Coupling the Photochemical, Eulerian Transport and ‘Big-Leaf’ Deposition Modelling in a Three Dimensional Mesoscale Context

In this paper we show the different modules of an air dispersion modelling study for the Madrid Area. We show the general background of a non-hydrostatic meteorological mesoscale model as a key module for obtaining the wind, temperature and humidity fields by using a k-Theory turbulence model. Because we solve the pressure in the vertical axe, we have to solve explicitly the Helmohltz equation because the complexity of the terrain (in a general sense) request to use the so-called ”terrain following coordinates”. This approach introduces non linear terms in the first and second order spatial coordinates which complicates the solution of the Helmohltz equation, Pielke (1984). The solar radiation module is also essential for knowing the radiation -in all the wave lengths-at every cell of the three dimensional domain. This radiation -global, diffuse, scattered and net-allows to parameterize the complex photochemical reactions which are undergoing in the atmosphere engined by the solar radiation. This photochemical package works in parallel with the prognostic and diagnostic meteorological model by using different time steps.