Regional Specialized Meteorological CentreRSMC MONTRÉAL
IntroductionThe First International Workshop on Users' requirements for the Provision of Atmospheric Transport Model Products for Environmental Emergency Response was held in Montréal in September 1993. The workshop Proceedings (1) recognized the need for a standardization of procedures and products. It was decided that the designated Regional Specialized Meteorological Centres (RSMCs) would develop and maintain user interpretation guidelines on atmospheric transport models and distribute it to the delegated authorities, IAEA and WMO. This document is written to meet this objective.
The Canadian Meteorological CentreRSMC Montréal is located at the Canadian Meteorological Centre (CMC) which is the national meteorological centre for Canada. The CMC operates around the clock and provides a variety of essential numerical weather prediction (NWP) products and services in Canada; it also manages the supporting national computing and telecommunications networks and facilities as well as the national climate archives. The atmospheric component of the federal environmental emergency response program for Canada is also managed from this Centre. At CMC, the meteorological and systems development and research personnel work closely with operations staff to ensure that the operational requirements are met and that the operational numerical weather prediction systems are at the leading-edge of science and technology. CMC runs its operational suite of computer analyses and forecast models on a supercomputer and several UNIX front-end machines. Telecommunications functions are provided by Tandem computers, with a GTS link to the Washington Telecom Hub and a backup link to Bracknell. Experienced meteorologists, computer specialists, and technical staff perform operational duties around the clock to monitor and control the NWP forecast production and dissemination systems. Other specialists are on call to lend additional support, for example, in the event of a major environmental emergency. The production system for atmospheric transport modelling benefits from all of the Centre's operational facilities and tools which are part of the well established NWP forecast production system, including operator interfaces, sophisticated interactive computer graphics for output visualization, chart and text generation and dissemination. At the same time, current global weather conditions and forecasts are always available to provide the necessary basis for interpreting and evaluating the atmospheric transport of radioactive clouds in all WMO Regions. The CMC has two main NWP model in operations: a regional model and a global spectral model. The latter, which has a uniform resolution over the globe, is used to provide quality analyses, through the assimilation cycle, and medium term forecast guidance. From this model, a very comprehensive set of graphical and alphanumeric products is available. The CANERM ModelCANERM, the CANadian Emergency Response Model, is a fully 3-dimensional Eulerian model for medium and long range transport of pollutants in the atmosphere. A detailed description of the model can be found in Pudykiewicz (1). Advection is calculated using the semi- Lagrangian method. Diffusion is modelled according to the gradient (K) theory; diffusivities in the horizontal and in the vertical are dependant on the state of the boundary layer at low levels, and constant in the free atmosphere. The model simulates wet deposition resulting from scavenging by clouds and precipitation. Dry depostion is also simulated by a dry deposition velocity which accounts for the resistance of the turbulent and laminar layers very near the surface. The source of emission is modelled according to the concept of a virtual source (Pudykiewicz, (2)) to account for unresolved subrid effects near the point of release. The virtual source is expressed as a 3-D Gaussian function. A variety of atmospheric pollutant can be tracked, including radioactive species and volcanic ash. CANERM operates on a polar stereographic grid and can be executed on the Northern Hemisphere and on the Southern Hemisphere. The horizontal resolution is 150 km in the hemispheric configuration, 50 km in the continental configuration, and 25 km in the regional configuration. The model has 11 vertical levels in the SIGMA terrain following coordinates.
Default scenario conditions and interpretation of the outputsThe default source parameters used for the initial run of the model are defined in attachment 2 of the Montréal Workshop Proceedings. They are:
This concept is based on the understanding that the first (initial) run of the transport/dispersion models needs to be carried out with default parameters because little or no information (except location and possibly accident time) will be available at the early stage. RSMC Montréal would however prepare the subsequent model runs with more realistic parameters as they become available. however, the initial run will always use the default scenario conditions. A word of caution is needed about the interpretation of the CANERM outputs. The default scenario is based on a hypothetical source as specified above. In the case of an unconfirmed event, the existence and strength are unknown. Even when an event is confirmed, the strength may remain unknown. The users should bear this in mind when analyzing the outputs. Although CANERM is run from a high quality NWP model, inherent uncertainties must be considered as a result of the default scenario conditions and the atmospheric conditions. The CANERM model output interpretation must be done with this in mind, given the fact that the source strength and duration are usually not known. The interpretation should be done with the help of an experienced meteorologist having a strong background in synoptic meteorology and also desirably with a background in atmospheric dispersion. Even in the case of an event confirmed by the IAEA and better estimates of the source, caution is advised as to the interpretation of the outputs. This being said, model outputs offer the best available guide in a first response situation to the question of long range atmospheric dispersion and transport of radioactive clouds. Radiological observations should be used as soon as they become available to provide collaborative information with model outputs.
Description of the CANERM output maps for the default scenarioFigure 1 presents an output map as obtained from a CANERM forecast using the default scenario. Here is a description of what it contains:
Complete set of CANERM output maps for the default scenarioFigures 2 to 5 present a complete set of output maps for the default scenario. For these maps, the following items are identical:
Figure 2 is the 24 hours time integrated surface to 500 m layer concentration for the period ending 24 hours after the time for which the initial data is available for the model run. In this case, the 24 hour period ends 17 October at 12Z (UTC).
Figure 3 is the 24 hours time integrated surface to 500 m layer concentration for the period ending 48 hours after the time for which the initial data is available for the model run. In this case, the 24 hour period ends 18 October at 12Z (UTC). Note that the four concentration contours are different from the ones in figure 2.
Figure 4 is the 24 hours time integrated surface to 500 m layer concentration for the period ending 72 hours after the time for which the initial data is available for the model run. In this case, the 24 hour period ends 19 October at 12Z (UTC).
Figure 5 is the total deposition in 72 hours for the period ending 72 hours after the time for which the initial data is available for the model run. In this case, the 72 hour period ends 19 October at 12Z (UTC).
Finally, Figure 6 presents the three dimensional trajectories starting at 15Z (UTC) on 16 October at heights of 500 m (950 hPa), 1500 m (850 hPa) and 3000 m (700 hPa) above Pickering. The forecasted trajectories are presented every 3 hours and end at 12Z (UTC) on 19 October. Other products available from RSMC Montréal and contact for additional informationMany other products can be produced by RSMC Montréal if the situation requires it. For example, instantaneous surface and upper air concentration maps are available. These products go beyond the scope of this document and will not be described here. However, they may be included in subsequent versions. For any additional information regarding CANERM, please contact :
Created :
2002-08-26
Modified :
2002-12-18
Reviewed :
2002-12-18
Url of this page : http://www.msc.ec.gc.ca
/cmc/eer/RSMC/guide_e.html The Green LaneTM, |
The default navigational mode of this site requires either [MSIE 4+], [Netscape 6+], [Opera 5+] or equivalent with JavaScript enabled. If you can not upgrade your browser, or can not enable JavaScript, please use the [text-only] version of this site.