Improving the scalability of an emergency response model The UK Met Office’s NAME model can simulate the progress of billions of particles through the global atmosphere, but requires major computing resources to do so. Thanks to work by EPCC, NAME can now run on large parallel systems and promises more accurate forecasts of hazards. Early on 26th April 1986, Reactor Number 4 at Chernobyl – in what is now Ukraine – suffered a catastrophic failure, causing the release of a large radioactive plume into the atmosphere. Weather conditions at the time caused the contents of the plume to be swept over north-western USSR, and towards Scandinavia and other parts of northern Europe. This resulted in widespread public health concerns, particularly in upland areas where high rainfall led to significant accumulation of radioactive isotopes such as iodine and caesium on farmland and hence in grazing animals. One further result of the Chernobyl disaster was the development of what was then referred to as the “Nuclear Accident Model” at the Met Office. Originally intended to simulate the dispersion of radioactive species, interests have expanded to include routine air quality forecasting, and predicting the spread of pollutants, airborne viruses and volcanic ash. Notable occasions when the model has been brought into operational use include the outbreak of foot-and14
mouth disease in the UK in 2001, the eruption of Eyjafjallajökull and the consequent disruption to commercial air traffic in April 2010, and during the Fukushima nuclear power station disaster following the tsunami in Japan in 2011. This widening of the scope of interest has meant the model has been renamed Numerical Atmospheric dispersion Modelling Environment (NAME)1. NAME is a “Lagrangian” model which represents atmospheric dispersion by tracking simulated ‘particles’. Movement through the atmosphere is typically driven by numerical weather prediction data (either historical data or operational forecast) while particles also undergo a random motion to represent small-scale turbulence which is not resolved. Particles are generated by a specified source or set of sources which may be natural (eg a volcano or a fire) or man-made (eg a factory or other known source of pollution). Particles may be removed from the atmosphere by a number of different processes such as fall-out
Kevin Stratford EPCC Software Architect k.stratford@epcc.ed.ac.uk Ben Devenish UK Met Office ben.devenish@metoffice.gov.uk
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