@article {bnh-8379, title = {Fire coalescence and mass spot fire dynamics - final project report}, number = {736}, year = {2023}, month = {04/2023}, institution = {Natural Hazards Research Australia}, abstract = {

The Fire coalescence and mass spot fire dynamics project (the Spotfire Project) was one of the core research projects within the Bushfire and Natural Hazards CRC{\textquoteright}s Bushfire Predictive Services research cluster. Specifically, the Spotfire Project was focused on enhancing our understanding of the physical processes involved in spot fire development and coalescence and developing computationally efficient mathematical models that can accurately account for these the patterns of bushfire propagation associated with mass spotting and other modes of dynamic fire behaviour. Current operational models and associated simulation platforms are predicated on the assumptions that fires spread in a quasi-steady manner and that different parts of a fire line evolve independently of other parts {\textendash} both of these assumptions are manifestly untrue during mass spotting events.

The research took a multifaceted approach, which drew upon experimentation, computer simulation and mathematical modelling to develop a new dynamic modelling framework that permits faster-than-real-time simulation of fire propagation incorporating dynamic drivers. Experimentation took place at both laboratory and field scales. Laboratory experimentation was conducted in the CSIRO Pyrotron and in collaboration with Portuguese colleagues at the Centre for the Study of Forest Fires. Field scale experiments were also conducted in Portugal. The experiments provided insights into the dynamic nature of fire behaviour and provided data for calibration and validation of the models under development.

Coupled fire-atmosphere models were used to perform idealized simulations of various scenarios involving dynamic fire propagation. The model output provided detailed quantitative insights into the physical processes driving dynamic fire propagation and were used to inform development of new mathematical models. The mathematical model developed during the project is essentially a two-dimensional version of a coupled fire-atmosphere model {\textendash} it incorporates the feedback between the fire and the atmosphere but within the two-dimensional Spark fire simulation platform.

The research has yielded many important and significant insights into the behaviour of coalescing spot fires, and these insights have enhanced our understanding of the processes driving fire propagation and the way we model dynamic fire behaviours. These have in turn provided new understanding of violent pyroconvective events and extreme bushfire development.

The most significant research outcome was the development of the pyrogenic potential model, which permits world{\textquoteright}s first capability to model dynamic modes of fire propagation (e.g., vorticity-driven lateral spread) using a two-dimensional simulation framework. This means that explicitly modelling such effects in operational timeframes is now a feasible option. The research has also examined various other issues related to the spotting process and dynamic fire propagation more generally. These include: the effects of wind-terrain interaction on ember trajectories and the likely distribution of spot fires downwind of complex terrain, the influence of spot fires on the overall rate of spread of a fire, the influence of terminal velocity assumptions on ember trajectory modelling, the influence of fuel characteristics (e.g., bulk density) on spot fire development and pyroconvective feedback, the role of fine scale vorticity effects on dynamic fire behaviour, and development of simple measures of pyroconvective potential.

There is considerable utilisation potential for the research findings. The advances in fire behaviour modelling are easily incorporated within the Spark simulator platform. Given that Spark has been formally chosen by AFAC to be the new national bushfire prediction platform, the project{\textquoteright}s research findings will eventually be available to all involved in operational prediction of bushfire propagation. Moreover, the insights into dynamic fire behaviours provided by the project will form the basis for new firefighter training and education materials that will equip operational personnel with better knowledge of the full spectrum of possible fire behaviours in given scenarios. This will improve situational awareness, with benefits for firefighter safety.

The project has also developed a new mapping product that identifies regions prone to mass spotting in association with vorticity-driven lateral spread. This will be available to fire management agencies and other relevant organisations, to assist with fire behaviour prediction, with special relevance to anticipating blow-up fire events and extreme bushfire development.

Overall, the Spotfire Project has presented a new paradigm for understanding fire behaviour and has made the first significant advances towards the next generation of operational models. The insights gained from the research complements and extends existing fire behaviour knowledge in a way that enhances our ability to deal with the increasing bushfire threat into the future.

}, issn = {736}, author = {Jason J. Sharples and James Hilton and Sullivan, Andrew and Badlan, R} } @article {bnh-8343, title = {Spotfire utilisation project: implementation of the VLS filter}, number = {730}, year = {2022}, month = {05/2022}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

The aim of this research was to produce an operational tool to assist fire agency personnel in assessing the potential for extreme bushfire development. Specifically, this work{\textquoteright}s intention was to aid in the identification of regions of the landscape that are prone to mass spotting and other dynamic fire behaviour associated with vorticity-driven lateral spread (VLS). The research was divided into three phases: 1) calibration of the slope scale to each DEM, 2) creation of the filter (first and second order) and finally refinement of the filter and, 3) develop training material and ensure filters and related documents are distributed to relevant personnel.

The first-order and second-order wind-terrain filter enables the user to identify parts of the terrain which are susceptible to VLS through its established association with steep or broken leeward facing terrain elements. This is achieved using terrain attributes such as topographic slope, aspect, and profile curvature, as well as environmental variables such as the wind speed and direction. This builds upon the research initially undertaken as part of the original Bushfire Cooperative Research Centre.

This report summarises the three phases of the project, during which time the researchers have gained familiarity and VLS mapping capability with the GIS software {\textquotedblleft}ArcGIS Pro{\textquotedblright}, which is used to create and validate the wind-terrain filters. This facilitated the two main research objectives {\textendash} to develop and then refine the first order and second order wind-terrain filters so that they may be applied using DEMs of any resolution.

Initially, this involved manual tuning of the first-order wind-terrain filter{\textquoteright}s parameters to fit a number of calibration events. This tuning was also confirmed through analyses of slope distributions over various landscape domains. These static cases were then validated with real case conditions and the filter compared to areas where VLS was known to have occurred. Scaling thresholds for the 30, 90 and 250 metre resolution DEMs were also evaluated explicitly, and a general linear model has been determined to allow estimation of parameter thresholds for more general DEM resolutions.

The second-order filter was then designed and tested in a similar manner to the first-order filter.\  The two filters were then merged into a combined operational product, which was also validated using known cases of VLS. \ Both filters are presented here - separately and as a combined product - for the operational consideration of end-users. \ End-user feedback was then evaluated to further tailor the operational product to specific operational needs, platforms, and formats. Due to travel restrictions static filters have been produced for immediate use. Development of a dynamic mapping tool is also continuing in which other factors such as the forecast wind speed and direction (and potentially other variables) can be incorporated automatically to provide heightened operational intelligence on extreme bushfire development.

}, issn = {730}, author = {Badlan, R and Jason J. Sharples} } @article {bnh-8115, title = {Derivation of a Bayesian fire spread model using large-scale wildfire observations}, journal = {Environmental Modelling \& Software}, year = {2021}, month = {07/2021}, abstract = {

Models that predict wildfire rate of spread (ROS) play an important role in decision-making during firefighting operations, including fire crew placement and timing of community evacuations. Here, we use a large set of remotely sensed wildfire observations, and explanatory data (focusing on weather), to demonstrate a Bayesian probabilistic ROS modelling approach. Our approach has two major advantages: (1) Using actual wildfire observations, instead of controlled fire observations, makes models developed well-suited to wildfire prediction; (2) Bayesian modelling accounts for the complex nature of wildfire spread by explicitly considering uncertainty in the data to produce probabilistic ROS predictions. We show that highly informative probabilistic predictions can be made from a simple Bayesian model containing wind speed, relative humidity and soil moisture. We also compare Bayesian model predictions to those of widely used deterministic ROS models in Australia.

}, keywords = {Wildfire Bushfire Fire behaviour Bayesian Bayesian modelling Rate of Spread}, doi = {https://doi.org/10.1016/j.envsoft.2021.105127}, url = {https://www.sciencedirect.com/science/article/abs/pii/S1364815221001705}, author = {Michael Storey and Bedward, M. and Owen Price and Ross Bradstock and Jason J. Sharples} } @article {bnh-7795, title = {Experiments on the influence of spot fire and topography interaction on fire rate of spread}, journal = {PLOS ONE}, volume = {16}, year = {2021}, month = {01/2021}, abstract = {

Spotting is thought to increase wildfire rate of spread (ROS) and in some cases become the main mechanism for spread. The role of spotting in wildfire spread is controlled by many factors including fire intensity, number of and distance between spot fires, weather, fuel characteristics and topography. Through a set of 30 laboratory fire experiments on a 3 m x 4 m fuel bed, subject to air flow, we explored the influence of manually ignited spot fires (0, 1 or 2), the presence or absence of a model hill and their interaction on combined fire ROS (i.e. ROS incorporating main fire and merged spot fires). During experiments conducted on a flat fuel bed, spot fires (whether 1 or 2) had only a small influence on combined ROS. Slowest combined ROS was recorded when a hill was present and no spot fires were ignited, because the fires crept very slowly downslope and downwind of the hill. This was up to, depending on measurement interval, 5 times slower than ROS in the flat fuel bed experiments. However, ignition of 1 or 2 spot fires (with hill present) greatly increased combined ROS to similar levels as those recorded in the flat fuel bed experiments (depending on spread interval). The effect was strongest on the head fire, where spot fires merged directly with the main fire, but significant increases in off-centre ROS were also detected. Our findings suggest that under certain topographic conditions, spot fires can allow a fire to overcome the low spread potential of downslopes. Current models may underestimate wildfire ROS and fire arrival time in hilly terrain if the influence of spot fires on ROS is not incorporated into predictions.

}, keywords = {air flow, analysis of variance, Bushfire, combustion, fire research, fire suppression technology, fuels, rotors}, doi = {https://doi.org/10.1371/journal.pone.0245132}, url = {https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0245132}, author = {Michael Storey and Owen Price and M. Almeida and Carlos Ribeiro and Ross Bradstock and Jason J. Sharples} } @article {bnh-8288, title = {Interactive influence of ENSO and IOD on contiguous heatwaves in Australia}, journal = {Environmental Research Letters}, year = {2021}, month = {11/2021}, abstract = {

Australian heatwaves have a significant impact on society. Most previous studies focus on understanding them in terms of frequency, duration, intensity, and timing. However, understanding the spatial characteristics of heatwaves, particularly those occurring in contiguous regions at the same time (here referred to as contiguous heatwaves), is still largely unexplored. Here, we analyse changes in spatial characteristics of contiguous heatwaves in Australia during 1958-2020 using observational data. Our results show that extremely large contiguous heatwaves are covering significantly larger areas and getting significantly longer during the recent period (1989/90-2019/20) compared to the historical period (1958/59-1988/89). We also investigated the association of contiguous heatwaves in Australia with interactions of the El Ni{\~n}o{\textendash}Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) using a large multi-member ensemble of a physical climate model. We found that areal magnitude, total area, median duration, and maximum area of large and extremely large contiguous heatwaves in Australia are significantly higher (lower) during the strong El Ni{\~n}o (Es), strong El Ni{\~n}o co-occurring with strong IOD positive (Es-IPs), and with moderate IOD positive (Es-IPm) (co-occurring strong La Ni{\~n}a with the strong IOD negative (Ls-INs)) seasons relative to the neutral seasons (where both ENSO and IOD are in neutral phase). During the Es, Es-IPm, and Es-IPs seasons, the large-scale physical mechanisms are characterised by anticyclonic highs over the southeast and cyclonic lows over the northwest of Australia, favouring the occurrence and intensification of heatwaves in Australia. These results provide insights into the driving mechanisms of contiguous heatwaves in Australia.

}, keywords = {Climate and Earth system modelling, ENSO, heatwaves, IOD}, doi = {https://doi.org/10.1088/1748-9326/ac3e9a}, url = {https://iopscience.iop.org/article/10.1088/1748-9326/ac3e9a}, author = {P Jyoteeshkumar reddy and Sarah Perkins-Kirkpatrick and Jason J. Sharples} } @article {bnh-7834, title = {Modulating influence of drought on the synergy between heatwaves and dead fine fuel moisture content of bushfire fuels in the Southeast Australian region}, journal = {Weather and Climate Extremes}, volume = {31}, year = {2021}, month = {03/2021}, abstract = {

During the 2019-20 summer season, Australia experienced frequent heatwave events with scorching temperatures and massive bushfires with dense smoke. These catastrophic heatwaves and bushfires resulted in huge socio-economic and ecological losses. The frequency and intensity of both heatwaves and bushfires are projected to increase in the future warming world. While considerable effort has been directed at understanding the physical mechanisms of these individual extreme events, an investigation of their interaction is lacking. We focus on the relationship between heatwaves and bushfire fuels by considering dead fine fuel moisture content, a critical factor that regulates the intensity, spread rate and the likelihood of profuse spotting of fires. We investigate the relationship by exploring the statistical correlations between various heatwave characteristics (frequency, duration, magnitude, and amplitude) and mean dead fine fuel moisture content over southeast Australia in the peak heat and fire season. This relationship varies among different heatwave characteristics as well as with regions. The prolonged duration of a heatwave is well associated with dead fine fuel dryness around the southeastern parts of the Southeast Australian region, whereas the hotter heatwave season favours the lower dead fine fuel moisture content over the Northeast parts of the Southeast Australia and central Victorian region. Results also suggest that dead fine fuel moisture content is significantly decreased on heatwave days compared to non-heatwave days. Lastly, we explored the effects of rainfall deficit on the relationship between heatwave and mean dead fine fuel moisture content by splitting the seasons based on the Standard Precipitation Index (SPI). Results show that the correlation strength is both seasonally and regionally dependent.

}, keywords = {Australia, bushfires, Drought, Extreme events, fuel moisture content, heatwaves}, doi = {https://doi.org/10.1016/j.wace.2020.100300}, url = {https://www.sciencedirect.com/science/article/pii/S2212094720303133}, author = {P Jyoteeshkumar reddy and Jason J. Sharples and Sophie Lewis and Sarah Perkins-Kirkpatrick} } @article {bnh-7838, title = {A response to comments of Cruz et al. on: {\textquoteleft}Simulation study of grass fire using a physics-based model: striving towards numerical rigour and the effect of grass height on the rate of spread{\textquoteright}}, journal = {International Journal of Wildland Fire}, year = {2021}, month = {02/2021}, abstract = {

In response to Cruzet al.(2020b) (hereafter: CSG20), we would like to clarify that we are committed to further research into the mechanisms that drive fire spread in grassland fuels, and are open to making the most of synergies that exist between various programs of research. As demonstrated by Filippiet al.(2013), Kochanskiet al.(2013), Clementset al.(2019), etc., there is much to be gained by combining detailed experimental data with rigorous computational modelling.

}, keywords = {Byram number, fuel height, grass fire, modes of fire propagation, rate of spread.}, doi = {https://doi.org/10.1071/WF20091}, url = {https://www.publish.csiro.au/WF/WF20091}, author = {Duncan Sutherland and Jason J. Sharples and William Mell and Khalid Moinuddin} } @article {bnh-6874, title = {Analysis of Variation in Distance, Number, and Distribution of Spotting in Southeast Australian Wildfires}, journal = {Fire}, volume = {3}, year = {2020}, month = {04/2020}, abstract = {

Spotting during wildfires can significantly influence the way wildfires spread and reduce the chances of successful containment by fire crews. However, there is little published empirical evidence of the phenomenon. In this study, we have analysed spotting patterns observed from 251 wildfires from a database of over 8000 aerial line scan images capturing active wildfire across mainland southeast Australia between 2002 and 2018. The images were used to measure spot fire numbers, number of {\textquotedblleft}long-distance{\textquotedblright} spot fires (\> 500 m), and maximum spotting distance. We describe three types of spotting distance distributions, compare patterns among different regions of southeast Australia, and associate these with broad measures of rainfall, elevation, and fuel type. We found a relatively high correlation between spotting distance and numbers; however, there were also several cases of wildfires with low spot fire numbers producing very long-distance spot fires. Most long-distance spotting was associated with a {\textquotedblleft}multi-modal{\textquotedblright} distribution type, where high numbers of spot fires ignite close to the source fire and isolated or small clumps of spot fires ignite at longer distances. The multi-modal distribution suggests that current models of spotting distance, which typically follow an exponential-shaped distribution, could underestimate long-distance spotting. We also found considerable regional variation in spotting phenomena that may be associated with significant variation in rainfall, topographic ruggedness, and fuel descriptors. East Victoria was the most spot-fire-prone of the regions, particularly in terms of long-distance spotting.

}, keywords = {spot fire; spotting distance; spotting distribution; wildfire behaviour}, doi = {https://doi.org/10.3390/fire3020010}, url = {https://www.mdpi.com/2571-6255/3/2/10}, author = {Michael Storey and Owen Price and Ross Bradstock and Jason J. Sharples} } @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-6737, title = {Deconstructing factors contributing to the 2018 fire weather in Queensland, Australia}, volume = {101}, year = {2020}, month = {02/2020}, pages = {S15-S21}, edition = {1}, abstract = {

Factors including the circulation pattern and antecedent conditions contributed to 2018 northeast Australian fires. High background temperatures also played a role for which model evidence suggests an anthropogenic influence.

}, keywords = {Fire, Fire weather, Queensland}, doi = {10.1175/BAMS-D-19-0144.1}, url = {https://www.ametsoc.org/ams/index.cfm/publications/bulletin-of-the-american-meteorological-society-bams/explaining-extreme-events-from-a-climate-perspective/}, author = {Sophie Lewis and Stephanie Blake and Blair Trewin and Mitchell Black and Dowdy, Andrew J and Sarah Perkins-Kirkpatrick and Andrew King and Jason J. Sharples} } @article {bnh-6754, title = {Drivers of long-distance spotting during wildfires in south-eastern Australia}, journal = {International Journal of Wildland Fire}, year = {2020}, month = {03/2020}, abstract = {

We analysed the influence of wildfire area, topography, fuel, surface weather and upper-level weather conditions on long-distance spotting during wildfires. The analysis was based on a large dataset of 338 observations, from aircraft-acquired optical line scans, of spotting wildfires in south-east Australia between 2002 and 2018. Source fire area (a measure of fire activity) was the most important predictor of maximum spotting distance and the number of long-distance spot fires produced (i.e. \>500 m from a source fire). Weather (surface and upper-level), vegetation and topographic variables had important secondary effects. Spotting distance and number of long-distance spot fires increased strongly with increasing source fire area, particularly under strong winds and in areas containing dense forest and steep slopes. General vegetation descriptors better predicted spotting compared with bark hazard and presence variables, suggesting systems that measure and map bark spotting potential need improvement. The results from this study have important implications for the development of predictive spotting and wildfire behaviour models.

}, keywords = {Fire behaviour, line scan, spot fire}, doi = {https://doi.org/10.1071/WF19124}, url = {https://www.publish.csiro.au/wf/WF19124}, author = {Michael Storey and Owen Price and Jason J. Sharples and Ross Bradstock} } @article {bnh-7475, title = {Exploring the key drivers of forest flammability in wet eucalypt forests using expert-derived conceptual models}, journal = {Landscape Ecology}, volume = {35}, year = {2020}, month = {06/2020}, pages = {1775{\textendash}1798}, abstract = {

Context

Fire behaviour research has largely focused on dry ecosystems that burn frequently, with far less attention on wetter forests. Yet, the impacts of fire in wet forests can be high and therefore understanding the drivers of fire in these\ systems\ is vital.

Objectives

We sought to identify and rank by importance the factors plausibly driving flammability in wet eucalypt forests, and describe relationships between them. In doing so, we formulated a set of research priorities.

Methods

Conceptual models of forest flammability in wet eucalypt forests were elicited from 21 fire experts using a combination of elicitation techniques. Forest flammability was defined using fire occurrence and fireline intensity as measures of ignitability and heat release rate, respectively.

Results

There were shared and divergent opinions about the drivers of flammability in wet eucalypt forests. Widely agreed factors were drought, dead fine fuel moisture content, weather and topography. These factors all influence the availability of biomass to burn, albeit their effects and interactions on various dimensions of flammability are poorly understood. Differences between the models related to lesser understood factors (e.g. live and coarse fuel moisture, plant traits, heatwaves) and the links between factors.

Conclusions

By documenting alternative conceptual models, we made shared and divergent opinions explicit about flammability in wet forests. We identified four priority research areas: (1) quantifying drought and fuel moisture thresholds for fire occurrence and intensity, (2) modelling microclimate in dense vegetation and rugged terrain, (3) determining the attributes of live vegetation that influence forest flammability, (4) evaluating fire management strategies.

}, keywords = {Cognitive mapping, Conceptual models, Expert elicitation, Fire behaviour, fire intensity, flammability, Structured decision-making, Structured expert judgement, Wet forest, Wildfire}, doi = {https://doi.org/10.1007/s10980-020-01055-z}, url = {https://link.springer.com/article/10.1007/s10980-020-01055-z}, author = {Jane Cawson and Victoria Hemming and Ackland, A and Wendy R. Anderson and David Bowman and Ross Bradstock and Brown, T and Jamie Burton and Geoffrey J. Cary and Thomas Duff and Alex Filkov and Furlaud, James M. and Tim Gazzard and Kilinc, Musa and Petter Nyman and Ross Peacock and Mike Ryan and Jason J. Sharples and Gary J. Sheridan and Tolhurst, K.G. and Tim Wells and Phil Zylstra and Trent Penman} } @article {bnh-7495, title = {Fire coalescence and mass spot fire dynamics: experimentation, modelling and simulation {\textendash} annual project report 2019-2020}, number = {625}, year = {2020}, month = {11/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {MELBOURNE}, abstract = {

This report outlines the progress of the Fire Coalescence and Mass Spot Fire Dynamics project, which is one of the projects within the Next Generation Fire Modelling cluster. Specifically, the report summarises progress of the first two years of the second phase of the project, which has been extended over 2018-2021.

All milestones from the 2015-2018 phase of the project have now been delivered, and the project is continuing to build upon this work in delivering important insights into the dynamics of fire behaviour and fire line interaction. Phase 2 of the experimental program is in progress, and will extend recently published work from Phase 1. The project continues to yield important and significant insights into the behaviour of coalescing fires, and these insights are enhancing our understanding of the processes driving fire propagation and the way we model dynamic fire behaviours. \ 

In particular, the research has continued to develop the pyrogenic potential model by incorporating firebrand dynamics. This has resulted in the world{\textquoteright}s first capability to model dynamic modes of fire propagation such as vorticity-driven lateral spread using a two-dimensional simulation framework with a spotting module. This means that explicitly modelling such effects in operational timeframes is now a feasible option. The research has also examined how wind-terrain interaction influences ember trajectories and the likely distribution of spot fires down wind of complex terrain.

In the past year, the project team have delivered a number of research outputs, including conference presentations and posters and journal publications. Still more publications are in preparation. The project team has also delivered on a number of key utilisation activities. These have mainly involved discussions with key end users about the prospects of the research being incorporated into education materials and training resources for firefighters and fire behaviour analysts. The project has also begun working on a dedicated utilisation project aimed at development of spot fire spatial mapping tools.

After providing some background information on the project{\textquoteright}s aims and methodology, this report provides details on the progress of the project to date. In particular, this includes:

At the time of writing, the project is on-schedule.

}, keywords = {experimentation, fire coalescence, mass spot fire dynamics, modelling, simulation}, issn = {625}, author = {Jason J. Sharples and James Hilton and Sullivan, Andrew and Badlan, R} } @article {bnh-6811, title = {Fire coalescence and mass spot fire dynamics: experimentation, modelling and simulation - Annual project report 2018-2019}, number = {559}, year = {2020}, month = {03/2020}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

This report outlines the progress of the Fire Coalescence and Mass Spot Fire Dynamics project, which is one of the projects within the Next Generation Fire Modelling cluster. Specifically, the report summarises progress of the first year of the second phase of the project, which has been extended over 2018-2021.

All milestones from the 2015-2018 phase of the project have now been delivered, and the project is continuing to build upon this work in delivering important insights into the dynamics of fire behaviour and fire line interaction. Phase 2 of the experimental program is in progress, and will extend recently published work from Phase 1. The project continues to yield important and significant insights into the behaviour of coalescing fires, and these insights are enhancing our understanding of the processes driving fire propagation and the way we model dynamic fire behaviours. \ 

In particular, the research has continued to develop the pyrogenic potential model by incorporating the effects of pyrogenic vorticity. This has resulted in the world{\textquoteright}s first capability to model dynamic modes of fire propagation such as vorticity-driven lateral spread using a two-dimensional simulation framework. This means that explicitly modelling such effects in operational timeframes is now a feasible option. Coupled fire-atmosphere simulations continue to provide fundamental insights that will be drawn upon to inform further the development of the pyrogenic potential model.

In the past year, the project team have delivered a number of research outputs, including conference presentations and posters and a journal publication (currently under review). A number of other publications are in preparation. The project team has also delivered on a number of key utilisation activities. These have mainly involved discussions with key end-users about the prospects of the research being incorporated into education materials and training resources for firefighters and fire behaviour analysts.

After providing some background information on the project{\textquoteright}s aims and methodology, this report provides details on the progress of the project to date. In particular, this includes:

At the time of writing, the project is on schedule.

}, keywords = {experimentation, fire coalescence, modelling, simulation, spot fire dynamics}, issn = {559}, author = {Jason J. Sharples and James Hilton and Sullivan, Andrew} } @article {bnh-7944, title = {Intensifying Australian heatwave trends and their sensitivity to observational data}, journal = {Earth{\textquoteright}s Future}, year = {2020}, month = {12/2020}, abstract = {

Heatwaves are an accustomed extreme event of the Australian climate, which can cause catastrophic impacts on human health, agriculture, and urban and natural systems. We have analysed the trends in Australia-wide heatwave metrics (frequency, duration, intensity, number, cumulative magnitude, timing, and season duration) across 69 extended summer seasons (i.e., from Nov-1951 to Mar-2020). Our findings not only emphasise that heatwaves are becoming hotter, longer, and more frequent, but also signify that they are occurring with excess heat, commencing much earlier, and expanding their season over many parts of Australia in recent decades. The Australian heatwave trends have strengthened since last observed Australian study was conducted. We also investigated the heatwave and severe heatwave trends at a local city-scale using three different observational products (AWAP and SILO gridded datasets and ACORN_SATV2 station data) over selected time periods (1911-2019, 1911-64, and 1965-2019). Results suggest that heatwave trends are noticeably different amongst the three datasets. However, the results highlight that the severe heatwave cumulative magnitude and their season duration have been increasing significantly in recent decades over Australia{\textquoteright}s southern coastal cities (like Melbourne and Adelaide). The climatological mean of the most heatwave and severe heatwave metrics is substantially higher in recent decades compared to earlier periods across all the cities considered. The findings of our study have significant implications for the development of advanced heatwave planning and adaptation strategies.

}, keywords = {Australia, Climate change, heatwaves, urban}, doi = {10.1002/essoar.10505178.1 }, url = {https://www.essoar.org/doi/10.1002/essoar.10505178.1}, author = {P Jyoteeshkumar reddy and Sarah Perkins-Kirkpatrick and Jason J. Sharples} } @article {bnh-6736, title = {Modeling Vorticity-Driven Wildfire Behavior Using Near-Field Techniques}, journal = {Frontiers in Mechanical Engineering}, year = {2020}, month = {01/2020}, abstract = {

Dynamic modes of fire propagation present a significant challenge for operational fire spread simulation. Current two-dimensional operational fire simulation platforms are not generally able to account for the complex interactions that drive such behaviors, and while fully coupled fire-atmosphere models are able to account for dynamic effects to an extent, their computational demands are prohibitive in an operational context. In this paper we consider techniques for extending two-dimensional fire spread simulators so that they are able to simulate certain dynamic fire behaviors. In particular, we consider modeling vorticity-driven lateral spread (VLS), which is characterized by rapid lateral fire propagation across steep, leeward slopes. Specifically, we consider modeling the influence of the fire on the local surface airflow via a {\textquotedblleft}pyrogenic potential{\textquotedblright} model, which allows for vertical vorticity effects (in a near-field sense) using the Helmholtz decomposition. The ability of the resulting model to emulate fire propagation associated with VLS is demonstrated using a number of examples.

}, keywords = {Fire, fire-atmosphere, modelling, vorticity-driven lateral spread}, doi = {https://doi.org/10.3389/fmech.2019.00069}, url = {https://www.frontiersin.org/articles/10.3389/fmech.2019.00069/full}, author = {Jason J. Sharples and James Hilton} } @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-7242, title = {The effect of ignition protocol on grassfire development}, journal = {International Journal of Wildland Fire}, volume = {29}, year = {2019}, month = {11/2019}, pages = {70-80}, abstract = {

The effect of ignition protocol on the development of grassfires is investigated using physics-based simulation. Simulation allows measurement of the forward rate of spread of a fire as a function of time at high temporal resolution. Two ignition protocols are considered: the inward ignition protocol, where the ignition proceeds in a straight line from the edges of the burnable fire plot to the centre of the plot; and the outwards ignition protocol, where the ignition proceeds from the centre of the burnable fire plot to the edges of the plot. In addition to the two ignition protocols, the wind speed, time taken for the ignition to be completed and ignition line length are varied. The rate of spread (R) of the resultant fires is analysed. The outwards ignition protocol leads to an (approximately) monotonic increase in\ R, whereas the inward ignition protocol can lead to a peak in\ R\ before decreasing to the quasi-equilibrium\ R. The fires simulated here typically take 50 m from the ignition line to develop a quasi-equilibrium\ R. The results suggest that a faster ignition is preferable to achieve a quasi-equilibrium\ R\ in the shortest distance from the ignition line.

}, keywords = {grassfire, ignition, physics simulation}, doi = {https://doi.org/10.1071/WF19046}, url = {https://www.publish.csiro.au/WF/WF19046}, author = {Duncan Sutherland and Jason J. Sharples and Khalid Moinuddin} } @article {bnh-6392, title = {Evolution of an extreme Pyrocumulonimbus-driven wildfire event in Tasmania, Australia}, journal = {Natural Hazards and Earth System Sciences}, year = {2019}, month = {12/2019}, abstract = {

Extreme fires have substantial adverse effects on society and natural ecosystems. Such events can be associated with intense coupling of fire behaviour with the atmosphere, resulting in extreme fire characteristics such as pyrocumulonimbuscloud (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-minute 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, 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-minute period in the afternoon of 4 January, with the cloud top reaching a height of 15 km. The pyroCb was associated with a highly unstable atmosphere (C-Haines 10-11) and Severe-marginally Extreme (FFDI 60-75) near-surface fire weather, and 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 2007-2016 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 highlight the vulnerability of southeast Tasmania to extreme fire events.

}, keywords = {C-Haines, extreme fire, fire severity, Fire weather, McArthur Forest Fire Danger Index, pyrocumulonimbus, smoke plume injection, Tasmania, wildland fire}, doi = {https://doi.org/10.5194/nhess-2019-354}, url = {https://www.nat-hazards-earth-syst-sci-discuss.net/nhess-2019-354/}, author = {Mercy Ndalila and Grant Williamson and Paul Fox-Hughes and Jason J. Sharples and David Bowman} } @conference {bnh-6292, title = {Incorporating firebrands and spot fires into vorticity-driven wildfire behaviour models}, booktitle = {23rd International Congress on Modelling and Simulation}, year = {2019}, month = {12/2019}, abstract = {

Complex modes of fire behaviour resulting from local coupling between the fire and the atmosphere are a significant challenge for rapid operational wildfire spread simulations. While threedimensional fully coupled fire-atmosphere models are able to account for many types of fire behaviour, their computational demands are prohibitive in an operational context. Two-dimensional fire spread models have much lower computational overhead, but are generally not able to account for complex local coupling effects and cannot provide a three-dimensional flow structure suitable for modelling the transport of firebrands. In this paper we investigate extending two-dimensional fire spread simulations to model local coupling effects resulting from wind flow over a ridge that can result in a number of non-intuitive modes of fire behaviour. These include fire propagation opposite to the direction of the prevailing wind on the lee slope of ridges caused by re-circulation on the lee slope, called vorticity-driven lateral spread (VLS). Furthermore we develop extensions of these two-dimensional models to incorporate three-dimensional firebrand transport and show that enhanced downwind spot fire formation can result under certain VLS conditions.

The spread of fires under VLS conditions is driven by vortices in the ground plane. A model for the production and effects of these vortices was incorporated into computational simulations using a vector potential formu-lation in similar manner to a scalar {\textquoteleft}pyrogenic potential{\textquoteright} model, detailed in earlier studies. Firebrands were incorporated using a Lagrangian scheme to model transport through the atmosphere and a sub-scale model for spot fire creation and growth. The firebrand transport took factors such as drag, gravity and buoyancy into account. As effect of plume buoyancy on firebrands under real-world conditions for this scenario is currently unknown, the plume buoyancy was parameterised using a exponential decay model. The sensitivity of the decay parameter in this model was then examined in relation to the resulting spot fire distribution and area burnt. All simulations were carried out using Spark, a wildfire prediction framework.

The coupled VLS and firebrand transport simulations indicated that a higher value of decay parameter, rep-resenting a higher cooling rate of the plume, acted to enhance the lateral spread as firebrands were lofted for shorter times and were caught in the vortices at the edge of the lateral spread region. In contrast, a lower value of decay parameter, representing a lower cooling of the plume, resulted in widespread downwind spot fires and larger burnt areas. This appeared to be due to longer lofting times resulting in firebrands being transported further downwind and away from the vortices within the lateral spread region. The model appears, at least qualitatively, to match observed lateral spread and {\textquoteright}deep flaming{\textquoteright} fire behaviour although many of the parame-ters in the model require further research and experimental calibration. Further development of the model may allow these complex modes

}, keywords = {dynamic fire propagation, embers, Firebrands, spotting, wildfire simulation}, doi = {https://doi.org/10.36334/modsim.2019.H7.hilton2}, url = {https://mssanz.org.au/modsim2019/H7/hilton2.pdf}, author = {James Hilton and Garg, N and Jason J. Sharples} } @article {bnh-5376, title = {Modelling wind direction distributions using a diagnostic model in the context of probabilistic fire spread prediction}, journal = {Frontiers in Mechanical Engineering: Thermal and Mass Transport}, year = {2019}, month = {02/2019}, abstract = {

With emerging research into the dynamics of extreme fire behaviour, it is increasingly important for wind models used in operational fire prediction to accurately capture areas of complex flow across rugged terrain. Additionally, the emergence of ensemble and stochastic modelling frameworks has led to the discussion of uncertainty in fire prediction. To capture the uncertainty of modelled fire outputs, it is necessary to recast uncertain inputs in probabilistic terms.\ 

WindNinja is the diagnostic wind model currently applied within a number of operational fire prediction frameworks across the world. For computational efficiency, allowing for real-time or faster than real-time prediction, the physical equations governing wind flow across complex terrain are often simplified. The model has a number of well documented limitations, for instance, it is known to perform least well on leeward slopes. This study first aims to understand these limitations in a probabilistic context by comparing individual deterministic predictions to observed distributions of wind direction. Secondly, a novel application of the deterministic WindNinja model is presented and shown to enable prediction of wind direction distributions that capture some of the variability of complex wind flow.\ 

Recasting wind fields in terms of probability distributions enables better understanding of variability across the landscape, and provides the probabilistic information required to capture uncertainty through ensemble or stochastic fire modelling. The comparisons detailed in this study indicate the potential for WindNinja to predict multimodal wind direction distributions that represent complex wind behaviours, including recirculation regions on leeward slopes. However, the limitations of using deterministic models within probabilistic frameworks are also highlighted. To enhance fire prediction and better understand uncertainty, it is recommended that statistical approaches also be developed to complement existing physics-based deterministic wind models.

}, keywords = {complex terrain, deterministic, ensemble modelling, Probability distributions, uncertainty, von Mises, wind modelling, WindNinja}, doi = {10.3389/fmech.2019.00005}, url = {https://www.frontiersin.org/articles/10.3389/fmech.2019.00005/abstract}, author = {Rachael Quill and Jason J. Sharples and Natalie Wagenbrenner and Leesa Sidhu and Jason Forthofer} } @article {bnh-5771, title = {A Statistical Approach to Understanding Canopy Winds over Complex Terrain}, journal = {Environmental Modeling \& Assessment}, year = {2019}, month = {08/2019}, pages = {1-20}, abstract = {

Winds that flow within a forest canopy in complex terrain exhibit considerable variability that can have significant consequences for environmental processes such as the spread of bushfires, seed dispersal and transport of pollutants. This variability is still poorly understood, due in part to limited observations of canopy winds over complex terrain, and as such is often unaccounted for in deterministic modelling approaches. Probabilistic representation of wind fields can better characterise variability and build understanding of uncertainty in applications such as bushfire prediction. This study introduces two new, publicly available, datasets that support analyses of canopy winds over complex terrain using novel statistical approaches. Wind fields are characterised using bivariate distributions, representing the response of synoptic winds to changing landscapes, including post-bushfire forest regrowth and varying topography across uniform vegetation. For statistical comparison, non-parametric Kolmogorov-Smirnov style tests are considered. A new test is proposed for the comparison of bivariate circular distributions arising from analyses of wind direction. The study broadly reaffirms established theory while highlighting the variability of canopy winds over complex terrain and the importance of developing statistical techniques that result in a better quantitative understanding of these wind fields and the processes driving them.

}, keywords = {Circular statistics, Flow separation, forest canopy, uncertainty, Wind field observations, wind modelling}, doi = {https://doi.org/10.1007/s10666-019-09674-w}, url = {https://link.springer.com/article/10.1007/s10666-019-09674-w}, author = {Rachael Quill and Jason J. Sharples and Leesa Sidhu} } @conference {bnh-6291, title = {Wind-terrain effects on firebrand dynamics}, booktitle = {23rd International Congress on modelling and Simulation}, year = {2019}, month = {12/2019}, abstract = {

Despite its importance in bushfire propagation, firebrand transport and the spotting process are still poorly understood, and there is no definitive model that can adequately emulate the spotting process in general. The dynamics of firebrands are difficult to predict due to the complex flow structure resulting from the interaction of a buoyant plume with a boundary layer wind field. Understanding the nature of this flow structure, especially for complex terrain, is essential for determining the likely path of firebrands and subsequent distributions of new spot fires and risk levels on structures downwind from the fire.

Although several prior computational modelling studies have carried out investigations of firebrand transport, the effect of the terrain has not previously been taken into account. It is well known that topography can significantly affect ember generation. For example, the enhanced intensity of a fire running up a steep slope can generate a large number of embers. More generally, terrain-modified flows and the strong turbulence associated with leeward slopes and flow around other prominent topographic features may have a pronounced effect on the transport of firebrands. Moreover, modes of dynamic fire propagation such as vorticity-driven lateral spread and eruptive fire spread in canyons involve a coupling between the fire, the terrain and the prevailing winds and so can affect the rate at which firebrands are produced as well as their subsequent transport.

In this study we use a coupled computational fluid dynamic (CFD) and Lagrangian particle approach to model the transport of firebrands. The model is applied to two different terrain scenarios to investigate the flow dynamics, firebrand trajectories and landing patterns resulting from the interaction with the terrain. The first scenario is a line of fire on the lee slope of a ridge burning perpendicular to an incident wind flow. The second scenario is a fire burning in a canyon aligned with the wind. The simulations indicate that the addition of terrain adds a further level of complexity to the flows generated by interaction between the wind and the fire. The terrain appears to modify the counter-rotating vortex pair in the plume structure. For the fire in the lee of the ridge line, the wind-terrain interaction resulted in a flattening and tilting of the counter-rotating vortex pair and enhanced regions of recirculation at the edges of the fire, which were conducive to lateral transport of embers. For the fire in the canyon, the channelling of the winds up the canyon resulted in the formation of a single jet-like vortex transporting firebrands upwards and over the top of the canyon. We hypothesise that this effect is caused by the shape and alignment of the canyon, which forces the vortex pair to merge into a single vortex.

}, keywords = {Climate change, Hydrograph model, parametrization, precipitation, runoff formation processes}, doi = {https://doi.org/10.36334/modsim.2019.H7.hilton}, url = {https://mssanz.org.au/modsim2019/H7/hilton.pdf}, author = {James Hilton and Jason J. Sharples and Garg, N and Murray Rudman and Swedosh, W and Commins, D} } @article {bnh-4427, title = {Analysis of the physical processes associated with junction fires at laboratory and field scales}, journal = {International Journal of Wildland Fire }, volume = {27}, year = {2018}, month = {01/2018}, abstract = {

Junction fires, which involve the merging of two linear fire fronts intersecting at a small angle, are associated with very intense fire behaviour. The dynamic displacement of the intersection point of the two lines and the flow along the symmetry plane of the fire are analysed for symmetric boundary conditions. It is observed that the velocity of displacement of this point increases very rapidly owing to strong convective effects created by the fire that are similar to those of an eruptive fire. The change of fire geometry and of its associated flow gradually blocks the rate of spread increase and creates a strong deceleration of the fire, which ends up behaving like a linear fire front. Results from laboratory and field-scale experiments, using various fuel beds and slope angles and from a large-scale fire show that the processes are similar at a wide range of scales with little dependence on the initial boundary conditions. Numerical simulation of the heat flux from two flame surfaces to an element of the fuel bed show that radiation can be considered as the main mechanism of fire spread only during the deceleration phase of the fire.

}, keywords = {accelerating fires, convective effects, dynamic fire behaviour, extreme fire behaviour, Fire behaviour, merging fires.}, doi = {10.1071/WF16173}, url = {http://www.publish.csiro.au/WF/WF16173}, author = {J. R. Raposo and D. X. Viegas and X. Xie and M. Almeida and A. R. Figueiredo and L. Porto and Jason J. Sharples} } @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} } @article {bnh-5194, title = {How do weather and terrain contribute to firefighter entrapments in Australia?}, journal = {International Journal of Wildland Fire}, volume = {27}, year = {2018}, month = {02/2018}, pages = {85-98}, chapter = {85}, abstract = {

Adverse weather conditions and topographic influences are suspected to be responsible for most entrapments of firefighters in Australia. A lack of temporally and spatially coherent set of data however, hinders a clear understanding of the contribution of each weather type or terrain driver on these events. We investigate coronial inquiries and internal fire agencies reports across several Australian states from 1980 to 2017 and retrieve 45 entrapments. A first analysis reveals that most entrapments happen during large fires and that the number of deaths has decreased over the last few decades. Comparing the meteorological and topographical conditions of the entrapments with the conditions of a reference set of fires without entrapment, we build a linear regression model that identifies the main contributors to firefighter entrapment. A change in wind direction, which was associated with 42\% of the incidents examined, is the main factor contributing to entrapments. Interaction between strong winds and steep slopes also influences the likelihood of entrapment and suggests that dynamic fire behaviours may also play important roles. As further details of this relationship between dynamic fire propagation and firefighter entrapment is now required, the understanding of weather and terrain contribution is a first step to produce comprehensive safety guidance.

}, doi = {https://doi.org/10.1071/WF17114}, url = {https://www.publish.csiro.au/WF/WF17114}, author = {Lahaye, S and Jason J. Sharples and Stuart Matthews and Heemstra, S and Owen Price and Badlan, R} } @article {bnh-5192, title = {Incorporating convective feedback in wildfire simulations using pyrogenic potential}, journal = {Environmental Modelling \& Software}, volume = {107}, year = {2018}, month = {09/2018}, pages = {12-24}, chapter = {12}, abstract = {

Modelling the dynamics of wildfires is very computationally challenging. Although three-dimensional\ computational fluid dynamics\ (CFD) models have been successfully applied to wildfires, the\ computational time\ required makes them currently impractical for operational usage. In this study, we develop a two-dimensional\ propagation model\ coupled to a {\textquoteleft}pyrogenic{\textquoteright}\ potential flowformulation representing the inflow of air generated by the fire. This model can accurately replicate features of fires previously unable to be simulated using current\ two-dimensional models, including development of a fire line into a parabolic shape, attraction between nearby fires and the observed closing behaviour of {\textquoteleft}V{\textquoteright} shaped fires. The model is compared to\ experimental resultswith good agreement. The pyrogenic potential model is orders of magnitude faster than a full\ CFD\ model, and could be used for improved operational wildfire prediction.

}, doi = {https://doi.org/10.1016/j.envsoft.2018.05.009}, url = {https://www.sciencedirect.com/science/article/pii/S1364815217309593}, author = {James Hilton and Sullivan, Andrew and Swedosh, W and Jason J. Sharples and Christopher Thomas} } @conference {bnh-5024, title = {Pyroconvective interactions and dynamic fire propagation}, booktitle = {AFAC18}, year = {2018}, month = {09/2018}, address = {Perth}, abstract = {

Modelling the dynamic propagation of wildfires remains a significant challenge. Pyroconvective interactions between the fire and the atmosphere, or between different parts of the fire itself, can produce distinctly non-steady modes of fire propagation that cannot be accounted for using current operational models.


While sophisticated three-dimensional models (e.g. computational fluid dynamics (CFD) models or coupled fire-atmosphere models) have been successfully applied to wildfires, their computational requirements render them impractical for operational usage.


Here we discuss a computationally efficient two-dimensional propagation model, which can accurately replicate dynamic features of fire spread that cannot be simulated using existing two-dimensional models. These features include the development of a wind-driven fire line into a parabolic shape, attraction between nearby fires and the observed closing behaviour of junction fires. The model is compared to experimental results with good agreement.
The model incorporates a simple sub-model to account for the inflow of air generated by a fire, which allows the model to run orders of magnitude faster than full physical models, while still capturing many of the essential features of dynamic fire propagation. We argue that such a model could lead to significant improvements in operational wildfire prediction.
In addition, we will highlight some recent insights in to how the geometry of a fire line and the flaming zone influences development of the pyroconvective plume above a fire. In particular, we present evidence that the geometry of the burning region can affect plume development in a way that is comparable to the effect of total energy release.

}, author = {James Hilton and Badlan, R and Sullivan, Andrew and Swedosh, W and Thomas, C. M. and Jason J. Sharples} } @article {bnh-5193, title = {What are the drivers of dangerous fires in Mediterranean France?}, journal = {International Journal of Wildland Fire}, volume = {27}, year = {2018}, month = {03/2018}, pages = {155-163}, chapter = {155}, abstract = {

Wildfire containment is often very challenging for firefighters, especially for large and rapidly spreading fires where the risk of firefighter entrapment is high. However, the conditions leading to these {\textquoteleft}dangerous{\textquoteright} fires are poorly understood in Mediterranean Europe. Here, we analyse reports and interviews of firefighters over the last 40 years in four regions of south-eastern France and investigate the weather conditions that induce large fires, fast-growing fires and fires that are conducive to entrapment. We adopt a quantile regression model to test the effect of weather conditions across different fire sizes and growth rates. The results show that strong winds drive the largest fires everywhere except in Corsica, the southernmost region, where high temperature is the main driver. Strong winds also drive entrapments whereas high temperatures induce rapidly spreading fires. This emphasises that wind-driven fire is the dominant pattern of dangerous fires in France, but it reveals that large {\textquoteleft}convective{\textquoteright} fires can also present considerable danger. Beyond that, the Fire Weather Index appears to be a good predictor of large fires and fires conducive to entrapments. Identifying weather conditions that drive {\textquoteleft}dangerous{\textquoteright} wildfires will provide useful information for fire agencies to better prepare for adverse fire behaviours.

}, doi = {10.1071/WF17087}, url = {http://www.publish.csiro.au/wf/WF17087}, author = {Lahaye, S and Curt, T and Fr{\'e}javille, T and Jason J. Sharples and Paradis, L and H{\'e}ly, C} } @article {bnh-4205, title = {Fire coalescence and mass spotfire dynamics - experimentation, modelling and simulation: annual project report 2016-17}, number = {312}, year = {2017}, month = {09/2017}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

This report outlines the progress of the Fire Coalescence and Mass Spot Fire Dynamics project, which is one of the projects within the Next Generation Fire Modelling cluster.

The project has now been running for approximately 2.4 years. Phase 1 of the experimental program has now been completed and initial results are in the process of being published. Phase 2 of the experimental program is being considered. The project has continued to yield important and significant insights into the behaviour of coalescing fires, and these insights have broader implications for our understanding of the processes driving fire propagation and the way we model dynamic fire behaviours. \ 

In particular, the research has continued to address the role that fire line geometry plays in the dynamic propagation of wildfires. The project team has identified a number of circumstances where the curvature-based models that they previously developed do not provide accurate simulation. This included a number of the particular experimental scenarios considered in Phase 1 of the experimental program. However, coupled fire-atmosphere simulations provided a number of fundamental insights that motivated the development of more broadly applicable two-dimensional models.\  These new models are able to explain why the curvature-based models worked when they did, and are able to provide accurate predictions in a broader number of circumstances, including those for which the curvature-based models had failed. \ 

At this stage the project has published three journal papers and three conference papers. Three more journal papers and four more peer-reviewed conference papers are in the final stages of preparation. Several conference posters have also been produced. In addition, the project team has delivered a significant number of presentations to stakeholders and researchers

After providing some background information on the project{\textquoteright}s aims and methodology, this report provides details on the progress of the project to date. In particular this includes:

At the time of writing, the project is several months behind schedule. However, the project team is confident that all milestones will be successfully delivered along with a number of unscheduled, yet significant research outputs.

}, issn = {312}, author = {Jason J. Sharples and James Hilton and Sullivan, Andrew} } @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} } @conference {bnh-3907, title = {A unified approach to fire spread modelling}, booktitle = {AFAC17}, year = {2017}, month = {09/2017}, publisher = {Bushfire and Natural Hazards CRC}, organization = {Bushfire and Natural Hazards CRC}, address = {Sydney}, abstract = {

One of the main goals of bushfire research is to provide a relatively simple and timely answer to the question {\textquotedblleft}What is the fires{\textquoteright} forward rate of spread?{\textquotedblright} Indeed, pursuit of such an answer has engaged some of the brightest minds in wildland fire science, and has produced a variety of fire spread models that apply across a number of common vegetation or fuel types. In Australia, these models date back to the 1950s-60s, with the work of Alan McArthur, and extend through to the current day with the most recent developments in shrubland fire spread models and refinements to the curing function in the CSIRO grassland fire spread model. In the present work we consider the way that meteorological factors are incorporated into the suite of existing fire spread models, which encompass a variety of different fuel types, and discuss an approach that unifies their inclusion. The utility of this unified modelling approach is demonstrated via model comparison using real meteorological data over a range of vegetation types. In particular, we demonstrate that the meteorological (i.e. non-fuel) sub-models of the current suite of operational models, which are of many and varied functional form, can be replaced by a single, unified, two-parameter model, with no appreciable loss in model performance. The unified model has the distinct advantage of being conceptually straightforward and extremely parsimonious compared to current operational approaches. The existence of a simple, yet effective, unified approach to fire spread modelling has implications for initiatives such as the National Fire Danger Rating project, as it establishes a common modelling basis that can be applied to the many different fuel types that are encountered across the nation.

}, author = {Jason J. Sharples} } @conference {bnh-4333, title = {What are the safety implications of dynamic fire behaviours?}, booktitle = {22nd International Congress on Modelling and Simulation}, year = {2017}, month = {12/2017}, address = {Hobart}, abstract = {

Many firefighters in the world have been injured or killed due to a forest fire entrapment, caught by the fire heat or smoke. Some case studies have pointed out that dynamic fire behaviour may have played a role. We investigate here how changes in wind direction, channelling (i.e. vorticity-driven lateral spread on a leeward slope) and long distance spotting could contribute to entrapments through a process model, simplified in Figure 1. There are three situations likely to entrap firefighters:

We review fire agencies archives in Australasia and Europe from 1979 to 2017 and retrieve 106 entrapments, investigating weather, terrain and location of fire front during entrapment. We also compare the Australasian subset with fires without entrapment using a binomial regression function.

In Australia, changes in wind direction induced by cold front passes is the main factor contributing to entrapment. These sudden changes in wind direction switch long smooth burning flanks of fire in violent fronts and lead to S1 situations. S2, sudden lateral spread, occurs in rough terrain. There, leeward slopes may generate channelling, causing entrapment several hundred meters far away from the fire flank. S3 appears when fire danger index reaches highest values. When fuel drought combines with adverse weather conditions, mass spotting propagates fire at long distance. Then, firefighters may be entrapped whatever the terrain.

This work improves our understanding of the process from dynamic fire behaviour to firefighter entrapment. Identifying three different situations, the model should help fire agencies to adapt their safety warnings regarding the local daily conditions.

}, author = {Lahave, S and Jason J. Sharples and Stuart Matthews and Heemstra, S and Owen Price} } @article {bnh-3186, title = {Curvature effects in the dynamic propagation of wildfires}, journal = {International Journal of Wildland Fire}, volume = {25}, year = {2016}, month = {10/2016}, abstract = {

The behaviour and spread of a wildfire are driven by a range of processes including convection, radiation and the transport of burning material. The combination of these processes and their interactions with environmental conditions govern the evolution of a fire{\textquoteright}s perimeter, which can include dynamic variation in the shape and the rate of spread of the fire. It is difficult to fully parametrise the complex interactions between these processes in order to predict a fire{\textquoteright}s behaviour. We investigate whether the local curvature of a fire perimeter, defined as the interface between burnt and unburnt regions, can be used to model the dynamic evolution of a wildfire{\textquoteright}s progression. We find that incorporation of curvature dependence in an empirical fire propagation model provides closer agreement with the observed evolution of field-based experimental fires than without curvature dependence. The local curvature parameter may represent compounded radiation and convective effects near the flame zone of a fire. Our findings provide a means to incorporate these effects in a computationally efficient way and may lead to improved prediction capability for empirical models of rate of spread and other fire behaviour characteristics.

}, url = {http://www.publish.csiro.au/WF/WF16070}, author = {James Hilton and Jason J. Sharples and Sullivan, Andrew} } @article {bnh-2971, title = {Fire coalescence and mass spot fire dynamics: experimentation, modelling and simulation: Annual project report 2015-2016}, number = {171}, year = {2016}, month = {09/2016}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

This report outlines the progress of the Fire Coalescence and Mass Spot Fire Dynamics project, which is one of the projects within the Next Generation Fire Modelling cluster.
The project has now been running for approximately 15 months. The Science Plan has been finalized and the Advisory Committee has been settled. The experimental program is now up and running after a few initial delays caused by issues with sourcing adequate fuel and with development of experimental apparatus. The modelling and simulation aspects of the project have made a number of significant fire spread modelling developments and have made strong contributions to our understanding of the processes driving fire coalescence and dynamic fire spread more generally.\ In particular, the research has addressed the role that fire line geometry (especially curvature) plays in the dynamic propagation of wildfires. The project team has demonstrated that fire propagation models incorporating curvature dependence can out-perform quasi-steady (first-order) models when applied to simple wind-driven fires at both laboratory and field scales.


In addition, the research has produced a number of fundamental insights into how the shape of the fire line can affect the pyroconvective interactions between different parts of a fire. These insights have mostly been gained by targeted simulations using a coupled fire-atmosphere model.
At this stage the project has published two conference papers (one peer reviewed), and two conference posters. There are currently three journal papers submitted to international peer-reviewed journals with another one in the final stages of preparation. In addition, the project team has delivered thirteen presentations and posters to stakeholders and researchers.\ After providing some background information on the project{\textquoteright}s aims and methodology, this report provides details on the progress of the project to date. In particular this includes:

At the time of writing, the project is on schedule. The project team is confident that all milestones will be successfully delivered along with a number of unscheduled, yet significant research outputs.

}, issn = {171}, author = {Jason J. Sharples and James Hilton and Sullivan, Andrew} } @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} } @conference {bnh-2932, title = {Wind speed reduction induced by post-fire vegetation regrowth}, booktitle = {AFAC16}, year = {2016}, month = {08/2016}, publisher = {Bushfire and Natural Hazards CRC}, organization = {Bushfire and Natural Hazards CRC}, address = {Brisbane}, abstract = {

In the current suite of operational fire spread models, wind speeds measured in the open environment (above the vegetation layer) are modified to represent wind speeds at {\textquoteleft}mid-flame{\textquoteright} height using adjustment factors. In general, these adjustment factors assume constant vertical wind speed profiles throughout the vegetation layer. However, empirical studies have shown that wind speeds beneath canopies can vary significantly with height above ground as well as with forest type and prevailing wind speed. Empirical wind reduction profiles have been developed for a number of different forest types in flat terrain using data collected across Victoria, Australia.


The present research aims to extend these empirical studies to better understand the impacts of topography and post-fire vegetation regrowth on the reduction of wind speeds beneath the canopy. Wind data collected over fire affected regions of rugged terrain in South Eastern Australia are used to analyse wind speed reduction induced by post-fire regrowth and complex topography. A secondary study is used to analyse wind speed reduction caused by Radiata pine plantation in undulating terrain.


Results of this study suggest that empirical wind reduction profiles perform well at the broader landscape-scale, i.e. ridge tops and valley floors. However, more complex topographical features appear to have a compounding affect on wind speed reduction within rugged terrain. Through better understanding of wind speed reduction beneath the canopy across landscapes from mountainous ranges through to flat plains, wind speed reduction models for bushfire spread prediction can be adapted to incorporate the variation observed in vertical wind speed profiles within the vegetation layer.

}, author = {Rachael Quill and Kangmin Moon and Jason J. Sharples and Leesa Sidhu and Thomas Duff and Tolhurst, K.G.} } @article {bnh-2394, title = {Dynamic modelling of fire coalescence}, year = {2015}, author = {Jason J. Sharples and James Hilton and Sullivan, Andrew} } @article {bnh-2339, title = {Fire coalescence and mass spotfire dynamics: Experimentation, modelling and simulation - Annual project report 2014-2015}, number = {129}, year = {2015}, month = {02/11/205}, institution = {Bushfire and Natural Hazards CRC}, address = {Melbourne}, abstract = {

Fire behaviour in dry eucalypt forests in Australia (and in many other vegetation types to a lesser extent) is characterised by the occurrence of spotfires{\textemdash}new fires ignited by the transport of burning debris such as bark ahead of an existing fire. Under most burning conditions, spotfires play little role in the overall propagation of a fire, except where spread is impeded by breaks in fuel or topography and spotfires allow these impediments to be overcome. However, under conditions of severe bushfire behaviour spotfire occurrence can be so prevalent that spotting becomes the dominant propagation mechanism and the fire spreads as a cascade of spotfires forming a {\textquoteleft}pseudo{\textquoteright} front.

It has long been recognised that the presence of multiple individual fires affects the behaviour and spread of all fires present. The convergence of separate individual fires into larger fires is called coalescence and can lead to rapid increases in fire intensity and spread rate. This coalescence effect is frequently utilised in prescribed burning via multiple point ignitions to rapidly burn out large areas.

The zone between two coalescing fires is known as the convergence or junction zone and can be a very dangerous place to be for firefighters and may lead to highly erratic fire behaviour as witnessed during the 2003 Canberra fires. Fire behaviour under such conditions may be dominated by dynamic feedback processes between the energy released by each fire and the coupling of that energy with the atmosphere.

All existing operational fire behaviour models assume that a fire will burn at an approximately constant (quasi-steady) rate of spread for a given set of environmental conditions. While recent work showed that an individual fire starting from a point accelerates to this steady state, little research has been undertaken into the behaviour of multiple simultaneous adjacent ignitions under wildfire conditions or the effects of the dynamic feedbacks involved. No operational fire spread models currently account for the dynamical aspects of fire spread, particularly fire-fire interactions. This inability to accurately predict the behaviour of mass spotting events and the interactions of multiple adjacent fires places firefighters at risk and the general public in danger. With the projected climate change impacts expected to produce more extreme bushfires and prevalence of mass fire behaviour, this deficiency in our understanding and operational systems represents a considerable knowledge gap.

The effects of dynamic processes on fire spread cannot be calculated using tables, spreadsheets or simple calculators.\  To comprehensively account for the effects of dynamic fire spread it is necessary to model the phenomenon using a physics-based model that incorporates complete descriptions of the key processes, including interactions between the fire, the fuel, topography and the surrounding atmosphere. Unfortunately, such a modelling approach is computationally intensive, expensive and model run-times not conducive to operational application.

This project addresses these issues by investigating the processes involved in the coalescence of free-burning fires under experimentally controlled conditions, quantifying the physical mechanisms involved in these and investigating the geometric drivers of fire line propagation (e.g. fire line curvature) with the aim of developing a physically simplified proxy for some of the more complicated dynamical effects. This approach enables development of models that are able to effectively emulate the dynamics of fire spread without the need to explicitly model fire-atmosphere or fire-fire interactions in a computationally costly manner.\ 

}, issn = {129}, author = {Jason J. Sharples} } @conference {bnh-2096, title = {Linking local wildfire dynamics to pyroCB development - non peer reviewed extended abstract}, booktitle = {Adelaide Conference 2015}, year = {2015}, address = {Adelaide, Australia}, abstract = {

Research proceedings from the Bushfire and Natural Hazards CRC \& AFAC Conference in Adelaide, 1-3 September 2015.\ 

}, author = {Rick McRae and Jason J. Sharples and Michael Fromm and George Kablick} } @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} } @article {BF-3102, title = {Wind-terrain effects on the propagation of wildfires in rugged terrain: fire channelling}, journal = {International Journal of Wildland Fire}, year = {2011}, abstract = {The interaction of wind, terrain and a fire burning in a landscape can produce a variety of unusual yet significant effects on fire propagation. One such example, in which a fire exhibits rapid spread in a direction transverse to the synoptic winds as well as in the usual downwind direction, is considered in this paper. This type of fire spread, which is referred to as {\textquoteleft}fire channelling{\textquoteright}, is characterised by intense lateral and downwind spotting and production of extensive flaming zones. The dependence of fire channelling on wind and terrain is analysed using wind, terrain and multispectral fire data collected during the January 2003 Alpine fires over south-eastern Australia. As part of the analysis, a simple terrain-filter model is utilised to confirm a quantitative link between instances of fire channelling and parts of the terrain that are sufficiently steep and lee-facing. By appealing to the theory of wind{\textendash}terrain interaction and the available evidence, several processes that could produce the atypical fire spread are considered and some discounted. Based on the processes that could not be discounted, and a previous analysis of wind regimes in rugged terrain, a likely explanation for the fire channelling phenomenon is hypothesised. Implications of fire channelling for bushfire risk management are also discussed.}, doi = {10.1071/WF10055}, author = {Jason J. Sharples and Rick McRae and Wilkes, Stephen R.} } @article {BF-2418, title = {An overview of mountain meteorological effects relevant to fire behaviour and bushfire risk}, journal = {International Journal of Wildland Fire}, volume = {18}, year = {2009}, month = {2009}, pages = {737}, abstract = {Many of the processes that can occur in mountainous landscapes have the potential to significantly affect fire behaviour and bushfire risk in general. These processes can lead to otherwise unexpected fire behaviour and escalation in fire size and severity that could endanger firefighting crews and compromise suppression activities. Interaction of upper winds with rugged terrain can often result in highly variable and turbulent wind patterns and variations in temperature and humidity that can affect fire regimes in the long and short term. More generally, the effect of rugged terrain on atmospheric flows can give rise to complex dynamics and emergent properties that are discontinuous in nature. Hence, the {\textquoteleft}fire weather continuum{\textquoteright} that is often assumed in fire management practices is of reduced validity in mountainous or hilly landscapes. This paper presents an overview of the main elements of mountain meteorology relevant to fire weather and discusses the potential roles they may play in bushfire behaviour, development and risk. As such, the paper is intended to promote understanding, across the wide range of professions concerned with bushfire, of how mountain meteorological effects might contribute to fire potential and fire behaviour.}, doi = {10.1071/WF08041}, author = {Jason J. Sharples} } @article {BF-2419, title = {A simple index for assessing fire danger rating}, journal = {Environmental Modelling \& Software}, volume = {24}, year = {2009}, month = {06/2009}, pages = {764 - 774}, abstract = {Fire danger rating systems are used to assess the potential for bushfire occurrence, fire spread and difficulty of fire suppression. Typically, fire danger rating systems combine meteorological information with estimates of the moisture content of the fuel to produce a fire danger index. Fire danger indices are used to declare fire bans and to schedule prescribed burns, among other applications. In this paper a simple fire danger index F that is intuitive and easy to calculate is introduced and compared to a number of fire danger indices pertaining to different fuel types that are used in an operational setting in Australia and the United States. The comparisons suggest that F provides a plausible measure of fire danger rating and that it may be a useful pedagogical tool in the context of fire danger and fire weather.}, doi = {10.1016/j.envsoft.2008.11.004}, author = {Jason J. Sharples and Rick McRae and Weber, Rodney and Gill, A. Malcolm} } @article {BF-2390, title = {Review of formal methodologies for wind{\textendash}slope correction of wildfire rate of spread}, journal = {International Journal of Wildland Fire}, volume = {17}, year = {2008}, month = {2008}, pages = {179}, abstract = {The effects of wind and topographic slope are important considerations when determining the rate and direction of spread of wildfires. Accordingly, most models used to predict the direction and rate of spread contain components designed to account for these effects. Over the years, a variety of different approaches have been developed. In the present manuscript, we examine the various mathematical models employed to account for the effects of wind and slope at a formal level, making comparisons where appropriate. The methods reviewed include scalar methods, which ignore the directional nature of wind and slope effects, as well as methods in which the effects of wind and slope are combined in a vectorial manner. Both empirical and physical models for wind{\textendash}slope correction are considered.}, doi = {10.1071/WF06156}, author = {Jason J. Sharples} }