@article {bnh-7342, title = {Climate Change Significantly Alters Future Wildfire Mitigation Opportunities in Southeastern Australia}, journal = {Geophysical Research Letters}, volume = {47}, year = {2020}, month = {07/2020}, abstract = {

Prescribed burning is used globally to mitigate the risks of wildfires, with severe wildfires increasing in frequency in recent decades. Despite their importance in wildfire management, the nature of future changes to prescribed burn windows under global warming remains uncertain. We use a regional climate projection ensemble to provide a robust spatiotemporal quantification of statistically significant future changes in prescribed burn windows for southeastern Australia. There are significant decreases during months presently used for prescribed burning, that is, in March to May in 2060{\textendash}2079 versus 1990{\textendash}2009 across several temperate regions. Conversely, burn windows show widespread significant increases in June to August, that is, months when burns have rarely occurred historically, and also in spring (September{\textendash}October). Overall, projected changes in temperature and fuel moisture show the most widespread and largest decreases (or increases) in the number of days within their respective ranges suitable for conducting burns. These results support wildfire risk mitigation planning.

}, keywords = {climate modeling, environmental change, Fire weather, Natural hazards, prescribed burns, risk mitigation}, doi = {https://doi.org/10.1029/2020GL088893}, url = {https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2020GL088893}, author = {Giovanni Di Virgillio and Jason P. Evans and Hamish Clarke and Jason J. Sharples and Annette Hirsch and Melissa Anne Hart} } @article {bnh-7478, title = {Climate Change Increases the Potential for Extreme Wildfires}, journal = {Geophysical Research Letters}, volume = {46}, year = {2019}, month = {07/2019}, pages = {8517-8526}, abstract = {


Pyrocumulonimbus (pyroCb) wildfires cause devastation in many regions globally. Given that fire-atmosphere coupling is associated with pyroCbs, future changes in coincident high index values of atmospheric instability and dryness (C-Haines) and near-surface fire weather are assessed for southeastern Australia using a regional climate projection ensemble. We show that observed pyroCb events occur predominantly on forested, rugged landscapes during extreme C-Haines conditions, but over a wide range of surface fire weather conditions. Statistically significant increases in the number of days where both C-Haines and near-surface fire weather values are conducive to pyroCb development are projected across southeastern Australia, predominantly for November (spring), and less strongly for December (summer) in 2060-2079 versus 1990-2009, with future C-Haines increases linked to increased 850-hPa dewpoint depression. The increased future occurrence of conditions conducive to pyroCb development and their extension into spring have implications for mitigating these dangerous wildfires and urbanizing fire-prone landscapes.

}, keywords = {atmospheric instability, dewpoint depression, Fire weather, Natural hazards, pyrocumulonimbus, regional climate modeling}, doi = {https://doi.org/10.1029/2019GL083699}, url = {https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL083699}, author = {Giovanni Virgilio and Jason P. Evans and Stephanie Blake and Matthew Armstrong and Dowdy, Andrew J and Jason J. Sharples and McRae} } @article {bnh-5102, title = {Estimating fire severity and carbon emissions over Australian tropical savannahs based on passive microwave satellite observations}, journal = {International Journal of Remote Sensing}, year = {2018}, month = {04/2018}, abstract = {

We investigated the use of a recently developed satellite-based vegetation optical depth (VOD) data set to estimate fire severity and carbon emission over Australian tropical savannahs. VOD is sensitive to the dynamics of all aboveground vegetation and available nearly every two days. For areas burned during 2003{\textendash}2010, we calculated the VOD change (ΔVOD) pre- and post-fire and the associated loss in the above ground biomass carbon. ΔVOD agreed well with the Normalized Burn Ratio change (ΔNBR) which is the metric used to estimate fire severity and carbon loss compared well with modelled emissions from the Global Fire Emissions Database (GFED). We found that the ΔVOD and ΔNBR are generally linearly related. The Pearson correlation coefficients (r) between VOD- and GFED-based fire carbon emissions for monthly and annual total estimates are very high, 0.92 and 0.96, respectively. A key feature of fire carbon emissions is the strong inter-annual variation, ranging from 21.1 Mt in 2010 to 84.3 Mt in 2004. This study demonstrates that a reasonable estimate of fire severity and carbon emissions can be achieved in a timely manner based on multiple satellite observations over Australian tropical savannahs, which can be complementary to the currently used approaches.

}, doi = {https://doi.org/10.1080/01431161.2018.1460507}, url = {https://www.tandfonline.com/doi/abs/10.1080/01431161.2018.1460507}, author = {Xi Chen and Y.Y Liu and Jason P. Evans and R.M. Parinussa and Albert van Dijk and Marta Yebra} } @article {bnh-5262, title = {Estimating grassland curing with remotely sensed data}, journal = {Natural Hazards and Earth System Sciences }, year = {2018}, month = {06/2018}, chapter = {1535}, abstract = {

Wildfire can become a catastrophic natural hazard, especially during dry summer seasons in Australia. Severity is influenced by various meteorological, geographical, and fuel characteristics. Modified Mark 4 McArthur{\textquoteright}s Grassland Fire Danger Index (GFDI) is a commonly used approach to determine the fire danger level in grassland ecosystems. The degree of curing (DOC, i.e. proportion of dead material) of the grass is one key ingredient in determining the fire danger. It is difficult to collect accurate DOC information in the field, and therefore ground-observed measurements are rather limited. In this study, we explore the possibility of whether adding satellite-observed data responding to vegetation water content (vegetation optical depth, VOD) will improve DOC prediction when compared with the existing satellite-observed data responding to DOC prediction models based on vegetation greenness (normalised difference vegetation index, NDVI). First, statistically significant relationships are established between selected ground-observed DOC and satellite-observed vegetation datasets (NDVI and VOD) with an r2 up to 0.67. DOC levels estimated using satellite observations were then evaluated using field measurements with an r2 of 0.44 to 0.55. Results suggest that VOD-based DOC estimation can reasonably reproduce ground-based observations in space and time and is comparable to the existing NDVI-based DOC estimation models.

}, doi = {10.5194/nhess-18-1535-2018}, url = {https://www.nat-hazards-earth-syst-sci.net/18/1535/2018/nhess-18-1535-2018.pdf}, author = {Jason J. Sharples and Wasin Chaivaranont and Jason P. Evans and Yi Y.Liu} } @conference {bnh-3874, title = {Extreme weather: improved data products on bushfires, thunderstorms, tropical cyclones and east coast lows}, booktitle = {AFAC17}, year = {2017}, month = {09/2017}, publisher = {Bushfire and Natural Hazards CRC}, organization = {Bushfire and Natural Hazards CRC}, address = {Sydney}, abstract = {

Extreme weather events can cause a wide range of impacts on different regions throughout Australia, including costs associated with damage to natural and built environments. Effective disaster risk reduction, emergency response, infrastructure design/operation, planning and policy making all require data and information about how extreme events will change in the future.

New data products and information are currently being developed on bushfires, tropical cyclones, east coast lows and thunderstorms (including associated hazards such as extreme rainfall, winds, hail and lightning) by a project on extreme weather events in the National Environmental Science Programme \ (NESP: \ http://nespclimate.com.au/extreme-weather-projections/). \ This \ project addresses knowledge gaps on the past and future frequency and intensity of these phenomena, including the physical processes that influence the long-term variations in their characteristics, to \ produce \ practical \ tools \ and \ guidance \ products \ for \ use \ by \ planners \ and \ decision \ makers throughout Australia.

}, author = {Dowdy, Andrew J and Harvey Ye and KJ Tory and Evans, Alex and Lavender, Sally and Thatcher, Marcus and Rafter, Tony and Osbrough, Stacey and Kevin Walsh and Cavicchia, Leone and Jason P. Evans and Catto, Jennifer} } @article {bnh-3925, title = {Modelling the dynamic behaviour of junction fires with a coupled fire-atmosphere model}, journal = {International Journal of Wildland Fire}, volume = {26}, year = {2017}, month = {04/2017}, pages = {331-344}, chapter = {331}, abstract = {

Dynamic fire behaviour involves rapid changes in fire behaviour without significant changes in ambient conditions, and can compromise firefighter and community safety. Dynamic fire behaviour cannot be captured using spatial implementations of empirical fire-spread models predicated on the assumption of an equilibrium, or quasi-steady, rate of spread. In this study, a coupled atmosphere{\textendash}fire model is used to model the dynamic propagation of junction fires, i.e. when two firelines merge at an oblique angle. This involves very rapid initial rates of spread, even with no ambient wind. The simulations are in good qualitative agreement with a previous experimental study, and indicate that pyro-convective interaction between the fire and the atmosphere is the key mechanism driving the dynamic fire propagation. An examination of the vertical vorticity in the simulations, and its relationship to the fireline geometry, gives insight into this mechanism. Junction fires have been modelled previously using curvature-dependent rates of spread. In this study, however, although fireline geometry clearly influences rate of spread, no relationship is found between local fireline curvature and the simulated instantaneous local rate of spread. It is possible that such a relationship may be found at larger scales.

}, doi = {10.1071/WF16079}, url = {http://www.publish.csiro.au/wf/WF16079}, author = {Thomas, C. M. and Jason J. Sharples and Jason P. Evans} } @article {bnh-3284, title = {Natural hazards in Australia: droughts}, journal = {Climatic Change}, volume = {139}, year = {2016}, month = {11/2016}, pages = {37-54}, chapter = {37}, abstract = {

Droughts are a recurrent and natural part of the Australian hydroclimate, with evidence of drought dating back thousands of years. However, our ability to monitor, attribute, forecast and manage drought is exposed as insufficient whenever a drought occurs. This paper summarises what is known about drought hazard, as opposed to the impacts of drought, in Australia and finds that, unlike other hydroclimatic hazards, we currently have very limited ability to tell when a drought will begin or end. Understanding, defining, monitoring, forecasting and managing drought is also complex due to the variety of temporal and spatial scales at which drought occurs and the diverse direct and indirect causes and consequences of drought. We argue that to improve understanding and management of drought, three key research challenges should be targeted: (1) defining and monitoring drought characteristics (i.e. frequency, start, duration, magnitude, and spatial extent) to remove confusion between drought causes, impacts and risks and better distinguish between drought, aridity, and water scarcity due to over-extractions; (2) documenting historical (instrumental and pre-instrumental) variation in drought to better understand baseline drought characteristics, enable more rigorous identification and attribution of drought events or trends, inform/evaluate hydrological and climate modelling activities and give insights into possible future drought scenarios; (3) improving the prediction and projection of drought characteristics with seasonal to multidecadal lead times and including more realistic modelling of the multiple factors that cause (or contribute to) drought so that the impacts of natural variability and anthropogenic climate change are accounted for and the reliability of long-term drought projections increases.

}, doi = {10.1007/s10584-016-1798-7}, url = {http://link.springer.com/article/10.1007/s10584-016-1798-7}, author = {Anthony S. Kiem and Fiona Johnson and Seth Westra and Albert van Dijk and Jason P. Evans and O{\textquoteright}Donnell, Alison J. and Alexandra Rouillard and Cameron Barr and Johnathon Tyler and Mark Thyer and Doerte Jakob and Fitsum Woldemeskel and Bellie Sivakumar and Raj Mehrotra} } @article {bnh-3282, title = {Natural hazards in Australia: extreme bushfire}, journal = {Climatic Change}, volume = {139}, year = {2016}, month = {11/2016}, pages = {85-99}, chapter = {85}, abstract = {

Bushfires are one of the most frequent natural hazards experienced in Australia. Fires play an important role in shaping the landscape and its ecological dynamics, but may also have devastating effects that cause human injuries and fatalities, as well as broad-scale environmental damage. While there has been considerable effort to quantify changes in the occurrence of bushfire in Australia, a comprehensive assessment of the most extreme bushfire cases, which exact the greatest economic and environmental impacts, is lacking. In this paper we reflect upon recently developed understanding of bushfire dynamics to consider (i) historical changes in the occurrence of extreme bushfires, and (ii) the potential for increasing frequency in the future under climate change projections. The science of extreme bushfires is still a developing area, thus our conclusions about emerging patterns in their occurrence should be considered tentative. Nonetheless, historical information on noteworthy bushfire events suggests an increased occurrence in recent decades. Based on our best current understanding of how extreme bushfires develop, there is strong potential for them to increase in frequency in the future. As such there is a pressing need for a greater understanding of these powerful and often destructive phenomena.

}, doi = {10.1007/s10584-016-1811-1}, url = {http://link.springer.com/article/10.1007/s10584-016-1811-1}, author = {Jason J. Sharples and Geoffrey J. Cary and Paul Fox-Hughes and Mooney, Scott and Jason P. Evans and Fletcher, Michael-Shawn and Michael Fromm and Grierson, Pauline and Rick McRae and Baker, Patrick} } @article {bnh-3283, title = {Natural hazards in Australia: floods}, journal = {Climatic Change}, volume = {139}, year = {2016}, month = {11/2016}, pages = {21-35}, chapter = {21}, abstract = {

Floods are caused by a number of interacting factors, making it remarkably difficult to explain changes in flood hazard. This paper reviews the current understanding of historical trends and variability in flood hazard across Australia. Links between flood and rainfall trends cannot be made due to the influence of climate processes over a number of spatial and temporal scales as well as landscape changes that affect the catchment response. There are also still considerable uncertainties in future rainfall projections, particularly for sub-daily extreme rainfall events. This is in addition to the inherent uncertainty in hydrological modelling such as antecedent conditions and feedback mechanisms.

Research questions are posed based on the current state of knowledge. These include a need for high-resolution climate modelling studies and efforts in compiling and analysing databases of sub-daily rainfall and flood records. Finally there is a need to develop modelling frameworks that can deal with the interaction between climate processes at different spatio-temporal scales, so that historical flood trends can be better explained and future flood behaviour understood.

}, doi = {10.1007/s10584-016-1689-y}, url = {http://link.springer.com/article/10.1007/s10584-016-1689-y}, author = {Fiona Johnson and Christopher J. White and Albert van Dijk and Marie Ekstrom and Jason P. Evans and Doerte Jakob and Anthony S. Kiem and M. Leonard and Alexandra Rouillard and Seth Westra} } @conference {bnh-1638, title = {Threshold Behaviour in Dynamic Fire Propagation Conference Paper 2014}, booktitle = {Bushfire and Natural Hazards CRC and AFAC Wellington Conference 2014}, year = {2015}, month = {02/2015}, abstract = {

Recent research has demonstrated that under conditions of extreme fire weather, bushfires burning in rugged terrain can exhibit distinctly dynamic patterns of propagation, which can have a dramatic effect on subsequent fire development. Coupled fire-atmosphere modelling using large eddy simulation has been useful in shedding light on the physical mechanisms underlying these phenomena, for example highlighting the important role of fire-induced vorticity. In particular it has confirmed that the onset of dynamic modes of fire propagation is subject to a number of environmental thresholds. This is not the first time that the existence of threshold behaviour in combustion-related systems has been identified. In this paper we provide a brief summary of some combustion-related systems that exhibit threshold behaviour. Specifically we discuss the emergence of dynamic modes of fire propagation in exceedingly simple representations of combustion systems, and the existence of environmental thresholds relating to the propagation of wildfires in rugged terrain. Most significantly, we present new research that specifically investigates the environmental precursors necessary to drive a particular type of dynamic fire propagation known as vorticity-driven lateral spread (VLS). This research extends previous coupled fire-atmosphere modelling, to specifically consider the effect of wind speed and topographic slope ingenerating the fire-induced vorticity necessary to drive VLS.
The modelling results indicate the existence of environmental thresholds beyond which VLS is likely to occur. The results also indicate that the transition from quasi-steady to dynamic fire propagation can be quite abrupt, requiring only minimal changes in wind speed and slope for onset. The propensity for dynamic interactions to produce erratic and dangerous fire behaviour has strong implications for firefighter and community safety.

}, author = {Jason J. Sharples and Colin Simpson and Jason P. Evans and Rick McRae} }