Dispersion modelling at Met Éireann
A new decision support system is being provided by Met Éireann to provide guidance in emergencies related to the dispersion of hazardous materials in the atmosphere. The system provides a tailored service to users in the Environment Protection Agency (EPA), the Radiological Protection Institute of Ireland (RPII, currently merging with the EPA) and the Department of Agriculture, Food & the Marine (DAFM). The system enables staff to track and forecast the movement of materials in the atmosphere, including their interaction with the environment. For DAFM the system is primarily aimed at predicting the movement of Foot & Mouth virus particles in the event of an outbreak of the disease. The system will be used by the EPA in the event of emergencies related to chemical spillages, large fires or distant volcanic eruptions that might compromise air quality over Ireland. Likewise, the RPII will use the system for guidance on the dispersion of radioactive materials released into the atmosphere.
At its core, the system uses the US NOAA HYSPLIT atmospheric dispersion model, extensively modified by Met Éireann researchers to accommodate the special requirements of the EPA/RPII and DAFM. Atmospheric forecast and analysis fields are used to drive the model and provide estimates of atmospheric concentrations of the material allowing for effects such as deposition and interactions with moisture/rainfall.
The user-friendly system is designed so that the latest weather information is always available to provide the most up-to-date information in an emergency. For example, in the event of a Foot & Mouth outbreak the weather data from Met Éireann's operational numerical weather forecast system are automatically available over the past 30 days to provide information on the past evolution of the virus while the latest forecasts provide information on the future movement; all data are at the native resolution of the forecast system and are automatically updated as new forecasts are produced. The system is run in a secure environment at the Irish Centre for High-End Computing (ICHEC). Tracking the movement of radioactive material in the atmosphere over the global scale is likewise supported through use of the latest European Centre for Medium-Range Weather Forecasts (ECMWF) global analyses/forecasts.
Met Éireann maintains the system and provides general support for the users.
An example of the use of the system: Mercaptan gas plume
During an incident in January 2013 a large quantity of Mercaptan gas (the gas used to give natural gas a bad odour) was accidentally released by a factory in northern France. Although of no major health concern to the public, the smell of 'rotten eggs' could be smelt over large distances. The animation above shows how the gas plume likely dispersed in the lower atmosphere. Areas in red or orange were likely to experience traces of a bad odour. The concentration of the gas was not high enough to be smelt by the time the plume reached Ireland, 2 days after its initial release.