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Bushfires affect the surrounding atmosphere because of the large amount of heat and moisture released as a result of combustion. The atmospheric response to this energy input includes changes to the local winds, modification of the boundary layer, and the development of pyroconvective clouds. These changes can profoundly modify the evolution of the fire. This project is:
- Developing an Australian coupled fire-atmosphere modelling capability based upon the national numerical weather prediction infrastructure.
- Developing a better understanding the contribution of fire-atmosphere interaction and three-dimensional atmospheric structure to fire behaviour, including spread, intensification, and ‘low-up’ behaviour.
- Developing a better understanding the impact of fire on the atmosphere, including fire-generated winds and their damage potential, ember transport and plume development.
- Progressing towards an eventual operational capability for coupled fire-atmosphere modelling within Australia.
- Improving operational fire prediction services by efficiently transferring the knowledge gained in this project and others to fire weather forecasters and to fire behaviour analysts.
- Exploring the development of computationally efficient methods for robustly accounting for fire-atmosphere coupling in fire prediction.
The project uses the premier operational Australian high-resolution weather prediction model, the Australian Community Climate and Earth-System Simulator (ACCESS), coupled to a fire spread model.
The coupled fire-atmosphere model ACCESS-Fire will be installed on national Australian computing infrastructure for research application, with future capability for operational use. The model will be used to run a series of case studies. Detailed examination of high impact events and verification against available meteorological and fire behaviour data will highlight the importance of assessing and predicting the likelihood of fire-atmosphere interactions in anticipating fire evolution. The close links of the project team with operational and training activities will provide a clear pathway for implementing research findings.
The January 2016 Waroona bushfire in Western Australia has been selected as the first case study to test the model. Over a two-day period, there were two separate pyro-convective thunderstorms, triggered by different processes during the diurnal cycle. In addition, analysis of Doppler radar data shows detail of the rapid plume development that contributed to the ember shower which burnt Yarloop, causing two fatalities.
This research into interactions with topography, potential for pyro-convection, potential for three dimensional interactions, potential for winds to change substantially around a fire, water vapour dry slots, plume development and spotting process will be integrated into a formal, quantitative system for use with the current fire forecasting system.
|2016||Report||Coupled fire-atmosphere modelling: Annual project report 2015-2016. (Bushfire and Natural Hazards CRC, 2016).|
|2015||Presentation||Coupled Fire-Atmosphere Modelling. (2015).|
In January 2015, the Sampson flat bushfire burnt in the Adelaide hills. it was active for 6 days, burning 12,500 ha, 27 homes, numerous sheds and 900 animals. This study focuses on the meteorological conditions on the day of ignition Friday 2 January. the major fire run occurred the following day.
Coupled fire-atmosphere models show three-dimensional interactions between a fire and the surrounding atmosphere.
Some bushfires exhibit extreme behaviour that exceeds the bounds of existing predictive guides. Coupling between the fire and the atmosphere has been invoked as a cause of such unexpected behaviour. Events of this type are uncommon and cannot be investigated by conventional field experiments. This modelling project allows complex interactions between a fire and the atmosphere to be studied, potentially providing physically-based explanations that will lead to more reliable predictions and reduced risk to firefighters and the community.