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J. Chen et al.
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.
18.1 GEM-MACH-Global Model
GEM-MACH is the air quality model of Environment and Climate Change Canada
(ECCC). It is a chemistry extension to the current Department’s operational numerical weather prediction system [1, 2]. The model is an online, one-way coupled
meteorology-chemistry model with a latitude-longitude (Arakawa C) grid and a
staggered-hybrid vertical coordinate system. The model has 80 vertical layers with
model top at 0.1 hPa. Approximately 9 layers are below the first 1 km. GEM-MACH’s
atmospheric chemistry components include full process representation of oxidant
chemistry with gas-, aqueous-, heterogeneous-chemistry, and dry and wet deposition of gases. Aerosol chemistry and physics are from the Canadian Aerosol Module
[3]. The gas-phase chemistry is based on the ADOM2 mechanism which was shown
to offer an adequate representation of the chemistry of a polluted continental troposphere [4] but was inadequate for global scale representation as it lacks several key
reactions in the UTLS region that are necessary for using the model forecasts as trial
fields towards operational NOy and O 3 chemical data assimilation.
The following sections describe the work in progress to improve the formulation
of GEM-MACH for its use at the global scale (GEM-MACH-Global). Innovations
include a revised gas-phase mechanism, the adoption of a flexible photolysis module
and the introduction of lightening NOx emissions. Preliminary results of an annual
evaluation of the model are presented.
18.1.1 New Gas-Phase Chemistry
A new chemical mechanism based on the condensed version of SAPRC-07, CS07A
[5] was incorporated into GEM-MACH-Global utilizing the Kinetic PreProcessor
(KPPv2.2.3) with the rodas3 Rosenbrock solver [6]. To CS07A, the following reactions and their rate equations were added specifically for the UTLS region:
J. Chen et al.
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.
18.1 GEM-MACH-Global Model
GEM-MACH is the air quality model of Environment and Climate Change Canada
(ECCC). It is a chemistry extension to the current Department’s operational numerical weather prediction system [1, 2]. The model is an online, one-way coupled
meteorology-chemistry model with a latitude-longitude (Arakawa C) grid and a
staggered-hybrid vertical coordinate system. The model has 80 vertical layers with
model top at 0.1 hPa. Approximately 9 layers are below the first 1 km. GEM-MACH’s
atmospheric chemistry components include full process representation of oxidant
chemistry with gas-, aqueous-, heterogeneous-chemistry, and dry and wet deposition of gases. Aerosol chemistry and physics are from the Canadian Aerosol Module
[3]. The gas-phase chemistry is based on the ADOM2 mechanism which was shown
to offer an adequate representation of the chemistry of a polluted continental troposphere [4] but was inadequate for global scale representation as it lacks several key
reactions in the UTLS region that are necessary for using the model forecasts as trial
fields towards operational NOy and O 3 chemical data assimilation.
The following sections describe the work in progress to improve the formulation
of GEM-MACH for its use at the global scale (GEM-MACH-Global). Innovations
include a revised gas-phase mechanism, the adoption of a flexible photolysis module
and the introduction of lightening NOx emissions. Preliminary results of an annual
evaluation of the model are presented.
18.1.1 New Gas-Phase Chemistry
A new chemical mechanism based on the condensed version of SAPRC-07, CS07A
[5] was incorporated into GEM-MACH-Global utilizing the Kinetic PreProcessor
(KPPv2.2.3) with the rodas3 Rosenbrock solver [6]. To CS07A, the following reactions and their rate equations were added specifically for the UTLS region: