Article | Climate Change: Fire Weather in Australia

By: Francisca Yunis Richter

Published on September 27, 2022

Weather conditions influence the size, intensity, speed and predictability of wildfires, and how dangerous they can be”.

(Bureau of Meteorology, 2017).

According to the Australian Institute for Disaster Resilience (AIDR), the way that fuel ignites, flames form, and fire spreads, are referred to as fire behavior. This is influenced by the interactions between fuels, weather, and geography (AIDR, 2019).

“Vegetation growth can be encouraged by periods of wet weather, increasing the amount of fuel available (grass, leaf litter, twigs, bark). When the weather is hot, the humidity is low and there’s been little recent rain, this vegetation dries out and becomes more flammable. A fire is more likely to start, and continue to burn, in hot, dry and windy weather”. (Bureau of Meteorology, 2019)

Large wildfires can also produce their own weather, known as “pyrocumulonimbus”, which the Australian Bureau of Meteorology describes as a thunderstorm that develops in a fire’s smoke plume. They most frequently develop in big, intense wildfire smoke plumes in Australia, where they can produce dangerous, erratic changes in the behavior of the fire, including variations in fire direction and intensity, making the fire more dangerous and harder to put out (Bureau of Meteorology, 2018). Additionally, the pyrocumulonimbus clouds have the ability to produce violent downbursts and rainfall, both of which can change fire behaviour.

“Pyrocumulonimbus clouds also can produce lighting storms, which can cause new fire spots, for example, on Black Saturday fires, pyrocumulonimbus clouds created a lighting storm in the State of Victoria, starting a new fire 100 km far from the fire front” (Bureau of Meteorology, 2018)

In Australia, the probability of wildfires happening at particular times of the year varies by region, but nowadays, fires can happen at any time of the year, influenced by local factors; in northern Australia, the dry season, which often lasts through winter and spring, is when wildfires are most prevalent. Summer and autumn are the busiest seasons for fires in southern Australia (Bureau of Meteorology, 2017).

Source: fire seasons in different parts of Australia, Bureau of Meteorology (2019)
Source: Pyrocumulonimbus cloud development, Bureau of Meteorology (2018)

Climate Change and Wildfire Risk in Australia

According to the Australian Bureau of Meteorology, through altering temperature, environmental moisture, weather patterns, and fuel conditions, climate change is having an impact on the frequency and severity of wildfire conditions in Australia. Several regions have undergone substantial changes in recent decades that have resulted in more hazardous fire weather conditions; in particular, changes in southern and eastern Australia have resulted in more intense summer conditions as well as an earlier start to the fire season. An important factor affecting fire hazards in Northern Australia, which experiences high fire activity during the dry season, is an increase in monsoonal rainfall that has accelerated fuel growth in recent years (Australian Bureau of Meteorology, 2017).

There is some evidence that climate change may have an impact on the likelihood of dry-lightning fire ignitions. Furthermore, there have been several recent catastrophic fire incidents in Australia linked to intense pyroconvection, such as thunderstorm development in a fire plume, with the current study indicating a long-term trend towards higher risk factors linked to pyroconvection in southeast Australia..

“Fire weather conditions in future years are projected to increase in severity for many regions of Australia, including due to more extreme heat events, with the rate and magnitude of change increasing with greenhouse gas concentrations” (Bureau of Meteorology, n.d).

References

Australian Institute for Disaster Resilience, 2019. Australian Disaster Resilience Glossary. (online) Knowledge.aidr.org.au. Available at: https://knowledge.aidr.org.au/glossary/?wordOfTheDayId=&keywords=fire%20behaviour&alpha=&page=1&results=50&order=AZ (Accessed 6 October 2022).

Bureau of Meteorology (2017). Understanding fire weather. (online) Available at: https://media.bom.gov.au/social/blog/1538/understanding-fire-weather/ (Accessed 27 September 2022).

Bureau of Meteorology. (n. d.). Bushfire weather. Australia’s official weather forecasts & weather radar (online) Available at: http://www.bom.gov.au/weather-services/fire-weather-centre/bushfire-weather/index.shtml (Accessed 27 September 2022).

Bureau of Meteorology (2018) When bushfires make their own weather – Social Media Blog (online) Available at: https://media.bom.gov.au/social/blog/1618/when-bushfires-make-their-own-weather/ (Accessed 27 September 2022).

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