tag:theconversation.com,2011:/institutions/act-emergency-services-agency-1163/articlesACT Emergency Services Agency2019-11-20T03:45:03Ztag:theconversation.com,2011:article/1272252019-11-20T03:45:03Z2019-11-20T03:45:03ZClimate change will make fire storms more likely in southeastern Australia<p>Temperatures across many regions of Australia are set to exceed 40°C this week, including <a href="http://www.bom.gov.au/australia/heatwave/#heatwave-forecasts">heatwaves</a> forecast throughout parts of eastern Australia, raising the spectre of more devastating bushfires.</p>
<p>We have already heard <a href="https://www.canberratimes.com.au/story/6486857/nsw-fire-emergency-what-all-the-terms-mean/">warnings</a> this fire season of the possibility of firestorms, created when extreme fires in the right conditions form their own weather systems. </p>
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Read more:
<a href="https://theconversation.com/firestorms-and-flaming-tornadoes-how-bushfires-create-their-own-ferocious-weather-systems-126832">Firestorms and flaming tornadoes: how bushfires create their own ferocious weather systems</a>
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<p>Firestorms are the common term for pyrocumulonimbus bushfires – fires so intense they create their own <a href="http://media.bom.gov.au/social/blog/1618/when-bushfires-make-their-own-weather/">thunderstorms</a>, extreme winds, black hail, and lightning. </p>
<p>While they are very rare, our research published <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL083699">earlier this year</a>, found climate change is making it likely they will become more common in parts of southeast Australia.</p>
<p>We also identified <a href="https://www.nature.com/articles/s41598-019-46362-x.pdf">certain regions</a> in southern and eastern Australia, including near Melbourne’s fringe, that in the second half of this century will be far more vulnerable to these events than others.</p>
<h2>How firestorms happen</h2>
<p>The 2003 Canberra bushfires, devastating on a grand scale, saw a Canberra resident <a href="https://esa.act.gov.au/cbr-be-emergency-ready/bushfires/fire-tornado-video">film a fire tornado</a> for the first time ever. Six years later, the ferocious Black Saturday bushfires in Victoria created <a href="https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/2017JD026577">three separate pyrocumulonimbus events</a>.</p>
<p>More recently, fire storms devastated California in November 2018.</p>
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<p>Pyrocumulonimbus events begin with the intense heat of a very big and fast-burning wildfire, which causes a large and rapidly rising smoke plume. As the plume rises, low atmospheric pressure causes it to expand and cool. Moisture can condense into a type of cloud known as a <em>pyrocumulus</em> - not pyrocumulonimbus, yet. This type of cloud can be common in <a href="https://www.youtube.com/watch?v=44awwgj7kVA">large fires</a>.</p>
<p>However, with the right environmental conditions the plume goes much higher and pyrocumulonimbus clouds can form, towering up to 15km in some cases. As it rises, the plume cools, and the upper part of the clouds form ice particles that collide and can produce lightning.</p>
<p>These thunderstorms can create erratic and dangerously strong wind gusts. These can drive blizzards of embers that ignite spot fires beyond the fire font. </p>
<p>Lightning from the plume can start new fires, well ahead of the main fire. In one case, lightning generated in a pyrocumulonimbus cloud has been recorded starting new fires up to <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017JD026577">100km ahead</a> of the main fire.</p>
<h2>How climate change makes firestorms more likely</h2>
<p>One of the key elements to a firestorm forming is the precondition of the atmosphere above it. We wanted to investigate how a changing climate might affect the likelihood of firestorms happening.</p>
<p><a href="https://www.cawcr.gov.au/technical-reports/CTR_020.pdf">Previous research</a> has found there is more dynamic interaction between a large fire and the atmosphere when the air about 1.5km above the surface is relatively dry, and when there are larger temperature differences across increasing altitudes. </p>
<p>The larger the temperature difference, the more unstable the atmosphere may become. When higher altitudes get cold more quickly than normal, and are also very dry at low levels, it can become more likely that a pyrocumulonimbus event will develop during a large fire.</p>
<p>We used high-resolution climate modelling of projected lower atmospheric instability and dryness conditions to assess the risk of pyrocumulonimbus in southeastern Australia between 2060 and 2079, compared with 1990-2009. We then overlaid this information with the <a href="https://www.csiro.au/en/Research/Environment/Extreme-Events/Bushfire/Fire-danger-meters/Mk5-forest-fire-danger-meter">forest fire danger index</a> to identify particularly dangerous fire days.</p>
<p>We were then able to identify how often dangerous fire weather days occurred at the same time as a dry and unstable atmosphere. Verifying our models against <a href="https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/2017GL076654">past observations</a>, we then examined how often these two characteristics coincided in the future under climate change, should our greenhouse gas emissions remain on their current trajectory.</p>
<p>The results were startling. From 2060 onwards, we saw sharp increases in dangerous fire days across southeast Australia that coincided with atmospheric conditions primed to <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL083699">generate firestorms</a>.</p>
<p>These extremely dangerous days also shifted across seasons, starting to appear in late spring, whereas historically Australian pyrocumulonimbus wildfires have typically been <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL083699">summer phenomena</a>. </p>
<p>Across large areas of Victoria and South Australia, on average, we saw four or five more days every spring that were conducive to pyrocumulonimbus events.</p>
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Read more:
<a href="https://theconversation.com/a-surprising-answer-to-a-hot-question-controlled-burns-often-fail-to-slow-a-bushfire-127022">A surprising answer to a hot question: controlled burns often fail to slow a bushfire</a>
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<p>These were sobering findings, even in a land of extremes like Australia. Our research suggests human-caused climate change has already resulted in <a href="http://nespclimate.com.au/wp-content/uploads/2019/10/A4_4pp_brochure_NESP_ESCC_Bushfires_FINAL_Oct9_2019_WEB.pdf">more dangerous</a> weather conditions for bushfires in recent decades for many regions of Australia. These trends are very likely to increase due to rising greenhouse gas emissions.</p><img src="https://counter.theconversation.com/content/127225/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Dowdy receives funding from the Earth Systems and Climate Change (ESCC) Hub of the National Environmental Science Program (NESP) and various state government research funding programs. </span></em></p><p class="fine-print"><em><span>Jason Evans receives funding from the Australian Research Council, the National Environmental Science Programme Earth Systems and Climate Change Hub, and various NSW state government research funding programs.</span></em></p><p class="fine-print"><em><span>Jason Sharples receives funding from the Australian Research Council and the Bushfire and Natural Hazards CRC. </span></em></p><p class="fine-print"><em><span>Giovanni Di Virgilio and Rick McRae do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Extreme fire risk will overlap with weather patterns to create fire tornadoes more often under climate change.Giovanni Di Virgilio, Research associate, UNSW SydneyAndrew Dowdy, Senior Research Scientist, Australian Bureau of MeteorologyJason Evans, Associate Professor, UNSW SydneyJason Sharples, Associate Professor, School of Physical, Environmental and Mathematical Sciences, UNSW Australia, UNSW SydneyRick McRae, Researcher, Bushfire Cooperative Research Centre, ACT Emergency Services AgencyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/111932012-12-17T19:38:45Z2012-12-17T19:38:45ZTurn and burn: the strange world of fire tornadoes<figure><img src="https://images.theconversation.com/files/18762/original/q343kxf4-1355715541.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Researchers and firefighters have long speculated that fire tornadoes might exist. Now we know they do.</span> <span class="attribution"><span class="source">Dig/AAP</span></span></figcaption></figure><p>We’ve all seen footage of out-of-control bushfires sweeping the Australian landscape, burning out hectares of native forest in their wake. But you might not have heard of a fire tornado, let alone seen one. </p>
<p>For many years now researchers have theorised that fire tornadoes could be possible. Now, in studying the 2003 Canberra bushfires, our colleagues and us have shown fire tornadoes <a href="http://rd.springer.com/article/10.1007/s11069-012-0443-7#page-1">do indeed exist</a>.</p>
<p>So what are fire tornadoes? Where do they come from? And what sort of damage can they cause?</p>
<h2>Fire thunderstorms</h2>
<p>To answer these questions, we first need to understand a separate – but related – phenomenon: fire thunderstorms, also known as <a href="http://en.wikipedia.org/wiki/Pyrocumulonimbus_cloud">pyro-cumulonimbus clouds</a>.</p>
<p>The fires that form these clouds are often burning such large tracts of land that full thunderstorms can form within their plumes.</p>
<p>Lightning from these storms often starts new fires, seen spectacularly in the <a href="http://en.wikipedia.org/wiki/Mount_Lubra_bushfire">January 2006 fire</a> in the Grampians, Victoria.</p>
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<span class="caption">The pyro-cumulonimbus as it approached Canberra in 2003, as seen from a helicopter 20km to the southwest.</span>
<span class="attribution"><span class="source">Stephen Wilkes/NSW Rural Fire Service</span></span>
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<p>Such clouds can also create black hail – a manifestation of the unusual cloud physics and massive quantities of entrained smoke. This phenomenon <a href="http://bit.ly/TKS2WD">was reported</a> in the 2003 Canberra bushfires.</p>
<p>But that’s not all - our research has now shown that pyro-cumulonimbus clouds (pyroCb) can also produce tornadoes.</p>
<h2>In a spin</h2>
<p>Sometimes firefighters report seeing intense <a href="http://en.wikipedia.org/wiki/Fire_whirl">fire whirls</a> – spinning columns of fire – and these are often erroneously called fire tornadoes. But these whirls are directly linked to the ground and to the heat generated by the fire - they are not true fire tornadoes.</p>
<p>A fire tornado is attached to the base of a pyroCb and, like a true tornado, it is a product of instability, moisture and wind shear. The low pressure core of a tornado is famous for picking up objects or water (as in a water spout).</p>
<p>But we’ve now confirmed it can also draw in flames if over a fire front, glowing more than a kilometre into the air.</p>
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<span class="caption">Pine trees in Pierces Creek were snapped off 3m above the ground by tornadic winds in the 2003 Canberra bushfires.</span>
<span class="attribution"><span class="source">Stephen Wilkes/NSW Rural Fire Service</span></span>
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<h2>The 2003 Canberra fire tornado</h2>
<p>Unlike the fire whirls observed by firefighters, the 2003 Canberra fire tornado was linked to the base of a thunderstorm, lifted off the ground, and then touched down again, three times.</p>
<p>What made this fire different to other fires was the wide range of observations being made as the edge of Australia’s capital was threatened.</p>
<p>They included:</p>
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<li>airborne systems that featured a multispectral linescanner, which works like an earth-observation satellite, collecting data in multiple visible and infrared bands</li>
<li>space-based imagery from six satellites</li>
<li>weather radar and photographs</li>
<li>videos from journalists, the public, and air observers, including the remarkable footage taken by Richard Moran for WIN News from the fire brigade commander’s vehicle (see video below).</li>
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<p>We, in collaboration with our colleagues, then used these observations to determine the existence of the fire tornado.</p>
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<h2>Tracing the tornado</h2>
<p>We showed that the weather conditions the fires were burning in were also suitable for tornado formation. We mapped the damage path, from the air and on the ground and could track the tornado in weather radar data.</p>
<p>We placed the contents of photographs in the correct place and time. Ultimately we were able to measure a number of the tornado’s physical properties.</p>
<p>The tornado’s movement over ground was determined from detailed damage mapping and photographic triangulation. Its horizontal and vertical wind speeds were similarly measured and estimated from damage types, using the <a href="http://www.spc.noaa.gov/faq/tornado/ef-scale.html">Enhanced Fujita Tornado Damage scale</a>.</p>
<p>It is now clear that some houses on Canberra’s edge were destroyed by this tornado. Others were damaged by both wind and fire.</p>
<p>So, on top of the already-present risk of bushfires, we now know that residents of Canberra (and elsewhere) face the risk of a tornado bearing down on their home if a fire is particularly fierce. </p>
<p>This indicates that we need to see if the <a href="http://www.abcb.gov.au/about-the-national-construction-code/the-building-code-of-australia">Building Code of Australia</a> might be able to consider tornadic wind loadings in structural designs for bushfire-prone areas.</p>
<p>And, with the bushfire season already upon us, what better time to get such discussions underway.</p><img src="https://counter.theconversation.com/content/11193/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jason Sharples receives funding from the Australian Academy of Science and the Australian Research Council. He works for the University of New South Wales, Canberra. He is affiliated with ACT Rural Fire Service.</span></em></p><p class="fine-print"><em><span>Rick McRae does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>We’ve all seen footage of out-of-control bushfires sweeping the Australian landscape, burning out hectares of native forest in their wake. But you might not have heard of a fire tornado, let alone seen…Rick McRae, Researcher, ACT Emergency Services AgencyJason Sharples, Lecturer, School of Physical, Environmental and Mathematical Sciences, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.