Summary
As part of a model intercomparison exercise, with participants from a number of Asian, European and American institutes, sulphur transport and conversion calculations were conducted over an East Asian domain for 2 different months in 1993. All participants used the same emission inventory and simulated concentration and deposition at a number of prescribed geographic locations. The participants were asked to run their respective model both with standard parameters, and with a set of given parameters, in order to exarnine the different behaviour of the models. The study included comparison with measured data and model-to-model intercomparisons, notably source-receptor relationships.
We hereby describe the MATCH model, used in the study, and report some typical results. We find that although the standard and the prescribed set of model parameters differed significantly in terms of sulphur conversion and wet scavenging rate, the resulting change in atmospheric concentrations and surface depositions only change marginally. We show that it is often more critical to choose a representative gridbox value than selecting a parameter from the suite available.
The modelled, near-surface, atmospheric concentration of sulphur in eastem China is typically 5-10 μg S m-3, with large areas exceeding 20 μg S m-3. In southem Japan the values range from 2-5 μg Sm-3. Atmospheric SO2 dominates over sulphate near the emission regions while sulphate concentrations are higher over e.g. the western Pacific. The sulphur deposition exceeds several g sulphur m-2 year-1 in large areas of China. Southem Japan receives 0.5-1 g S m-2 year-1. In January, the total wet deposition roughly equals the dry deposition, in May - when it rains more in the domain - total wet deposition is ca. 50% larger than total dry deposition.