Development and Current Status of the GEM-MACH-Global Modelling System at the Environment and Climate Change Canada

The GEM-MACH-Global model is a global online meteorology-chemistry system currently being developed at the Department of Environment and Climate Change Canada (ECCC). The model is an extension of the Department’s operational, regional GEM-MACH numerical weather and air quality prediction system. The objectives for its development are to improve our understanding of the long range transport and fate of criteria air contaminants, and to improve our forecasting system by providing chemical boundary conditions for the regional air quality forecast system, and background fields for global chemical data assimilation (O3 and NOy species). For this purpose, GEM-MACH-Global was recently updated with a comprehensive photolysis module (JVAL14-MESSy) and a detailed gas-phase chemistry module based on the SAPRC07C mechanism. Compared to its original ADOM2 chemistry mechanism, the revised gas-phase chemistry is more explicit, with new species and ~15 additional reactions important in the upper troposphere and lower stratosphere (UTLS) region. Furthermore, a lightning emission module was incorporated to represent NOx emissions aloft. These changes were evaluated with a 2010 annual simulation on a 400 × 200 global-grid. The simulation included inputs from 2010 HTAP global anthropogenic emissions, GFEDv3 biomass burning emissions and ECCC’s operational meteorological analyses. The presentation will describe the current state-of-science development of GEM-MACH-Global and show comparisons results of the annual simulation.