The ECHMERT model
A global atmospheric circulation model, ECHMERIT, with coupled meteorology and atmospheric chemistry including mercury has been developed. The model is designed to study in detail the atmospheric physical and chemical processes which influence the atmospheric lifetime of mercury, and therefore its global deposition patterns. ECHMERIT, based on the Global Circulation Model (GCM) ECHAM5 differs from most global mercury models in that the emissions, chemistry, transport and deposition are coupled on-line to the GCM. Many atmospheric chemistry models treat meteorological and chemical processes separately, in giving the meteorological conditions to the CTM in relatively coarse temporal resolutions. Their coupling in ECHMERIT avoids temporal and spatial interpolation, which permits more accurate representation of the interaction between chemical and meteorological phenomena, providing more highly resolved (temporal and spatial) meteorological fields. The coupling of the modules has been achieved in a modular way keeping the model as flexible as possible. This flexibility allows the model to be run with different levels of complexity. An example of a process for which a more detailed impact study could improve understanding of the atmospheric Hg cycle is biomass burning, which involves emission, reaction, gas-particle partitioning and deposition of Hg. At present ECHMERIT is being used within the HTAP Task Force to contrast and compare the performance of different models in a series of passive tracer transport experiments. Modelling experiments with extensive Hg chemistry, with both wet and dry deposition included, to assess the consequences of emission scenario changes for different Hg source areas are being evaluated.
KeywordsMercury Concentration Biomass Burning Atmospheric General Circulation Model Receptor Region Mercury Species
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