Coupling of mesoscale and microscale models—an approach to simulate scale interaction

Atmospheric flow and pollutant dispersion over built-up areas are affected by phenomena occurring at different scales. Hence, scale interactions should also be considered in the mathematical modelling of atmospheric flow and pollutant dispersion. In this paper a method is presented to couple prognostic mesoscale and microscale flow models. Results from mesoscale simulations are used to generate the initial state and boundary conditions for microscale simulations. The method comprises a three-dimensional interpolation scheme and a vertical adjustment of the interpolated quantities in the surface layer based on similarity theory. The method is applied to couple the microscale model MIMO with the mesoscale model MEMO. The coupled system MEMO–MIMO is applied to simulate the local scale flow for an industrial area in southwestern Germany. Model results are presented and compared with available measurements.