SIMULATION OF DISPERSION IN MODERATELY COMPLEX TERRAIN .A. THE FLUID DYNAMIC-MODEL

A three-dimensional time dependent model for the meso-γ-scale based on finite difference solution of the hydro-, thermodynamical and turbulent energy equations is presented. The present version of the model is hydrostatic and has a prescribed surface temperature input. Simulations with the model have been done for an area in southern Sweden, the Vänerborg-Trollhättan region, where a series of measurements have been carried out with the specific aim in mind to obtain test data for the model. The geographical area is characterized by topographical features on the meso-γ-scale, i.e. 2-20 km. Thus there are forested hills, a relatively flat agricultural area, a river valley and an extended lake area within the model region. The terrain height relief is maximum 100 m and typically 50 m. The results from model simulations presented here are compared with measurements performed in the experimental area. The simulations show quite good agreement with the measured data both for the mean quantities and for the turbulent energy in most of the cases. The results from the model simulations have been used as data for the higher order closure dispersion model presented in Part B and for the operational dispersion model presented in Part C. © 1990.