A Tracer Dispersion Model Driven by Global-Scale Analyses and Mesoscale (MM5) Model Output and Its Validation with Tracer Experiment Data

Larger-scale tracer transport and dispersion model simulations with lower resolution (1 degree) frequently suffer from unresolved terrain variability. The smoothing of the topography causes an underestimate of vertical transport in complex terrain. We test two different parameterisations, one based on terrain variability within one grid cell only, and one based on terrain variabililty plus local stability. For a validation, we compare results obtained with the Lagrangian particle diffusion model FLEXPART with measurements during tracer release experiments. For some cases, we perform high-resolution nested-grid model simulations and compare results for the different nests.