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FROM VOLUME 12, NUMBER 2, FEBRUARY 1999

JOURNAL ARTICLES...
EUROPEAN TRACER EXPERIMENT

Item #d99feb22

Atmospheric Environment 32 (24), 4089-4378 (1998).

This special issue is devoted to ETEX, the European Tracer Experiment in which perfluorocarbon tracers were released from Monterfil, Brittany, France, in October and November 1994 and tracked for 72 hours across 17 European countries by a network of 168 ground stations. Upper-air measurements were also made by three aircraft. In October, a westerly air flow carried the plume to the northeast across Europe. In November, the plume went east. In the course of the two releases, the tracer clouds were sampled as far away as Poland, Sweden, and Bulgaria. The experiment recorded tracer concentrations at ground level and in the upper air, routine and special meteorological conditions, and the trajectories of constant-altitude balloons.

At the time of release, atmospheric modelers from 20 countries entered the conditions of the release into their models and predicted the long-term dispersion within a few hours. Their predictions were updated during the ensuing days as the experiment progressed and more meteorological data became available. The model results were compared with observations. In the first release, the majority of predictions were good. For the second release, the results from all of the models were unsatisfactory. The information gathered by the ground stations and other components of the experiment was compiled in a database that is available on the Internet at http://www.ei.jrc.it/etex as a unique tool for model developers. The major conclusions drawn from the experiment are:

• No distinction could be made between the performance of Lagrangian and Eulerian models.
• Model performance improves with met-data resolution.
• Theories about the structure and turbulence of the atmospheric boundary layer under complex conditions are still a long way from being useful in predictive modeling.
• Massive vertical transport in clouds (deep convection) cannot be neglected in dispersion models.
• Dispersion predictions based on meteorological observations are somewhat but not significantly different from those based on weather forecasts.

Papers in the special issue of Atmospheric Environment detail the methods used, the data gathered, analyses of the data, and validation attempts of many dispersion models.