The movies show results from numerical simulations with the EURAD modeling system for an episode in July 1994 with high ozone concentrations over Europe. Presented are the ozone values as simulated by the EURAD model for the lowest layer and for layer 7. The lowest layer has a thickness of about 70 m; layer 7 covers the altitude range from 1300 m to 1800 m.

The ozone concentrations shown are from a typical summer episode, which occurred over Central Europe in July 1994. This episode is characterized by high ozone concentrations of more than 100 ppbv over large areas in Europe. Four movies are currently available which illustrates the dynamic patterns of the ozone distribution over Europe during that episode:

1. near-surface ozone concentration for the whole of Europe

2. ozone concentration at an altitude of about 1500 m (residual layer) for the whole of Europe

3. near-surface ozone concentration for Central Europe (zooming/nesting option)

4. ozone concentration at an altitude of about 1500 m (residual layer) for Central Europe (zooming/nesting option)

The near-surface ozone concentrations displayed in the first movie shows the typical patterns which develop during an ozone-episode. Ozone is formed during the day within the atmospheric boundary layer from nitrogen oxides and hydrocarbon emissions, mainly due to anthropogenic sources (traffic, industry). During the night ozone is converted to NO2, in particular in highly industrialized areas for example the western part of Germany and the Benelux states. In the beginning of the episode (July 21 - July 23) ozone is transported with the prevailing easterly wind from the main emission regions along the western and northern coast of France and Spain towards the North Atlantic. During the episode, ozone values increase and large amounts of ozone are transported towards the North Sea during July 24 and 26 and to Scandinavia in the days from July 27 - July 30.

In the second movie the ozone patterns for an altitude of about 1500 m are displayed, again for the whole of Europe. Ozone which is formed within the well-mixed convective atmospheric boundary layer during the day remains in the upper part of the boundary layer during the night. This leads to the formation of the so-called residual layer, where ozone which has been generated during the days before can remain for several days and might be transported over large distances during the night. The formation of the residual layer is due to the strongly decreased turbulent mixing which prevent the contact of ozone with the near-surface layers during the night. Losses of ozone can only occurr in the near-surface layers by dry deposition at the ground and due to conversion to NO2 near the emission sources which are also located mainly near the surface. Both processes are hampered during the night due to the strongly decreased turbulent mixing. During the day ozone from the residual layer can be transported to the near-surface layers by turbulent mixing and contributes to the increase of ozone in the morning hours.

The movies (3)and(4) again show the ozone concentration for the near-surface layer and layer 7 (about 1500 m altitude) but with a better resolution for Central Europe. The plumes of major cities can be better identified on that scale. In particular the plume of Berlin can be seen. During the first days of the episode (July 21 - July 25) the ozone plume of Berlin is usually transported towards Northwest. The situation in much more complex during the time from July 26 - July 30 with changing wind directions. In particular during July 29 the ozone plume from Berlin moves northward towards the Baltic Sea and Southern Sweden (simulation results for layer 7).

As an extension of the model simulations presented here an application to investigate chemical and dynamical processes in the urban plume of Berlin with increased horizontal resolution is currently underway.

The numerical simulations for this episode has been carried out within the research project AAMOSS which is financially supported by the BMBF of the Federal Republic of Germany within the framework of the Tropospheric Research Program (TFS).

Emission data has been provided by EMEP (E. Berge) and the IER, University of Stuttgart (R. Friedrich, B. Wickert). Landuse data provided by Dr. G. Smiatek, IfU, Garmisch--Partenkirchen, to the data bank of the TFS--LT1 managed at the BTU Cottbus (Lehrstuhl für Umweltmeteorologie) have been used. Meteorological data has been provided by ECMWF and the DWD. The preparation of meteorological input data for MM5 has been supported by Prof. P. Speth, Ilona Stiefelhagen and Birdie Roeben, University of Cologne.

The numerical simulations have been supported by the Research Centre Jülich (ICG2, ICG3 and ZAM) and the RRZK of the University of Cologne. In particular the support by H. Geiss from ICG2 is gratefully acknowledged.

EURAD is financially supported by the Ministry for Education, Science, Research and Technology (BMBF) within the Tropospheric Research Program (TFS), the Ministry of Science and Research (MWF) of the Federal State Nordrhein-- Westfalen, the FORD Research Centre Aachen (FFA) and the European Commission, DG XII.