The Kangaroo Island bushfires of 2007 a meteorological case study and WRF-fire simulation

Abstract

In December 2007, Kangaroo Island was set ablaze by numerous dry lightning strikes. Our research into the event has been conducted in two parts; a case study investigating the interactions between the local meteorology and observed fire behaviour, followed by simulations using the coupled atmospheric-fire behaviour model WRF-fire. The findings from the case study highlight the importance of including information on atmospheric instability and spatial variation in meteorological parameters in fire weather forecasts. Our preliminary simulations using WRF-fire have explored the ability of the model to capture phenomena observed in the case study. The case study identified two occurrences of unusual fire behaviour which have been simulated: the first, when a fire located in a local sea breeze front convergence zone produced a spectacular convection column which developed by release of potential atmospheric instability triggered by local lifting; the second, when unprecedented fire behaviour was observed in relatively benign conditions, hypothesised to be due to convective plume entrainment of dry air aloft, enhanced by topographically driven processes and very dry, open structured fuels. The circumstances leading to the unusual fire behaviour(s) illustrate known limitations in the current Australian approach to fire weather forecasting, which neglects temporal and spatial variations, three dimensional atmospheric evolution and any interaction of the fire with the atmosphere. We used the coupled atmosphere-fire model WRF-fire to simulate the fires, with the initial aim of running WRF-fire on an Australian event and subsequently to assess the ability of WRF-fire to simulate the vertical dynamics and fire-atmosphere coupling observed in the case studies.