Understanding extreme bushfire behaviour and firestorm development

Funded through several Discovery Indigenous scheme grants, Bundjalung man and Professor in the School of Science at UNSW Canberra, Professor Jason Sharples, has led research into understanding extreme and dynamic fire behaviour, and predicting firestorm events.

Professor Sharples says that extreme wildfires are fires that exhibit deep or widespread flaming in unstable atmospheric conditions, which are conducive to the development of towering fire clouds known as pyrocumulus or pyrocumulonimbus storms.

Using mathematical models, he has identified several different factors which influence whether deep flaming will occur. Deep flaming can be triggered by strong winds, winds changing direction, fire eruption, lateral spread of fire across the wind (rather than only in the direction of wind), overzealous backburning, mass spotting, fire line merging or a combination of these factors.

The research has also demonstrated that rugged terrain is a key contributing factor. Interactions between the fire and the atmosphere over rugged, forested landscapes can result in highly atypical and dangerous patterns of fire spread, with abrupt increases in fire intensity and fires moving in unexpected directions.

The ‘blow-up fire outlook model’ developed by Professor Sharples and his colleagues condenses these findings into a predictive tool for fire mangers. It integrates the various factors that contribute to deep flaming with measures of atmospheric instability to determine the likelihood of a fire developing into a firestorm.

	THE OCCURRENCE OF FIRESTORMS APPEARS TO BE INCREASING IN FREQUENCY AROUND THE WORLD AND MODELS LIKE THE ‘BLOW-UP FIRE OUTLOOK MODEL’ WILL ASSIST AUTHORITIES IN FACING THESE UNPREDICTABLE PHENOMENA.

 

Image: 2013 Grampians Fire, Victoria, exhibiting a toweri cloud or ‘pyrocumulonimbus’. Credit: Randall Bacon.