Application of a Refined Emergency Code System SPEEDI to Atmospheric Field Experiments Conducted over a Complex Terrain





An environmental emergency code system SPEEDI consisting of a mass consistent wind field model and a lagrangian particle dispersion model is taken up for validation study using the benchmark data obtained from a series of field experiments conducted over a complex terrain. During the experiments extensive data on meteorological parameters were collected and in addition SF<SUB>6</SUB> tracer gas was released and sampled by thickly distributed samplers. An isolated hill placed on an otherwise flat terrain provides a special geometrical situation so that the data can be used for testing the model simulation of stream line deflections past an obstacle. An objective basis for relating the ratio of Gauss precision moduli which controls the horizontal to vertical adjustment of the wind components has been introduced in the wind field model and the results show great improvement particularly when the parameter is allowed to vary with height. Results of the tracer release experiments confirm the improvements. The modified wind field model is then coupled with the lagrangian particle dispersion model. Diffusion calculations are carried out using locally obtained empirical diffusion parameters similar to the traditional Pasquill-Gifford parameters and as well as the observed turbulence information. Better accuracy is seen in the calculation of tracer concentration distribution in the latter case. While the code retains the merit of quick and effective use of routine measurements, the general performance is expected to improve when these changes are incorporated in it.


  • Journal of nuclear science and technology

    Journal of nuclear science and technology 33(2), p.157-165, 1996-02-25

    Atomic Energy Society of Japan

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