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April 1998

Science Briefing

UCAR and NCAR will join forces with 12 weather services and 25 research institutes in Europe and Canada--as well as NOAA, the Naval Research Laboratory, and eight U.S. universities--for a major field program in the Alps next year. On 23-26 February, UCAR sponsored an international planning meeting for MAP, the Mesoscale Alpine Experiment, at the Regal Harvest House. On hand were about 25 European and 40 U.S. scientists, including several from NCAR. The meeting was led by Joach Kuettner, who holds the UCAR Distinguished Chair for Atmospheric Sciences and International Research.

Joach Kuettner

MAP will use the densely instrumented Alps to explore the three-dimensional effects of complex topography. MAP's goals are to study the mechanisms behind severe mountain-induced flooding and to examine the dynamics of other mountain-related phenomena, including some that have never been systematically studied and some only recently discovered.

A unique feature of MAP is the two-year modeling phase, now under way, that will lead into the field phase (August-November 1999). The modeling will help gauge the predictability of phenomena to be studied and will help set the observing strategy.

"The advance of operational mesoscale models has led us into a new situation," says Joach. "The resolution of the latest models exceeds that of the observing network. Instead of trying to understand and model features observed in the atmosphere, we are now faced with the opposite problem: verifying and exploring features that are deduced from the models."

For instance, Swiss models have recently indicated that the Alps generate potential vorticity (PV) banners. Appearing in the models as alternating bands, these circulation features extend downstream up to 600 miles (1,000 kilometers) from major alpine peaks. PV banners may be involved in the formation of cyclones to the lee of the mountains. MAP planners hope to use airborne Doppler or flight-level wind data from aircraft to find PV banners and compare them to model predictions.

The alternating dark and light bands in the above graphic are banners of potential vorticity (PV), a measure of circulation in the atmosphere. The banners, discovered several years ago by Swiss modelers, are produced in this model depiction by northerly winds passing over the Alps (outlined in bright white). MAP hopes to verify the presence of PV banners in the Alps through observations in the fall of 1999. (Illustration courtesy MAP.)

Dubbed the "Watertower of Europe," the Alps feed the continent's major rivers (the Rhine, Danube, Rhone, and Po) and produce dramatic, sometimes catastrophic, floods. The region's 150-year meteorological data set supports the choice of autumn as a prime time to observe major rainfall and mountain-wave events. MAP will examine the "breaking" of high-altitude mountain waves--which can cause severe turbulence--and study airflow through passes, which Joach calls "a seriously neglected area" of research.

A big drawing card for the Alps is its instrument network, among the world's most dense. There are several hundred automated weather stations, over 6,000 rain gauges, and about 20 overlapping radars (primarily Doppler) in place. MAP will draw on these systems for a 13-month general observing phase starting this October, which will lead into the actual field phase. Pending approval, NCAR will bring its S-Pol radar and the NSF/NCAR Electra aircraft (and, if available, the WB-57 jet) to the field phase. Also in the plans are NOAA's P-3 aircraft and Doppler on Wheels.

MAP will serve as a homecoming for Joach. He explored mountain waves in Europe and the United States during the 1930s and 1950s as a researcher and a pilot, and set an unofficial world record for glider altitude (around 43,000 feet, or 13,000 meters). In 1982, Joach headed the Alpine Mesoscale Experiment (ALPEX), part of the Global Atmospheric Research Program. "ALPEX is the true forerunner of MAP," says Joach. He adds, "The preparations for this project and the cooperation among scientists on both sides of the Atlantic are among the best I have encountered in my life. It will be a fascinating experience."

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Edited by Bob Henson, bhenson@ucar.edu

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