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Last year we adopted a second-generation local-scale dispersion model, called AERMOD, at the Hungarian Meteorological Service in order to make better regulatory modelling for concentration calculations than with our old model TRANSMISSION 1.0. In this article the main features of the AERMOD modelling system are mentioned. We summarize our experiences in connection with the model. We also examined the sensitivity of the model to the meteorological and surface parameters, used by this model.

The advection scheme TRAP (from TRAPezium) was elaborated for building in the Bulgarian air pollution dispersion model EMAP, which is a 3D PC-orientated Eulerian multi-layer model. The TRAP scheme is a Bott-type one and possesses all good properties of this scheme: it is explicit, positive definite, conservative with limited numerical dispersion and good transport ability being at the same time much faster than the Bott scheme. Instead of integrating the polynomial fit over the neighboring grid values as in the Bott scheme, the flux area in the TRAP scheme is supposed trapezoidal and its value is determined as a product of the Courant number and a single value of the polynomial referring to the middle of the passed distance. In this paper some new and faster schemes built on the base of the TRAP scheme are described and tested. They are obtained by optimizing Bott’s “normalization” procedure. The performance quality is determined by exploiting the rotational test: an instantaneous release is rotated in a 101×101 grid point field. A set of criteria is established for quantitative estimates of scheme properties.

A PC-oriented Emergency Response System (BERS) is developed and works at the National Institute of Meteorology and Hydrology with the Bulgarian Academy of Science. The creation and the development of BERS were highly stimulated by ETEX (European Tracer Experiment).

ERS consists of two main parts — operational and accidental ones, realized for both regions “Europe” and “Northern Hemisphere”. The operational part runs automatically twice a day after new analysis and forecast meteorological data are received via GTS of WMO. It prepares the current met-files, calculates trajectories for selected NPP, visualizes the results and puts the pictures in a specialized Web-site. The accidental part is activated manually when real radioactive releases occur or during emergency exercises. The source term is specified by the users — Bulgarian emergency authorities. The EMAP model is the core of this part. This is a 3-D Eulerian dispersion model producing concentration and deposition fields. The visualized output is sent back via fax and/or specialized ftp-site.

In the paper, the BERS overall structure and modules are described and its applications in emergency management are shown. Special emphasis is made on BERS performance during the runs of the EC 5FP project ENSEMBLE.

The TM5 atmospheric chemistry-transport model has been developed to study the interaction between the global and regional scales. It is an off-line model with a spatial global resolution of 6° × 4° and a two-way zooming algorithm that allows a finer resolution of 1° × 1° over selected regions (e.g. Europe, N. America, Africa and Asia). Photochemistry and aerosols are coupled in this version of the model. Aerosols, which can contain sulphate, ammonium and nitrate, are described using a bulk approach. The equilibrium model EQSAM is used to calculate the partitioning between the aerosol and gas phases. Preliminary results of the model application for the year 2000 over Europe are presented. The annual average modelled concentrations of sulphate, ammonium and nitrate are compared to the measurements from the EMEP stations. Generally the comparison with observations indicates that too low SO and too high SO concentrations are found. Modelled nitrate and ammonium concentrations are also high compared to EMEP measurements.

Two atmospheric boundary layer (ABL) models developed in agreement with the similarity theory are applied: YORDAN - for stable and neutral conditions and YORCON - for convective cases. Both models consist of a surface layer and an overlying Ekman layer. The vertical profiles of the temperature, wind velocity and the turbulent exchange coefficient in the ABL can be obtained applying the models. A proper parameterization is developed in both cases applying the resistance laws for stable, neutral and convective conditions. The relation between the external and internal to ABL parameters are given by the resistance laws numerically solved in both models. The input parameters for the models are obtained from the experimental data applying two approaches: the first one (called “top-down” approach) uses data for the geostrophic wind and the potential temperature. The second one (called “bottom-up” approach) uses data from the surface meteorological observations.

Discussions were scheduled within the program of the NATO Advanced Research Workshop on “Advances in Air Pollution Modelling for Environmental Security”. Three major topics were discussed: (a) the use of more powerful computers in the treatment of some large-scale environmental models, (b) the application of data assimilation techniques for improving the output from the models and (c) the need of better emission inventories. The major conclusions from these discussions well be presented in this paper.