Factors influencing the development of violent pyroconvection. Part I: fire size and stability
Rachel L. Badlan A F , Jason J. Sharples A D E , Jason P. Evans B and Rick H. D. McRae C
+ Author Affiliations
- Author Affiliations
A School of Science, University of New South Wales, Canberra, ACT 2600, Australia.
B Climate Change Research Centre, University of New South Wales, Kensington, NSW 2052, Australia.
C Australian Capital Territory Emergency Services Agency, Canberra, ACT 2601, Australia.
D Bushfire and Natural Hazards Cooperative Research Centre, East Melbourne, Vic. 3002, Australia.
E ARC Centre of Excellence for Climate Extremes, UNSW Canberra, ACT 2600, Australia.
F Corresponding author. Email: rachel.badlan@gmail.com
International Journal of Wildland Fire 30(7) 484-497 https://doi.org/10.1071/WF20040
Submitted: 26 March 2020 Accepted: 20 April 2021 Published: 21 May 2021
Abstract
Violent fire-driven convection can manifest as towering pyrocumulus (pyroCu) or pyrocumulonimbus (pyroCb) clouds, which can have devastating impacts on the environment and society. Their associated fire spread is erratic, unpredictable and not generally suppressible. Research into large pyroconvective events has mainly focused on the atmospheric processes involved in normal atmospheric convection, or on surface fire weather and associated fuel conditions. There has been comparatively less attention paid to the role of the fire itself in these coupled fire–atmosphere events. This paper draws on recent insights into dynamic fire propagation and extreme wildfire development to investigate how the fire influences the occurrence of violent pyroconvective events. A static heat source of variable dimension and intensity is used. This is accompanied by a companion paper that extends the analysis by including the effect of fire geometry on the pyroconvective plume. The analyses indicate that the spatial expanse and intensity of large fires are critical factors driving the development of pyroconvective plumes and can override the influence of the stability of the atmosphere. These findings provide motivation for further investigation into the effect of the fire’s attributes on the immediate atmosphere and have the potential to improve forecasting of blow-up fire events.
Keywords: deep flaming, fire–atmosphere interaction, pyroconvection, pyrocumulonimbus, wildfire modelling.
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