Environmental Emergency Response Division

Regional Specialized Meteorological Centre

RSMC MONTRÉAL
USERS' INTERPRETATION GUIDELINES
ATMOSPHERIC TRANSPORT MODEL OUTPUTS
Version 4
OCTOBER 1995

• Introduction

• The Canadian Meteorological Centre

• The Canadian Emergency Response Model (CANERM)

• Default scenario conditions and interpretation of the outputs

• Description of the CANERM output maps for the default scenario

• Complete set of CANERM output maps for the default scenario

• Other products available form RSMC Montréal and contact for additional information

Introduction

The 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.

1. Environment Canada and World Meteorological Organization: PROCEEDINGS, FIRST INTERNATIONAL WORKSHOP ON USERS' REQUIREMENTS FOR THE PROVISION OF ATMOSPHERIC TRANSPORT MODEL PRODUCTS FOR ENVIRONMENTAL EMERGENCY RESPONSE, Montréal, Québec, Canada, 14-17 September 1993.

The Canadian Meteorological Centre

RSMC 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 Model

CANERM, 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.

1. Pudykiewicz, J., 1988. Numerical simulation of the transport of radioactive cloud from the Chernobyl nuclear accident. Tellus 40B, 241-259.
2. Pudykiewicz, J., 1989. Simulation of the Chernobyl dispersion with a 3-D hemispheric tracer model. Tellus 41B, 391-412.

Default scenario conditions and interpretation of the outputs

The default source parameters used for the initial run of the model are defined in attachment 2 of the Montréal Workshop Proceedings. They are:

• Uniform vertical distribution up to 500 m above the ground;
• uniform emission rate during the first 6 hours;
• Total pollutant release 1 unit (arbitrary);
• type of radionuclide CS 137.

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.

[View] (D)

Description of the CANERM output maps for the default scenario

Figure 1 presents an output map as obtained from a CANERM forecast using the default scenario. Here is a description of what it contains:

1. Identification of the source site or incident (source indicated by X on the map).

2. LAT= Latitude of the source site in degrees and hundredths of degrees. Positive for North, negative for South.

3. LONG= Longitude of the source site in degrees and hundredths of degrees. Positive for East, negative for West.

4. DATE OF RELEASE= Identifies the year, month, day and time of the release. The time is UTC (Universal Time Coordinate). If the time is unknown or uncertain, a default time (00 UTC or 12 UTC) and date will be used, both to be established through direct consultation between appropriate RSMCs.

5. Identification of the field that is plotted on the map. With the default scenario, the following maps are produced:

   1. 24 HRS TIME INTEG SURFACE TO 500M LAYER CONCENT. : Time integrated surface to 500 m layer concentration for the 24 hour period ending at 24 UTC (for a release occurring between 00 and 12 UTC) or ending at 12 UTC (for a release occurring between 12 and 24 UTC) for the date and time given in 6. The time integration is done within the 500 metres above the model ground.

      NOTE : For the first 24 hour period, the actual integration is done starting at the release time and ending at 12 UTC or 24 UTC. The time elapsed from the release to the end of the period will thus generally be less than 24 hours. However, since the value is an integrated one, it is the same as the value obtained when using a 24 hour integration. As an example, if the release occurs at 06 UTC, the 24 hour period for the integration will end at 24 UTC. The integrated value will result from the 06 to 24 UTC time period but it is the same as the contribution from 00 to 24 UTC (since the source is assumed to be zero between 00 and 06 UTC and hence, there is no contribution to the integrated value for that period).

   2. TOTAL DEPOSITION IN 72 HRS This is the total (wet and dry) deposition for the 72 hours ending at the date and time given in item 6.

6. Date and time at the end of the forecast period ("Z" is equivalent to UTC). The remaining indications are for internal use only at RSMC Montréal.

7. RELEASE SCENARIO Indicates that the information to follow describe the release scenario used by the model (items 8 to 18).

8. ISOTOPE: 137-CS Cesium 137 is used.

9. TIME FUNCTION: CONSTANT Function used to describe the behaviour of the release over time. In this case, the release is constant over the time period given in item 10.

10. DURATION: 6H The release has a duration of 6 hours.

11. HORIZONTAL DIST: GAUSSIAN The horizontal distribution of the release is Gaussian (normal).

12. GRID LENGTH: xx KM The horizontal grid length, in kilometres, used to run the model.

13. Indications related to the event itself for the release scenario. Can be UNCONFIRMED EVENT, IAEA CONFIRMED EVENT or TEST/EXERCISE.

14. EXISTENCE OR STRENGTH OF THE EVENT IS UNKNOWN This item is present when item 13 is UNCONFIRMED EVENT.

15. TOTAL RELEASE: 1.0E+00 BQ Radioactivity of the pollutant released is one Becquerel.

16. HEIGHT OF RELEASE: 0.0 METRE(S) Nominal height at which the pollutant is released.

17. VERTICAL DISTRIBUTION: UNIFORM 0-500 M Indicates the type of function that is used for the vertical distribution of the time release of the pollutant. In this case, the release is distributed uniformly in the first 500 metres above the model ground.

18. STANDARD DEVIATION (HOR): 1 GRID LENGTH Standard deviation used for the Gaussian function of the horizontal distribution (item 11). The grid length is given in item 12.

19. MAXIMUM CONCENTRATION AT O: Indicates the maximum value and its location on the map. Units are Bq·s/m3 for the 24 hours integrated surface concentration and Bq/m2 for total deposition. If the maximum concentration is in the vicinity of the source, it may be hidden by the X indicating the location of the source.

20. RESULTS BASED ON DEFAULT INITIAL VALUES This indicates that the default release scenario is used. It is based on a hypothetical source and no statement about the existence or strength of the event is implied by its use. In the case of an unconfirmed event, the existence and strength of the event are unknown.

21. Identification of the four concentration contours corresponding to powers of ten. Each contour is one hundredfold the previous contour. Note that the four concentrations contours may vary from one map to another. This is indicated on the maps by CONTOUR VALUES MAY CHANGE FROM CHART TO CHART. The units of the concentration are given in item 22.

22. Units of the concentration corresponding to items 5 and 21:

    • Bq·s/m3 for 24 hours integrated surface concentration;
    • Bq/m2 for total deposition.

Complete set of CANERM output maps for the default scenario

Figures 2 to 5 present a complete set of output maps for the default scenario. For these maps, the following items are identical:

(1):

The source site is PICKERING;

(2,3)

It is located at latitude 43 and 82/100 degrees North and at longitude 78 and 7/100 degrees West;

(4)

The release occurred at 15 UTC on 16 October 1995;

(7 to 22):

Defined here.

[View] (D)

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).

[View] (D)

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.

[View] (D)

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).

[View] (D)

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).

[View] (D)

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 information

Many 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 :

Michel Jean

Réal D'Amours

René Servranckx

The Green Lane^TM,
Environment Canada's World Wide Web Site.