Fire-atmosphere coupled numerical simulations show a fire changes the local meteorology
This is a paper presented at the 2013 Bushfire CRC Research Forum.
The idea that a fire ‘creates its own weather’ is supported by observations from fire grounds and results from idealised numerical simulations. We have simulated two Australian bushfires where unexpected fire behaviour occurred, using the coupled fireatmosphere model WRF-fire. The results present new evidence of dynamical interactions between a fire and the surrounding atmosphere. The simulations are of two fires that burnt on Kangaroo Island, South Australia in December 2007, the D’Estrees fire and the Rocky River fire. In the D’Estrees simulations, fire-atmosphere interactions produced a long-lived fire-induced vortex. In the Rocky River simulations, fire perimeter was sensitive to the local fire-modified winds that arise from interactions between the fire, atmosphere and local topography. A simulation of the Rocky River fire at high temporal resolution produced pulses in the rate of spread of the fire front coincident with the passage of mesoscale convective cells. The simulation results suggest that the potential for extreme fire behaviour arises from interactions between the fire and the atmosphere. These results add to the body of research showing that feedback between a fire and the atmosphere can play an important role in shaping both fire behaviour and micro-scale meteorology. As a consequence, we affirm that a comprehensive risk assessment at a fire-ground should consider the three-dimensional structure of the atmosphere and the possibility of dynamical feedback processes occurring.