niño-Southern Oscillation (ENSO): Oceanic, Atmospheric, Societal, Environmental, and Policy Perspectives
1996: Terrestrial Ecosystems and the Atmosphere
1995: The Planetary Boundary Layer and Its Parameterization
1994: Current Trends in Solar and Astrophysical Magnetohydrodynamics
1993: Clouds and Climate
1992: Observational Techniques in Atmospheric Science
1991: Research Problems in Atmospheric Chemistry
1990: Mesoscale Data Assimilation

This year's presenters

Grant Branstator (NCAR)
Mark Cane (Lamont-Doherty Earth Observatory, Columbia University)
Judith Curry (University of Colorado)
Chris Fairall (NOAA)
Peter Gent (NCAR)
William Gray (Colorado State University)
Weiqing Han (CU)
John Hart (CU)
Greg Holland (Australia, BMRC)
James Holton (University of Washington)
Robert Houze (UW)
George Kiladis (NOAA)
Ben Kirtman (Center for Ocean-Land-Atmosphere Studies)
Richard Kleeman (LDEO)
Tiruvalam Krishnamurti (Florida State University)
Julian McCreary, Jr. (University of Hawaii)
Gerald Meehl (NCAR)
Peter Molnar (CU)
Michael Montgomery (CSU)
Dennis Moore (NOAA)
Tim Palmer (European Centre for Medium-Range Weather Forecasts)
Robert Tomas (CU)
Peter Webster (CU)
Chidong Zhang (University of Miami)

"In discussing tropical meteorology back in 1972, the ocean was essentially not mentioned at all. It was considered to have certain intrinsic characteristics that influenced the atmosphere, but there was no dynamic [ocean-atmosphere] consideration," says Webster. "The concept of ENSO [El Niño/Southern Oscillation] had only just emerged." Jacob Bjerknes had written a pair of landmark papers in the mid-1960s on ocean-atmosphere links in the tropics, but the linkages weren't yet accepted as critical. Only a few months after the colloquium, the 1972–73 El Niño arrived, and a new topic of inquiry was born.

Much of the information at this year's colloquium hasn't yet made it into formal curricula, says Moore. Few schools have enough interested graduate students for a full course on tropical meteorology, and "most of the standard textbooks are a good 10 or 15 years old. I think we've made significant progress since then." For example, vast gaps in data and understanding have been filled in by the Tropical Ocean and Global Atmosphere buoys, stationed across the tropical Pacific since the 1980s, as well as by TOGA's Coupled Ocean-Atmosphere Response Experiment, held in 1992–93. "This is a good opportunity to put together a more comprehensive text, especially with regard to El Niño," says Moore, who plans to write a book with Webster and CU colleague Judith Curry. "The 1997–98 event confirmed a lot of theoretical ideas that were floating around out there for a long time."

Each day of the colloquium featured 90 minutes of roundtable discussion, giving students and lecturers plenty of time to share ideas. The first week provided a basic grounding in tropical theory and observation, including talks on tropical weather and circulation by T. Krishnamurti (Florida State University), hurricane genesis and structure by Michael Montgomery (Colorado State University), and coupled ocean-atmosphere dynamics by Julian McCreary (University of Hawaii) and Richard Kleeman (New York University).

In the second week, presenters delved into the Pacific–North America pattern (a recurrent mode of atmospheric circulation) and several other cyclic phenomena. NCAR's Roland Madden discussed the 40-to-50-day cycle in Pacific tropical convection that he codiscovered in the 1970s. The eastward-moving clusters of wind and thunderstorms referred to as the Madden-Julian Oscillation (MJO) have since been identified as a possible trigger for El Niño events. Most of the colloquium's final two days were devoted to predictability, including the Asian monsoon, ENSO, tropical cyclones, and the tropics in general on time scales from days to decades.

Moore is especially interested in the MJO-ENSO link. "The big issue right now is how much of ENSO can be determined by the initial conditions—the current state of the ocean—and how much is determined by variability in the atmosphere. Prior to the 1997–98 El Niño, there were several large MJO events that produced a sizable response in the oceans. The question is, would the El Niño have occurred if the MJO hadn't produced those westerly wind bursts, or would it have been half the size it was?" To see if ensemble modeling can provide some answers, Moore and Webster are working closely with the European Centre for Medium-Range Weather Forecasts. The ECMWF is now producing ensemble forecasts regularly for the tropical Pacific.

Much like Webster, it's likely that some of the leaders 20 years from now in tropical ocean-atmosphere research will have emerged from this summer's colloquium. "We like to think the students we get are the cream of the crop," says ASP coordinator Judy Miller, who took over administration of the colloquium this year after assisting for a number of years. The acceptance rate for applicants varies, says Miller, but in recent years "almost all the applicants have been on target. Their interest is genuine and the colloquium truly advances their studies." As for the presenters, "a lot of them get a kick out of mingling with the students, and I think they really enjoy getting young people interested in their areas of research." If you have a topic that might be suitable for a future colloquium, Miller and ASP director William (Al) Cooper welcome your input.

On the Web:
Notes from the ASP colloquium

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Edited by Bob Henson, bhenson@ucar.edu
Prepared for the Web by Jacque Marshall
Last revised: Wed Aug 8 17:05:07 MDT 2001