Experimental verification study for system for prediction of environmental emergency dose information: SPEEDI, 3

The performance of a three-dimensional atmospheric transport and diffusion model to simulate an accidental release of radioactivity was evaluated by data sets from field tracer experiments over a mountain and valley area. The model consists of a mass-consistent model for wind fields and a particle random-walk model for atmospheric dispersion. Model simulations of tracer concentrations were compared with observed values from eleven experiments; four were conducted in down-valley winds; two were in up-valley winds and five were in cross-valley winds. The calculated results almost agreed reasonably with observed concentration patterns. However, it bacame apparent that the model is subject to err from real dispersions in down-vally winds induced by nocturnal drainage flows. (author)