A 3-D high-order accurate time-stepping scheme for air pollution modelling

Abstract

In this work a 3-D model for pollutant transport in the atmosphere is proposed. We consider a set of coupled convection-difíusion equations including the reactions of the pollutant species. In particular, the modelling of oxidation and hydrolysis of sulphur and nitrogen oxides released to the surface layer is studied. The convective phenomenon is mainly produced by the wind field which is obtained from a 3-D mass consistent model. The dry deposition process is represented by the so-called deposition velocity, which is proportional to the degree of absorptivity of the surface, and it is assumed as constant along the vertical flow, and thus, it is introduced as a boundary condition. The wet deposition is simulated by a source term in the convection-diffusion equations using the washout coeíRcient. To obtain a numerical solution, first, the problem is transformed using a conformal coordinates system. This allows us to work with a simpler domain in order to build a mesh that provides high consistency for finite difference schemes. Then, the convection-diffusion equations are solved using a high order time discretization with a finite differences scheme.