February 28, 2007
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FROM VOLUME 12, NUMBER 2, FEBRUARY 1999
EUROPEAN TRACER EXPERIMENT
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
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
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.
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