Air quality modelling

Environment Canada’s air quality research team includes research scientists who are internationally renowned for their work on air quality modelling. The Department carries out modelling research on the transport, transformation and deposition of pollutants by the atmosphere. Air quality models are developed on the global, regional and local scale, and are used to predict the short-term and long-term concentrations of atmospheric pollutants based on the emission levels of these pollutants and/or their precursors.

Contributing to Policies and Decision-making

The development and application of effective air quality models help integrate our understanding of the physical and chemical processes of air pollutants and provides important science support for policy decision-making.  Examples of how Environment Canada’s air quality modelling activities have supported national and international policies include:

• Environment Canada’s air quality modelling activities are providing important forecasting data to Canada’s Air Quality Health Index, used by Canadians for health-related decision-making.
• The results from modelling the trends of usage and emissions of semi-volatile organic compounds, combined with on-the-ground sampling and measurement programs, provided support to the development of the Stockholm Convention on Persistent Organic Pollutants(POPs).   
• The transboundary movement of air pollutants are also being integrated into models to predict the impact on Canada of sources in Asia, Europe, and Africa.  This information helps support Canadian participation and negotiations within the United Nation’s Convention on Long-range Transboundary Air Pollution and its Task Force on Hemispheric Transport of Air Pollution.
• Smog and acid rain components of Canada’s air quality models provided scientific support to negotiators for the Agreement between the Government of Canada and the Government of the United States of America on Air Quality.  The Agreement also commits Canada and the United States to carrying out scientific and technical activities to improve their understanding of transboundary air pollution concerns and to increase their capability to control such pollution.
• Results from Environment Canada’s air quality modelling research contributed to the Government of Canada’s document Turning the Corner:  Regulatory Framework for Air Emissions and related clean air priorities examining levels of emission reductions.

Contributing to Other Scientific Activities

Air quality modelling plays an important role in the integrated assessment of air quality issues contributing to a strengthening of the understanding and characterization of air pollution and eventually to well-informed air quality management decisions and strategies.  Examples of how Environment Canada’s air quality modelling activities contribute to other scientific activities include:

• Accurate models are needed to help interpret data and measurements from air quality monitoring programs and to help guide sampling procedures.  The models can also complement the monitoring programs by estimating deposition over large regions where it may not be feasible or cost effective to take on-site measurements. 
• Model predictions and forecasts are used to guide field studies and maximize the cost- and time- effectiveness of those studies. 
• Together with Environment Canada’s effective monitoring networks and data, air quality models are used to obtain comprehensive source attribution information - to know not only how much pollution is being deposited at any location, but also where it came from.
• The scientists are using the models to predict particular occurrences or phenomena that we may not be able to identify through observations (for example, modelling of occurrences of smog is complex, but it is valuable for predicting future smog episodes).
• Environment Canada’s air quality models are used to help predict the impact of urban planning decisions, such as the placement of roads and the location or expansion of industrial areas.
• Air quality models are being coupled with climate change models, in recognition that climate change can impact gas- and aerosol-phase chemistry, transport, and cloud processes which, consequently, may impact the formation and distribution of both ozone and particulate matter.  Environment Canada scientists are combining two existing numerical models, the Canadian Regional Climate Model and A Unified Regional Air-quality Modelling System to study the effects of climate change on air quality at a 42 km resolution over North America.

Air Quality Forecasting in Action

Environment Canada’s current operational air quality forecast model is Global Environmental Multi-scale - Modelling air quality and Chemistry (GEM-MACH).  For more information on this model and how it provides guidance for the production of air quality forecasts for Canadians, see our Air Quality Model Forecasts.