A mesoscale atmospheric model with horizontal subgrid for chemical transport

Abstract

By implicating two supplementary modules, a mesoscale non-hydrostatic model of atmosphere was qualified to simulate the chemical transport at resolutions much higher than the model grid. Compared with standard fine-grid applications, this method proves to be nearly so efficient but more economic. The modules solve the chemical transport equations (a) and supply the horizontal subgrid (b) for the meteorological and chemical calculations: (a) The chemical transport module considers the triad NONO203 together with a simplified hydrocarbon chemistry. The chemical reactions, anthropogenic and biogenic emission, dry deposition, passive transport, and turbulent diffusion are involved. For these calculations a special vertical subgrid was introduced within the lowest atmospheric model layer. It eliminates the frequently used approach of constant vertical particle fluxes near the surface.(b) The horizontal-subgrid module splits the horizontal model grid equidistantly into subgrid cells. The vertical surface fluxes of momentum, sensible and latent heat, radiation, soil heat and wetness, and chemical components are explicitly treated on this subgrid. The subgrid-averaged surface fluxes are employed for the (coarser) model-grid calculations of the atmospheric meteorological variables. In contrast to the meteorological quantities, the chemical components and processes are performed at all model layers on the horizontal subgrid.Several results of the method described are compared to conventional simulations of variable resolution.