The Canadian Meteorological Centre's integrated emergency response system for modelling atmospheric transport and dispersion of pollutants

The Environmental Emergency Response (EER) Section of the Meteorological Service of Canada's Canadian Meteorological Centre (CMC) has a mandate to provide operational guidance in support to environmental emergencies involving atmospheric transport and dispersion of pollutants. The section manages an operational system capable of addressing transport and dispersion problems on a wide range of geographic scales ranging from complex urban environments to global scales. The list of pollutants includes radioactive material, volcanic ash, smoke form forest fires, releases from chemical fires and industrial accidents and CBRN (Chemical Biological Radiological Nuclear) related releases. To achieve this mandate the EER Section runs a suite of atmospheric transport and dispersion models (MLCD, MLDP0, MLDP1) that are coupled with the meteorological fields provided by CMC's operational regional and global analysis and forecast systems.

During the past five years, through funding from Defence R&D Canada's CRTI (CBRN Research and Technology Initiative) program, a transport and dispersion modelling capability was developed to address the problems of dispersion at the urban scale. The prototype system (CUDM- Canadian Urban Flow and Dispersion Modeling) is a multi-scale system that aims to simulate the mean flow, turbulence and concentration fields in urban areas. The system involves a cascade of meteorological models from the operational regional model to an urbanized meso-scale model (UrbanGEM), that in turn drives a CFD flow model running at the urban scale (UrbanSTREAM). This micro-scale model simulates mean wind and turbulence fields that can feed an Eulerian dispersion model (UrbanEU) and/or a Lagrangian Stochastic dispersion model (UrbanLS). The latter two models can make predictions of concentration fields resulting from releases of contaminants such as CBRN agents. The prototype CUDM system has been validated using the Joint Urban 2003 Oklahoma City campaign and has been tested on some Canadian cities, including Vancouver, Ottawa, and Montreal. It will be a key element in the EER section's support for the 2010 Vancouver Winter Olympics.

Work is on-going to examine how to use the output of the down-scale modeling cascade to move the hazardous material beyond and downwind from the urban setting. Simple approaches are being investigated by using the output of the CUDM as a source term for the broader resolution regional dispersion models. Work is also on-going to include improved wet and dry deposition schemes and better assessment of situations in complex topography areas. The integrated system approach between the transport and dispersion tools and the meteorological modeling is leading to further R&D work on improving the higher resolution meteorological models.