AN EVALUATION OF THE ADOM CLOUD MODULE

The Acid Deposition and Oxidant Model (ADOM) is an Eulerian long-range transport and deposition model. One of the most highly parameterized and least well established parts of the model is the scavenging module that describes cloud formation, pollutant scavenging, aqueous-phase c hemistry and wet deposition. As a means of gaining insight into the sc avenging module, results from simulations with the module are compared with the results from simulations for equivalent conditions with a th ree-dimensional dynamic cloud chemistry model. Comparisons of results for a variety of initial conditions show that wet deposition of sulpha te, nitrate and ammonium ions tend to be underpredicted by the scaveng ing module and that the pH of the rain is overpredicted. Although the differences are for the most part not large, they are sensitive to clo ud top height. The amount of hydrogen peroxide deposited at the surfac e is significantly smaller in the ADOM module than in the cloud chemis try model. For the particular conditions that are considered, oxidatio n is limited by the hydrogen peroxide concentration for the cloud chem istry model, but by the sulphur dioxide concentration for the ADOM mod ule.