Extreme fire weather is the major driver of severe bushfires in southeast australia

We have constructed a fire weather climatology over North America from 1979 to 2015 using the North American Regional Reanalysis dataset and the Canadian Fire Weather Index (FWI) System. We tested for the presence of trends in potential fire season length, based on a meteorological definition, and extreme fire weather using the non-parametric Theil–Sen slope estimator and Mann–Kendall test. Applying field significance testing (i.e. joint significance of multiple tests) allowed the identification of the locations of significant trends, taking into account spatial correlations. Fire season length was found to be increasing over large areas of North America, especially in eastern Canada and the south-western US, which is consistent with a later fire season end and an earlier fire season start. Both positive and negative trends in potential fire spread days and the 99th percentile of FWI occurred in Canada and the contiguous United States, although the trends of largest magnitude and statistical significance were mostly positive. In contrast, the proportion of trends with significant decreases in these variables were much lower, indicating an overall increase in extreme fire weather. The smaller proportion of significant positive trends found over Canada reflects the truncation of the time series, necessary because assimilation of precipitation observations over Canada ceased in the reanalysis post-2002.

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Increased trends in global extreme fire weather driven predominantly by atmospheric humidity and temperature

10.21203/rs.3.rs-595210/v1 ◽

2021 ◽

Author(s):

Piyush Jain ◽

Dante Castellanos-Acuna ◽

Sean Coogan ◽

John Abatzoglou ◽

Mike Flannigan

Keyword(s):

Global Analysis ◽

Vapour Pressure Deficit ◽

Fire Risk ◽

Dew Point ◽

Fire Weather ◽

Atmospheric Humidity ◽

Weather Index ◽

Fire Weather Index ◽

Temperature Trends ◽

Extreme Fire

Abstract Climate and weather greatly influence wildfire, and recent increases in wildfire activity have been linked to climate change. However, the atmospheric drivers of observed changes have not been articulated globally. We present a global analysis of trends in extreme fire weather from 1979–2020. Significant increases in extreme (95th percentile) annual values of the Fire Weather Index (FWI95), Initial Spread Index (ISI95), and Vapour Pressure Deficit (VPD95) occurred over 26.0%, 26.1%, and 46.1% of the global burnable landmass, respectively. Significant trends corresponded to a 35.8%, 36.0%, and 21.4% increase in mean global FWI95, ISI95, and VPD95, respectively. Relative humidity and temperature were identified as the drivers of significant trends in FWI95 and ISI95 in most regions, largely where temperature trends outpaced dew point trends. We identified relatively few regions in which wind speed or precipitation were drivers. These findings have wide-ranging implications for understanding fire risk in a changing climate.

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Observed increases in extreme fire weather driven by atmospheric humidity and temperature

Nature Climate Change ◽

10.1038/s41558-021-01224-1 ◽

2021 ◽

Author(s):

Piyush Jain ◽

Dante Castellanos-Acuna ◽

Sean C. P. Coogan ◽

John T. Abatzoglou ◽

Mike D. Flannigan

Keyword(s):

Fire Weather ◽

Atmospheric Humidity ◽

Extreme Fire

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Evolution of a pyrocumulonimbus event associated with an extreme wildfire in Tasmania, Australia

Natural Hazards and Earth System Science ◽

10.5194/nhess-20-1497-2020 ◽

2020 ◽

Vol 20 (5) ◽

pp. 1497-1511 ◽

Cited By ~ 2

Author(s):

Mercy N. Ndalila ◽

Grant J. Williamson ◽

Paul Fox-Hughes ◽

Jason Sharples ◽

David M. J. S. Bowman

Keyword(s):

Weather Forecasting ◽

Fire Severity ◽

Atmospheric Stability ◽

Lower Atmosphere ◽

Fire Weather ◽

Natural Ecosystems ◽

Near Surface ◽

South Eastern ◽

Crown Defoliation ◽

Extreme Fire

Abstract. Extreme fires have substantial adverse effects on society and natural ecosystems. Such events can be associated with the intense coupling of fire behaviour with the atmosphere, resulting in extreme fire characteristics such as pyrocumulonimbus cloud (pyroCb) development. Concern that anthropogenic climate change is increasing the occurrence of pyroCbs globally is driving more focused research into these meteorological phenomena. Using 6 min scans from a nearby weather radar, we describe the development of a pyroCb during the afternoon of 4 January 2013 above the Forcett–Dunalley fire in south-eastern Tasmania. We relate storm development to (1) near-surface weather using the McArthur forest fire danger index (FFDI) and the C-Haines index, the latter of which is a measure of the vertical atmospheric stability and dryness, both derived from gridded weather reanalysis for Tasmania (BARRA-TA); and (2) a chronosequence of fire severity derived from remote sensing. We show that the pyroCb rapidly developed over a 24 min period on the afternoon of 4 January, with the cloud top reaching a height of 15 km. The pyroCb was associated with a highly unstable lower atmosphere (C-Haines value of 10–11) and severe–marginally extreme (FFDI 60–75) near-surface fire weather, and it formed over an area of forest that was severely burned (total crown defoliation). We use spatial patterns of elevated fire weather in Tasmania and fire weather during major runs of large wildfires in Tasmania for the period from 2007 to 2016 to geographically and historically contextualise this pyroCb event. Although the Forcett–Dunalley fire is the only known record of a pyroCb in Tasmania, our results show that eastern and south-eastern Tasmania are prone to the conjunction of high FFDI and C-Haines values that have been associated with pyroCb development. Our findings have implications for fire weather forecasting and wildfire management, and they highlight the vulnerability of south-east Tasmania to extreme fire events.

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