In a world-first, scientists from New Zealand’s Scion, the US Forest Service, the University of Canterbury’s School of Earth, and Environment and the US National Centre of Atmospheric Research have successfully generated fire whirls on slash piles near Twizel.
The activity is part of new research to protect firefighters and communities from the devastating impact of future wildfire events.
Fire whirls/vortices, or fire tornados, occur during extreme wildfire events around the world, but until this month, they have never been deliberately created in the field and at this scale.
- View the footage of the experiment here.
The research, funded by the NZ Ministry of Business, Innovation and Employment (MBIE), aims to strengthen defences against the devastating impact of wildfire.
Fire whirls emerge spontaneously during extreme wildfire events, but their deliberate inception in an open field and at such a scale has not been previously attempted.
Leading expert on wildfire vortices, Jason Forthofer, is a leading expert on wildfire vortices who has been studying fire whirls in a laboratory environment.
“Instigating a fire vortex outside a laboratory environment is unprecedented at this scale and with forest fuels across the globe.”
Isolating fire whirls and metrological modelling
According to Shana Gross, the lead scientist at Scion, the experiments aimed to isolate the fire whirls that occur outside of wildfires and investigate the factors responsible for their formation.
“Our experiments were designed to isolate and scrutinise the genesis of fire whirls, enabling us to detect ‘red flags’ for firefighters indicating an impending fire whirl.”
Shana Gross told the Timaru Herald that the experimental burns on private land north of Twizel were part of a five-year research programme building on the past 28 years of rural fire research in New Zealand.
The test occurred not on land involved in the devastating 2020 fires at Lake Ōhau and Lake Pukaki-Aoraki/Mt Cook but were “indirectly related … in the sense that those fires were in wilding pines and that there are a lot of wildings in the area”.
“The location was selected because it had standing wildings, down piled wildings, and is flat.
“Extreme fires are difficult to predict and behave erratically. They exhibit hard-to-control fire behaviours such as fire whirls, spotting and rapid fire spread.”
Associate Professor Marwan Katurji, specialising in Atmospheric Dynamics at the University of Canterbury, highlighted the significant implications of their research:
“Studying the thermal column enveloping the fire vortex will allow us to fine-tune fire behaviour and fire scale meteorological models. These models will yield essential spatial data to understand the physical processes governing the emergence and behaviour of these hazardous fire whirls.”
Scion’s alliance with Fire and Emergency New Zealand (FENZ) was crucial in successfully implementing this research, with FENZ providing operational support during fieldwork.
The research methodology
A group of 24 scientists conducted a four-day project that involved igniting nine wilding pine slash piles of different sizes. During the research trials, one of the piles, which measured 20 meters in diameter, resulted in a ‘smoke devil’ and fire whirl that lasted the longest.
To monitor, measure, and analyze the fire whirls, the researchers used specialized equipment worth over NZ$1 million. This equipment included high-speed thermal infrared cameras, visual cameras, Unmanned Aerial Vehicles (UAVs), and meteorological heli-kites. The data collected included the temperature within the fire whirl, the inward wind flow, and atmospheric conditions within and outside the fire environment.
The experiments took place on privately owned land located north of Twizel, where four sets of wilding pine slash piles were established over the past year. The first burn occurred on May 2, followed by three others on different days.
The team observed that the smoke plume rose before the vortex formed, even with low-intensity fires, which could hold in varying conditions. The researchers plan to analyze the data collected over the next several months
.Hugh Wallace, who is the research lead at SCION, expressed his gratitude for the valuable data that has been collected. He also noted that each experiment conducted has helped the team understand the nuances of the factors that lead to fire whirls in forest debris and wilding pines.
UN: 50% increase in global wildfires by 2100
Wildfires worldwide are on the rise, impacting both rural and urban areas.
In 2020, New Zealand’s economy suffered a direct cost of $142 million due to wildfires. Experts predict that this figure will increase to $547 million annually by 2050, largely due to the effects of climate change.
In a UN report published in February 2020, climate change and land-use change are projected to make wildfires more frequent and intense.
In a report published by the UN Environment Programme (UNEP) and GRID-Arendal, a global increase of extreme fires of up to 14 per cent by 2030, 30 per cent by the end of 2050 and 50 per cent by the end of the century.
According to Forthofer, it is difficult to study fire whirls in a running vegetation fire due to the limited knowledge of what causes their formation, despite the increasing number of fire whirls being documented worldwide.
“Improving firefighter safety is always a top priority. This research can help by making it easier for firefighters to see when the conditions are right for a vortex to form.”
“By isolating the whirls into large pile burns we could control the location and timing of the whirl. Augmenting lab data with field experiments is important as elements such as changing weather, including wind, are not accounted for in the lab.”
This year’s activity is part of the Scion-led Extreme Wildfire Research Programme that runs through until early 2026.