84th AMS Annual Meeting

Monday, 12 January 2004
Applications of the Multi-Scale Global/Regional Atmospheric Heavy Metals Model (GRAHM) to mercury transport
Hall 4AB
Didier Davignon, MSC, Environment Canada, Dorval, QC; and A. Dastoor
GRAHM model's on-line design is presented, along with applications to Arctic tropospheric mercury depletion and atmospheric mercury source-receptor studies. GRAHM benefits from Canadian Meteorological Center's comprehensive weather forecast model GEM, offering a detailed representation of cloud water, boundary layer and surface. It includes global multi-level anthropogenic emissions, background natural and recycled emissions. dry and aqueous-phase chemical processes for mercury, dry deposition and precipitation scavenging.

GRAHM was used to assess yearly budgets over Arctic when taking into consideration mercury depletion events observed at springtime. Local depletion events were included where sea ice and solar radiation were available. As a result, total mercury deposition north of Arctic circle was increased by roughly 44%. Modelled time series of surface concentrations compare well with observed values.

Another application of the model is source-receptor studies. Contributions from Canada, USA, Europe, North-Eastern Asia, natural and recycled emissions to selected areas were assessed. Major emitters are shown to have a significant remote impact on total deposition.

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