GEM-AQ, an on-line global multiscale chemical weather modelling system: model description and evaluation of gas phase chemistry processes

Abstract

Abstract. Tropospheric chemistry and air quality processes were implemented on-line in the Global Environmental Multiscale weather prediction model. The integrated model, GEM-AQ, was developed as a platform to investigate chemical weather at scales from global to urban. The current chemical mechanism is comprised of 50 gas-phase species, 116 chemical and 19 photolysis reactions, and is complemented by a sectional aerosol module with 5 aerosols types. All tracers are advected using the semi-Lagrangian scheme native to GEM. The vertical transport includes parameterized subgridscale turbulence and large scale deep convection. Dry deposition is included as a flux boundary condition in the vertical diffusion equation. Wet deposition of gas-phase species is treated in a simplified way, and only below-cloud scavenging is considered. The emissions used include yearly-averaged anthropogenic, and monthly-averaged biogenic, ocean, soil, and biomass burning emission fluxes, as well as NO x from lightning. In order to evaluate the ability to simulate seasonal variations and regional distributions of trace gases such as ozone, nitrogen dioxide and carbon monoxide, the model was run for a period of five years (2001)(2002)(2003)(2004)(2005) brid levels extending up to 10 hPa. Model results were compared with observations from satellites, aircraft measurement campaigns and balloon sondes. We find that GEM-AQ is able to capture the spatial details of the chemical fields in the middle and lower troposphere. The modelled ozone consistently shows good agreement with observations, except over tropical oceans. The comparison of carbon monoxide and nitrogen dioxide with satellite measurements emphasizes the need for more accurate, year-specific emissions fluxes for biomass burning and anthropogenic sources. Other species also compare well with available observations.

Online coupled regional meteorology chemistry models in Europe: current status and prospects

“…modes), mineral (nuc./ acc./ coa. modes), mineral (transported), sulfate droplets C: Grid and sub-grid scale bulk G: None A: Only through temperature change caused by LW/SW C: Grid and sub-grid scale bulk SW, LW, PH: Model time step GEM Kaminski et al (2008) Correlated K (Li and Barker, 2005) with O3, H2O and aerosols from chemistry Correlated K (Li and Barker, 2005) with O3, H2O and aerosols from chemistry G,A,C all taken into account in Jvalue calculations using method of Landgraf and Crutzen, 1998 SW, LW, PH: model time step Lafore et al (1998) G: Climatology for O3 (Fortuin and Langematz, 1994), constant background for CO2, CH4, N2O, CFC11,CFC12 A: With prognostic aerosol (Tulet et al, 2005) , radiative properties of aerosols according to Mie theory (Aouizerats et al, 2010). Without aerosol scheme, climatological aerosols.…”

Impact of urban parameterization on high resolution air quality forecast with the GEM – AQ model

“…The forecasting system is based on the GEM-AQ model (Kaminski et al, 2008). GEM-AQ is a numerical weather prediction model where air quality processes (gas phase and aerosols) are implemented on-line in the host meteorological model, the Global Environmental Multiscale (GEM) model, developed at Environment Canada (Côté et al, 1998).…”

Evaluation of the GEM-AQ model in the context of the AQMEII Phase 1 project

“…As the GEM-AQ model used in this study has been extensively documented elsewhere (Côté et al, 1998a, b;Mailhot et al, 2006;Kaminski et al, 2008;Gong et al, 2012), we shall focus on the model configuration choices used in this study. The meteorological component of the system, the GEM model, is a medium-range operational weather forecast model of the Canadian Meteorological Centre.…”

“…For a complete list of species and reactions, see Kaminski et al (2008). A simplified aqueous-phase reaction module allows for oxidation of SO 2 to sulphate.…”

“…As a part of Phase 1 of the AQMEII project, a simulation of air quality in Europe was conducted using the Global Environmental Multiscale Air Quality model (GEM-AQ, Kaminski et al, 2008). This model differs from other Phase 1 participating models in two aspects.…”