A surprising answer to a hot question: controlled burns often fail to slow a bushfire



Firefighters conduct property protection as a bushfire approaches homes at Woodford NSW, Friday, November 8, 2019. Calls for more controlled burning are common after a major bushfire.
DAN HIMBRECHTS/AAP

Trent Penman, University of Melbourne; Kate Parkins, University of Melbourne, and Sarah McColl-Gausden, University of Melbourne

As sure as night follows day, this week’s bushfires prompted inevitable debate about whether fire authorities should have carried out more hazard reduction burning, and whether opposition from conservationists prevented this.

There are two key points to remember when we consider these questions. First, the impact on human life and property – not the impact on the environment – is the number one concern in the minds of fire officials when deciding whether to conduct a controlled burn. Second, and perhaps more importantly, evidence shows increasing the frequency or area of controlled burns does not necessarily reduce the bushfire risk.

In fact, during extreme fire danger conditions, reduced fuel loads – such as those achieved through hazard reduction burning – do little to moderate bushfire behaviour.

Firefighters protecting homes near Woodford, NSW as a bushfire approaches.
AAP

Officals under heat to cut fuel loads

Hazard reduction burning, also known as prescribed or controlled burning, is primarily used to prevent the spread of bushfires by reducing the build-up of flammable fuel loads such as leaf litter, grasses and shrubs.

Authorities routinely come under pressure to reduce bushfire fuel loads – especially in the wake of a bushfire crisis like the one seen on the east coast in recent days.

Media and mining magnate Kerry Stokes this week called for more controlled burning, saying this was a more pressing concern than climate change in dealing with bushfires.

And Nationals MP Barnaby Joyce reportedly lashed out at the Greens and others for purportedly opposing controlled burning and land clearing, claiming “there is all this bureaucracy that stands in the way of people keeping their place safe”.

The hazards of hazard reduction

Nationals MP Barnaby Joyce this week said ‘bureaucracy’ was getting in the way of rural landowners conducting hazard reduction on their properties.
Lukas Coch/AAP

Bushfire hazard reduction is not as simple as dropping a match indiscriminately and standing back to watch the landscape burn. Fire agencies must assess the risks and manage the potential impacts. These assessments are made in the years and months prior to the burn, as well as on the day.

Fire authorities invest significant time preparing for a controlled burn program. They work with communities to develop a plan and a rigorous process guides how, where and when the burns will be undertaken.

Protecting human life and property from the effects of a burn is the first priority, and by far represents the greatest challenge. Other impacts are also assessed in the process. These include effects on the environment, Indigenous and European cultural assets and sporting events.




Read more:
Mr Morrison, I lost my home to bushfire. Your thoughts and prayers are not enough


Despite extensive planning, over the past decade prescribed burns have escaped containment lines and destroyed houses, such as at Margaret River in Western Australia in 2013 and Lancefield, Victoria in 2015. To prevent a repeat of this, policies require burns only proceed when the weather is suitable not just on the day, but for three to five days afterwards. This has meant many burns do not go ahead or are delayed for years.

Smoke from fires can increase mortality and hospitalisation rates, and so the effect on human health is playing an increasing role in whether to burn or not. Viticulture concerns have also delayed burns because smoke can also destroy grapes used in wine production.

Thick smoke blankets Sydney Harbour in May 2019 after hazard reduction burns.
AAP

Controlled burns may not slow bushfires

Even if we were to carry out more controlled burns, it does not necessarily follow that bushfire risk would be reduced.

Controlled burns do not remove all fuels from an area. And forests accumulate fuel at different rates – some return to their pre-burn fuel loads in as few as three years.




Read more:
12 simple ways you can reduce bushfire risk to older homes


Our research has shown controlled burning was likely to have reduced the area later burnt by bushfires in only four of 30 regions examined in New South Wales, Victoria, South Australia and the ACT.

Evidence from a range of studies demonstrates fuel loads can significantly modify fire behaviour under benign weather conditions. But reduced fuel loads do little for bushfire mitigation under extreme fire weather and in times of drought.

A burnt-out structure on a property devastated by bushfires at Coutts Crossing in Northern NSW, November 2019.
Jason O’Brien/AAP

Looking to the future

Evidence is mounting of increased bushfire frequency and extent in both Australia and the US – a situation predicted to worsen under climate change. Changing weather patterns mean opportunities for controlled burning will likely diminish further. Coupled with expanding populations in high fire-risk areas, Australia’s fire agencies – among the best in the world – have a challenging time ahead.




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In future, we must think beyond traditional approaches to fire management. Acknowledging the role of climate change in altering natural hazards and the impact they have on humans and the environment is the first step. Communities should also be at the centre of decisions, so they understand and act on the risks.The Conversation

Trent Penman, Associate professor, University of Melbourne; Kate Parkins, Bushfire Risk Analyst, University of Melbourne, and Sarah McColl-Gausden, PhD student, University of Melbourne

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bushfires can make kids scared and anxious: here are 5 steps to help them cope


Toni Noble, Australian Catholic University

More than 600 schools have been closed, and some damaged, in recent days as bushfires rage across Queensland and New South Wales. Some students have been urgently evacuated while in school. People have lost homes and animals and are experiencing significant distress.

Research shows somewhere between 7% and 45% of children suffer depression after experiencing a natural disaster. Children more at risk of depression include those who were trapped during the event; experienced injury, fear, or bereavement; witnessed injury or death; and had poor social support.

The Victorian Education Department commissioned us after the 2009 Black Saturday fires to train teachers in seven fire-affected regions in methods to foster resilience in children.




Read more:
Mr Morrison, I lost my home to bushfire. Your thoughts and prayers are not enough


Teachers told us their students had experienced distressing emotions including high anxiety, fear and even panic during the event. Comments from teachers included:

Their world had changed forever; they became more fearful.

Some children were very frightened and for a long time stayed close to their parents.

Many children became scared and anxious about worldwide issues.

Their anxiety was triggered by the smell of smoke, a fire engine’s siren or a foggy day.

The teachers we interviewed also noted children’s profound sense of loss (of their homes, pets and livestock). Many students knew someone who had lost a family member or friend.

One teacher said:

The fires opened students’ eyes to what a disaster is. Not just something you see on TV.

We trained teachers using our Bounce Back program – a research-based social and emotional learning program first published in 2003. Most children are resilient and will bounce back quickly. Only a small minority may be at risk of ongoing anxiety and there are ways to minimise that risk.

How to help kids cope now

Try to stay calm and reassuring. Children take cues from the adults in their lives. If adults show fear and nervousness, children tend to mirror these emotions.

Try to focus on the small positives such as “we are all safe”. You can list the things that haven’t changed, such as your children’s friends. Reassure them other people such as family, friends, teachers and their community will help and that life will return to normal.

Everyone feels sad, anxious or upset when a bushfire burns near their home. By helping your child name their feeling, you are helping them feel more in control. Here are five steps to encourage your children to do this:

  1. take notice when your child is feeling sad, frightened, angry or upset
  2. encourage your child to talk about what’s troubling them, and listen and show you understand how they are feeling
  3. name the emotion in words your child can understand – are they “worried”, “scared”, “a bit frightened” or “sad”?
  4. help your child understand it’s normal to feel that strong emotion and help them to sit with their feelings
  5. finish with a hopeful or optimistic statement they can do something to help make things feel better. This may include something physical (such as going for a walk or throwing a basketball through a hoop), something that creates positive feelings (like playing with a pet or friend, or drawing), or doing something kind or helpful for someone else.

Resilience is the capacity to bounce back after hardship.

To help your child bounce back, you can communicate that:

  • life is mainly good but now and then everyone has a difficult or unhappy time
  • although things aren’t good now and it might take a while to improve, it’s important to stay hopeful and expect things to get better
  • you will feel better and have more ideas about what to do if you talk to someone you trust about what’s worrying or upsetting you
  • unhelpful thinking (“our family will never get a nice home again”) isn’t necessarily true and makes you feel worse
  • helpful thinking (“it might take a while to get our home back again but it will happen”) makes you feel better because it is more accurate and helps you work out what to do.



Read more:
Ignoring young people’s climate change fears is a recipe for anxiety


Coping after the event

Children with strong emotional support, such as from family and friends, are better able to cope with adversity.

Friendships may be disrupted after bushfires because of family relocations. Helping children connect via social media or phone with friends can reduce their sense of isolation.

Getting children back to school and regular routines can be one of the best ways to help their resilience.

Teachers are encouraged to allow time for children to talk about the bushfires and their feelings about them during class.

The teachers who participated in the Bounce Back program after Black Saturday explicitly taught children the skills for being optimistic and resilient – such as to challenge their unhelpful thinking and understand everybody, not just you, experiences setbacks sometimes.

They also taught kids skills for regulating their emotions and everyday courage to face their fears.

They used circle-time discussions of picture books and media stories to allow them to talk about their own experiences in a safe way.




Read more:
‘It’s real to them, so adults should listen’: what children want you to know to help them feel safe


We held focus groups with children of different ages in five of the primary schools that used our Bounce Back program. The children told us they: “know now what to do when something goes wrong”; “focus on more positives”; “don’t think the worst now”; “know things change”; “have learnt that sometimes you just have to put up with it”; and “now feel it’s easier to get back up in bad times”.

While a disaster can be challenging for children, a supportive home and school environment, together with coping skills, can help children recover reasonably quickly and get back to normal life.The Conversation

Toni Noble, Adjunct Professor, Institute for Positive Psychology & Education, Australian Catholic University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Grattan on Friday: When the firies call him out on climate change, Scott Morrison should listen


Michelle Grattan, University of Canberra

When five former fire chiefs held a news conference on Thursday to urge the federal government to take more action on climate change, it was a challenging moment for Scott Morrison.

Those who fronted the cameras represented a group of 21 men and two women, who make up the Emergency Leaders for Climate Action. These people have led fire and emergency services all around the nation.

They’re powerful voices, because they are advocates with compelling experience and expertise. The group’s messages are that we’re in “a new age of unprecedented bushfire danger”, climate change is the key reason why things are getting worse, and the government needs to respond with more resources and a better policy to reduce emissions and move to clean energy.

The problem is, as group founder Greg Mullins, former Fire and Rescue NSW commissioner, put it succinctly, “this government fundamentally doesn’t like talking about climate change”.

The devastating fires are a dramatic additional element intensifying the pressure on a government already increasingly on the back foot over climate change, as it responds poorly to a complex set of policy problems.

It’s not that Morrison denies climate change. It’s that he refuses to acknowledge it as a central issue, either because he doesn’t see it as such or because he fears provoking his right wingers.




Read more:
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Consider three factors now weighing on Morrison.

First, in Australia (as internationally) activism is rising. This should be broadly defined. Put aside the Extinction Rebellion, which may alienate more people than it persuades. Rather, include in the definition the many companies now factoring climate change into their planning, investment, and public statements.

Morrison might rail against activists hitting resource companies via secondary boycotts, and commentators might denounce so-called “woke” behaviour by business. But the long view indicates a tide is running here and its direction is clear.

Second, there is a general recognition the government’s climate policy is badly wanting. Emissions are rising. Its modest centrepiece – a fund paying for projects to reduce or capture emissions – isn’t doing the job. The fund’s limitations were tacitly acknowledged when recently the government set up a panel which sought submissions on how it could be enhanced.

More broadly, the government’s lack of a coherent energy policy means continued uncertainty for investors.

Third, Angus Taylor, minister for energy and emissions reduction, has frustrated those in the energy sector and the states. He’s too confrontational and short on people skills (in contrast to his predecessor Josh Frydenberg). His cheap shot accusing the Sydney City Council of ludicrous travel costs blew into a major embarrassment.

Next Friday Taylor will again be under scrutiny when he meets the states at the COAG energy council. The last meeting, nearly a year ago, turned into a nasty stoush between Taylor and the NSW minister.

If Taylor’s performance doesn’t improve in the next few months Morrison – who will be the one eventually carrying the can for policy failure – surely should move him. It would be interesting to see how (say) a Simon Birmingham or a Mathias Cormann would go in the portfolio. Better, you’d think.




Read more:
‘Like volcanoes on the ranges’: how Australian bushfire writing has changed with the climate


It was no wonder Morrison wanted to contain partisan argument while the fires rage. It’s a reasonable view for a prime minister to take, with a basis in past practice, but was also politically driven.

Morrison has been assisted in this by Labor, despite the ALP recently voting in parliament (without success) for a “climate emergency” to be declared. Anthony Albanese believed there was no gain in seeking to score points during a disaster, and danger in doing so.

But a moratorium, although mostly adhered to by Liberal and ALP federal politicians, was never going to happen more generally. Indeed some people, like the retired fire chiefs, judged this was precisely the moment to press their point.

It was predictable the Greens would strike hard; climate is core ground for them. But that Deputy Prime Minister Michael McCormack would take the bait, leaping in to condemn “the ravings of some pure enlightened and woke capital city greenies”, showed a lack of discipline, probably in part a reflection of the strain the Nationals leader is under as he tries to manage a difficult party room.

Some believed McCormack was playing to his base. If so, he’d only be talking to part of it, most notably those with an eye to the coal industry. Many farmers are very aware, first hand, of the impact of the changing climate.

After its election loss, there’s been much talk about how Labor is caught between its dual constituencies on climate – inner city progressives versus traditional suburban workers.

But the Liberals face their own dilemma, which could deepen as the issue amps up in the electorate. We have seen over many years the split within the Liberal party, and the very high costs it has extracted. As Morrison assesses how to pitch to voters in the future, he might have to be careful of straining internal unity.




Read more:
Firestorms and flaming tornadoes: how bushfires create their own ferocious weather systems


Over coming months, the fires’ impact on public opinion will presumably be measured in the focus groups through which the government hears its “quiet Australians”.

More immediately, Morrison won’t be able to escape a response when this crisis passes. His moratorium will make expectations greater.

John Connor was formerly CEO of the now defunct Climate Institute, which commissioned from the CSIRO a 2007 research paper – that turned out to be prescient – on the link between climate and bushfires, titled Bushfire Weather in Southeast Australia: Recent Trends and Projected Climate Change Impacts.

Connor, who now heads the Carbon Market Institute (which describes itself as a peak industry body for climate action and business) suggests the current situation provides the opportunity for an “armistice” – a chance to build a platform on the middle ground for the climate debate.

One step, Connor says, would be for the government to establish a parliamentary inquiry to examine the growing risk climate change presents for the fire scene and the resources required for the future.

“It could be a stepping stone to a more mature debate about carbon policy for the broader economy,” Connor says, although he admits “I’m a professional optimist”.

The government’s former drought co-ordinator, Stephen Day, wrote in his report, finally released last week: “As a consequence of climate change drought is likely to be more regular, longer in duration, and broader in area”.

What’s striking about Day’s observation is how matter-of-fact it is. Climate change is stated as a reality from which other considerations flow. The same reality applies to bushfires. It also applies to the need to move the economy to a new energy mix and net zero emissions by 2050.The Conversation

Michelle Grattan, Professorial Fellow, University of Canberra

This article is republished from The Conversation under a Creative Commons license. Read the original article.

12 simple ways you can reduce bushfire risk to older homes



There are no guarantees in bushfires, but you can improve the odds your house survives a blaze.
Photo by Edward Doody, courtesy of Arkin Tilt Architects, Author provided

Douglas Brown, Western Sydney University

Seventy-five years of Australian research into how houses respond to bushfire has identified 21 main weak points in houses and the area immediately surrounding them.

In recent decades this knowledge has been used to inform new building construction. But older houses are generally not built to the same standard, unless they have been significantly renovated.

Older homes make up the majority of buildings in bushfire prone-areas. There are some simple things that can improve the performance of an older house in a bushfire. Here are 12 suggestions: six simple projects that could be done over a weekend or two, and six low-cost things you could do in a single afternoon.




Read more:
Where to take refuge in your home during a bushfire


Six weekend projects:

1. Remove some garden beds next to the house

This is particularly true for garden beds near timber-framed windows and doors. For timber and fibro homes, garden beds adjacent to the house should be avoided entirely. At the very least prune dense bushes close to timber-framed windows back hard.

2. Sand and repaint weathered timber door and window frames

Over time, paint peels and cracks appear in the exposed and weathered timber. During a bushfire, embers can lodge in these cracks and ignite.

3. Enclose the subfloor with a metal mesh

Flammable items are often stored underneath the house. If this area is not enclosed these items will catch, often due to ember attack, and pose a threat to every room in the house. The exposed underside of timber floors can be protected with a lightweight, non-combustible layer.




Read more:
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4. Repair or replace weathered timber decking

Just as embers can land in cracks in door and window frames, the same can also happen to weathered timber decking. Most decks are right next to the house and if they go up fire easily spreads to the home.

5. Have a 1-2 metre non-flammable area immediately around your house

Think of it as an additional protective defence area. You could use gravel, paving tiles, bricks, concrete, or ground rock such as scoria.

6. Get a professional roof inspection

Roofs gradually weaken and require maintenance. A professional roof repairer can check that tiles are in place, repair damaged ridge tiles, and ensure that skylights, air vents, evaporative coolers, and solar panels are in good order and are free from gaps where embers could enter.

The product specifications for timber door and window frames, metal mesh, and decking materials can be found in the relevant Australian Standard and steel construction standard. Actual requirements for houses vary according to the bushfire attack level associated with a specific block of land.

Open sub floor spaces are vulnerable, especially if used to store flammable material.
Douglas Brown, Author provided

Six easy afternoon projects

1. Replace natural coil doormats with synthetic

While they appear harmless, natural organic doormats can cause a fire to grow if they ignite. Due to their density they burn for a long time, and can spread flames to timber door frames. A synthetic mat will only flare up for a short time.

2. Remove organic mulch from garden beds next to the house

Burning embers can easily ignite dried-out organic mulch, setting fire to surrounding plants. If garden beds are near the house, particularly timber door and window frames, the danger is increased. Either remove mulch in garden beds next to the house or – if the mulch is suitable – dig it in deeply.

3. Store firewood in an enclosed metal container

It is best to store wood well away from the house, but no one wants to walk metres in cold winters to get that wood. So some firewood is often stored close to the house on a burnable deck, and often it’s left there over summer. Putting it into a large metal container can remove that fire risk.

4. Remove flammable material from the front porch, roof cavity, decking and underfloor area

When embers enter the roof cavity and underneath the house, flames can rapidly spread to every room. It is vital to keep these areas clear of flammable materials.

5. Replace timber benches on timber decks with synthetic ones

A timber bench on a timber deck next to a timber house is an unnecessary risk, similar to having a wood pile on a timber deck.

6. Turn pressure relief valves on outside gas bottles away from the house

Both the 2003 Canberra and the 2016 Wye River bushfires showed the danger of having gas bottle valves facing the house. In both fires, houses were destroyed when either the gas plume flamed or gas bottles exploded.

While these projects will improve the bushfire protection of your home, they can’t guarantee your home will survive a bushfire, especially during catastrophic bushfire conditions. It is also crucial to upgrade your home insurance so you can meet the higher costs of new building standards, in the event you have to rebuild. And in all cases, act on warnings given by your state or territory fire authority.


The advice given in this article is general and may not suit every circumstance.The Conversation

Douglas Brown, Casual Academic, Western Sydney University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

As flames encroach, those at risk may lose phone signal when they need it most


Stanley Shanapinda, La Trobe University

Yesterday, New South Wales and Queensland issued fire warnings classified as either “catastrophic”, “severe” or “extreme” – and these conditions will remain in the coming days.

The Bureau of Meteorology’s fire danger rating for Wednesday, November 13.
RFS QLD

Areas under threat include the greater Sydney area, northern New South Wales, the Northern Goldfields, and the Central Highlands. The declared state of emergency means human life is at great risk.

Those at risk should evacuate ahead of time, as mobile phone services may not be reliable when needed the most.

Service outages

People in dangerous bushfire situations often have the added burden of service outages. This can happen following fire damage to infrastructure (such as signal towers) that connects base stations that relay communications within the network. A break in this connection means no signal, or weak signal, for those on the ground.

Generally, radio waves used for mobile communication behave differently as they travel, based on various factors that affect signal strength. One factor is land geography, such as the height of hills. The signal may not be able to penetrate sand hills. Gum trees may also reflect, obstruct and absorb radio signals.




Read more:
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The scenarios described above can be made worse by fire environments, based on the frequencies used. Flames can produce “plasma”, which reacts with the surrounding magnetic field, and this degrades signal strength.

Rural fire service operations may use frequencies in the 400-450MHz range to communicate, but these signals are weakened during fire, in which case they may use frequencies in the 100-180MHz range. At this wavelength, signal strength doesn’t degrade as badly and can sustain better communication.

Being far away from a mobile phone tower, often in rural areas, also results in degraded communication. Rural areas don’t receive as much coverage because installing cell towers in these areas is not particularly profitable, and towers are built based on revenue estimates. There is little incentive to build networks with additional capacity in rural areas.

Get out while you can

In bushfire situations, it’s crucial to leave affected areas early to avoid becoming stuck in mobile black spots. These are regional and remote areas that have been identified as not having mobile phone coverage.

Some mobile black spots where fire danger warnings have been issued include Mount Seaview and Yarras, not far from the Oxley Highway in NSW. The status of the fires there was reported “out of control” on Tuesday morning.




Read more:
What has Australia learned from Black Saturday?


Optus is planning to roll out macrocells at these locations to expand coverage between the end of this year and the middle of next year. These are base stations that cover a wide area and are typically deployed in rural regions or along highways.

Until the macrocells are deployed, people living in mobile black spots, or who may be forced to pass through these areas due to fire, continue to be at risk. When passing through a fire-affected black spot, you are virtually unreachable.

Also, although the mobile black spot program will help to increase 4G coverage in rural areas, most rural areas, including many at high risk of bushfires, rely largely on 3G. When people need extra data capacity during emergencies, the network is incapable of handling the increased traffic load, as every device is trying to connect and download data at the minimum 3G capacity of 550Kbps.

Network overload

The network gets congested at times of catastrophe due to the high volume of mobile phone traffic experienced, which exceeds the available network capacity. The mobile network in Billy’s Creek in NSW, and the areas connected to it, experienced an outage yesterday.

Telstra’s services have also been affected. As of Monday, people in Billy’s Creek, Yarras and Nimbin (among other locations) were unable to send or receive messages, make calls or access the internet, and may not have been up to date with the latest fire information, unless through radio or television.

During bushfires last year, for every three calls attempted under Telstra’s network, one was eventually answered. Everyone trying to call at once is referred to as a “mass call event”. This creates “congestive collapse” in parts of the internet-based network, blocking new connections from being made.

During congestion, the performance of the network decreases because the internet packets that carry the calls or messages are dropped, or delayed, before they reach their destination. One solution is for operators to have signal boosters installed for the affected part of the network.

There’s an app for that, if you have good connection

In the same way, the “Fires Near Me Australia” web application is likely to suffer from internet packet deliveries being delayed.

The app may be overwhelmed if too many people try to access it at once, and may crash. In such scenarios, people should reboot their phones and keep trying to connect.

Some people have made complaints of not being able to download the app, and others of the app crashing, because their phone’s model was not new enough to support it.

If the fires spread to densely populated areas, available 4G capacities may be exhausted by the sheer volume of the traffic. And congestion is made worse by more incoming traffic from across the country, from concerned family and friends.

Preventative measures may no longer be an option for many. But in the future, people in fire-prone areas may benefit from buying a personal 4G or 3G mobile signal booster ahead of time.




Read more:
How to keep your mobile phone connected when the network is down


The Conversation


Stanley Shanapinda, Research Fellow, La Trobe University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Australia: Climate of Denial and Warnings Ignored


The link below is to yet another article dealing with bushfires and the denial of climate change.

For more visit:
https://www.theguardian.com/australia-news/2019/nov/14/former-australian-fire-chiefs-say-coalition-doesnt-like-talking-about-climate-change

Firestorms and flaming tornadoes: how bushfires create their own ferocious weather systems



A firestorm on Mirror Plateaun Yellowstone Park, 1988.
Jim Peaco/US National Park Service

Rachel Badlan, UNSW

As the east coast bushfire crisis unfolds, New South Wales Premier Gladys Berejiklian and Rural Fire Service operational officer Brett Taylor have each warned residents bushfires can create their own weather systems.

This is not just a figure of speech or a general warning about the unpredictability of intense fires. Bushfires genuinely can create their own weather systems: a phenomenon known variously as firestorms, pyroclouds or, in meteorology-speak, pyrocumulonimbus.




Read more:
Firestorms: the bushfire/thunderstorm hybrids we urgently need to understand


The occurrence of firestorms is increasing in Australia; there have been more than 50 in the period 2001-18. During a six-week period earlier this year, 18 confirmed pyrocumulonimbus formed, mainly over the Victorian High Country.

A pyrocumulonimbus cloud generated by a bushfire in Licola,Victoria, on March 2, 2019.
Elliot Leventhal, Author provided

Its not clear whether the current bushfires will spawn any firestorms. But with the frequency of extreme fires set to increase due to hotter and drier conditions, it’s worth taking a closer look at how firestorms happen, and what effects they produce.

What is a firestorm?

The term “firestorm” is a contraction of “fire thunderstorm”. In simple terms, they are thunderstorms generated by the heat from a bushfire.

In stark contrast to typical bushfires, which are relatively easy to predict and are driven by the prevailing wind, firestorms tend to form above unusually large and intense fires.

If a fire encompasses a large enough area (called “deep flaming”), the upward movement of hot air can cause the fire to interact with the atmosphere above it, potentially forming a pyrocloud. This consists of smoke and ash in the smoke plume, and water vapour in the cloud above.

If the conditions are not too severe, the fire may produce a cloud called a pyrocumulus, which is simply a cloud that forms over the fire. These are typically benign and do not affect conditions on the ground.

But if the fire is particularly large or intense, or if the atmosphere above it is unstable, this process can give birth to a pyrocumulonimbus – and that is an entirely more malevolent beast.

What effects do firestorms produce?

A pyrocumulonibus cloud is much like a normal thunderstorm that forms on a hot summer’s day. The crucial difference here is that this upward movement is caused by the heat from the fire, rather than simply heat radiating from the ground.

Conventional thunderclouds and pyrocumulonimbus share similar characteristics. Both form an anvil-shaped cloud that extends high into the troposphere (the lower 10-15km of the atmosphere) and may even reach into the stratosphere beyond.

NASA image of pyrocumulonimbus formation in Argentina, January 2018.
NASA

The weather underneath these clouds can be fierce. As the cloud forms, the circulating air creates strong winds with dangerous, erratic “downbursts” – vertical blasts of air that hit the ground and scatter in all directions.

In the case of a pyrocumulonimbus, these downbursts have the added effect of bringing dry air down to the surface beneath the fire. The swirling winds can also carry embers over huge distances. Ember attack has been identified as the main cause of property loss in bushfires, and the unpredictable downbursts make it impossible to determine which direction the wind will blow across the ground. The wind direction may suddenly change, catching people off guard.

Firestorms also produce dry lightning, potentially sparking new fires, which may then merge or coalesce into a larger flaming zone.

In rare cases, a firestorm can even morph into a “fire tornado”. This is formed from the rotating winds in the convective column of a pyrocumulonimbus. They are attached to the firestorm and can therefore lift off the ground.




Read more:
Turn and burn: the strange world of fire tornadoes


This happened during the infamous January 2003 Canberra bushfires, when a pyrotornado tore a path near Mount Arawang in the suburb of Kambah.

A fire tornado in Kambah, Canberra, 2003 (contains strong language).

Understandably, firestorms are the most dangerous and unpredictable manifestations of a bushfire, and are impossible to suppress or control. As such, it is vital to evacuate these areas early, to avoid sending fire personnel into extremely dangerous areas.

The challenge is to identify the triggers that cause fires to develop into firestorms. Our research at UNSW, in collaboration with fire agencies, has made considerable progress in identifying these factors. They include “eruptive fire behaviour”, where instead of a steady rate of fire spread, once a fire interacts with a slope, the plume may attach to the ground and rapidly accelerate up the hill.

Another process, called “vorticity-driven lateral spread”, has also been recognised as a good indicator of potential fire blow-up. This occurs when a fire spreads laterally along a ridge line instead of following the direction of the wind.

Although further refinement is still needed, this kind of knowledge could greatly improve decision-making processes on when and where to deploy on-ground fire crews, and when to evacuate before the situation turns deadly.The Conversation

Rachel Badlan, Postdoctoral Researcher, Atmospheric Dynamics, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.