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  Hungarian Meteorological Service  founded: 1870
Research and development | Numerical Weather Prediction  | Analysis of the Atmospheric Environment | 
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Following the path of the polluting particles - trajectory calculations with the FLEXTRA 3.0 trajectory model

(Krisztina Labancz)

Calculation of the pathway of polluting materials is an essential task in the case of a nuclear or chemical industrial accident. In 2004, in the framework of a co-operation with the National Nuclear Energy Agency, we developed a programme system for trajectory calculations. For this purpose we downloaded and adopted the FLEXTRA Trajectory Model Version 3.0 from the web site of the University of Munich, Germany. The model is the basic modul of our system. In addition to the traditionally used isobaric trajectories, this model calculates 5 types of backward and forward trajectories: three-dimensional, iso-eta, mixing layer, isobaric and isentropic trajectories. The input meteorological fields of the FLEXTRA model are calculated from the three-dimensional analysis fields of the ALADIN/HU and ECMWF numerical weather prediction models.

Some basic trajectories are calculated by our programme on a daily routine basis. Any other trajectories (starting at locations and times as specified by the user) can be calculated and graphycally reproduced by the HAWK meteorological visualization system, which was developed at the Hungarian Meteorological Service. The HAWK system can be used on an interactive way: the user can define the type and the time-lenght of the trajectory, the receptor or source coordinates of the air parcels, and the source of the input meteorological fields.

Forward and backward trajectories,
14.11.2004, 15:00 UTC, Budapest


Boundary layer and isobaric trajectories,
14.11.2004, 15:00 UTC, Budapest

Isobaric and isentropic trajectories,
14.11.2004, 15:00 UTC, Budapest

There are some other advanced options for making more detailed analysis: the FLEXTRA model calculates ensemble trajectories, trajectories along the flight leg of an aircraft and the uncertainty of the trajectories. At the end of this work, a detailed validation of the programme was made, where the role of the different types of trajectories was analysed using a real weather situation.
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