High-resolution model simulations of anthropogenic sulphate and sulphur dioxide in Southeast Asia

The Multiple-scale Atmospheric Transport and CHemical modelling system (MATCH)—driven by meteorological data from the ECMWF—has been applied to a model domain covering Southeast Asia to complete a simulation extending over the full year of 2000. The current paper presents an evaluation of the model performance using archived chemical and meteorological data collected in the region during the year 2000. The calculated sulphate concentrations (on atmospheric aerosols and in precipitation) compare reasonably with observations while the atmospheric SO2 mixing ratios show worse correspondence. This latter mismatch is attributed to local variations in the measured SO2 concentrations that are not resolved in the regional model and possible miss-location of the emissions in our model. It can also be pointed out that different laboratories measuring SO2 at the same site occasionally report SO2 concentrations that differs by an order of magnitude or more.The seasonal variations of the modelled species are less than initially expected but generally in accordance with the measurements available. Most of the Malaysian cities have comparatively low concentrations of sulphate in precipitation. This is supported both by the model results and by independent measurements. From the model simulations and the measurements, it is concluded that the sulphur deposition is still relatively low (i.e. <0.5 g sulphur m−2 year−1) in most of rural Malaysia. This is also the case in Myanmar, Laos, central Vietnam, Kampuchea and southern Thailand. The situation in the vicinity of the large cities in the region is, however, much worse and the deposition is similar, or larger, than estimated critical loads.