IMAGES: a three-dimensional chemical transport model of the global troposphere

Abstract

A new three-dimensional chemical transport model of the troposphere is presented. This model, named intermediate model of global evolution of species (IMAGES) has been developed to study the global distributions, budgets, and trends of 41 chemical compounds, including the most important species that determine the oxidation capacity of the atmosphere. The model accounts for surface emissions, chemical transformations, dry and wet deposition, and aerosol reactions of trace constituents. The model is formulated in sigma coordinates and includes 25 layers in the vertical. Its horizontal resolution of 5 degrees in longitude and 5 degrees in latitude. To keep the requirements in computer time limited, a simplified representation of the transport is adopted: the advection, solved by a semi-Lagrangian scheme, is driven by monthly mean climatological winds provided by an European Center for Medium-Range Weather Forecasts analysis. The effect of wind variability at timescales smaller than a month is taken into account by an eddy diffusion parameterization. Convection in cumulonimbus clouds is also represented. (from Authors)