Fire Growth and Acceleration

1997 ◽  
Vol 7 (1) ◽  
pp. 1 ◽  
Author(s):  
NP Cheney ◽  
JS Gould
Keyword(s):  
Equilibrium State ◽  
Weather Conditions ◽  
Fire Growth ◽  
Fire Size ◽  
Acceleration Phase ◽  
Characteristic Curves ◽  
Rate Of Spread ◽  
Steady Rate ◽  
In Fire ◽  
Practical Implications

The use of the terms "growth" and "acceleration" appears to be inconsistent in the literature and we believe this inconsistency has hindered our understanding of behaviour in the early stages of a fire. The development of a fire from a point ignition to some equilibrium state and the associated increase in fire size and intensity has been referred to variously as the fire growth (Pyne 1984); build-up (Luke and McArthur 1978); or acceleration (Chandler et al. 1983) phase of the fire. More specifically the "acceleration phase" has been used to describe the increase in rate of spread from ignition to a quasi-steady rate of spread (Luke and McArthur 1978, McAlpine and Wakimoto 1991). Characteristic curves showing the increase in rate of spread are illustrated for different fuel and weather conditions (Luke and McArthur 1978). Hypothetical models to describe these curves have been proposed by Cheney and Bary (1969), Van Wagner (unpublished) and McAlpine and Wakimoto (1991). They have been called acceleration curves and acceleration models. The terms growth and acceleration, however, represent different concepts that are not interchangeable. We would like to clarify these concepts and discuss the practical implications for fire managers.

Modelling the effects of landscape fuel treatments on fire growth and behaviour in a Mediterranean landscape (eastern Spain)

2007 ◽  
Vol 16 (5) ◽  
pp. 619 ◽  
Author(s):  
Beatriz Duguy ◽  
José Antonio Alloza ◽  
Achim Röder ◽  
Ramón Vallejo ◽  
Francisco Pastor
Keyword(s):  
Spatial Distribution ◽  
Fire Spread ◽  
Fire Growth ◽  
Fire Size ◽  
Fire Propagation ◽  
Area Burned ◽  
Rate Of Spread ◽  
Mediterranean Countries ◽  
Fuel Accumulation ◽  
Fire Characteristics

The number of large fires increased in the 1970s in the Valencia region (eastern Spain), as in most northern Mediterranean countries, owing to the fuel accumulation that affected large areas as a consequence of an intensive land abandonment. The Ayora site (Valencia province) was affected by a large fire in July 1979. We parameterised the fire growth model FARSITE for the 1979 fire conditions using remote sensing-derived fuel cartography. We simulated different fuel scenarios to study the interactions between fuel spatial distribution and fire characteristics (area burned, rate of spread and fireline intensity). We then tested the effectiveness of several firebreak networks on fire spread control. Simulations showed that fire propagation and behaviour were greatly influenced by fuel spatial distribution. The fragmentation of large dense shrubland areas through the introduction of wooded patches strongly reduced fire size, generally slowing fire and limiting fireline intensity. Both the introduction of forest corridors connecting woodlands and the promotion of complex shapes for wooded patches decreased the area burned. Firebreak networks were always very effective in reducing fire size and their effect was enhanced in appropriate fuel-altered scenarios. Most firebreak alternatives, however, did not reduce either rate of fire spread or fireline intensity.

scholarly journals Regional seasonality of fire size and fire weather conditions across Australia's northern savanna

2020 ◽  
Vol 29 (1) ◽  
pp. 1 ◽  
Author(s):  
Justin J. Perry ◽  
Garry D. Cook ◽  
Erin Graham ◽  
C. P. (Mick) Meyer ◽  
Helen T. Murphy ◽  
...  
Keyword(s):  
Prescribed Burning ◽  
Fire Regime ◽  
Weather Conditions ◽  
Temporal Variations ◽  
Dry Season ◽  
Fire Weather ◽  
Fire Size ◽  
Spatial Consistency ◽  
In Fire ◽  
Extreme Fire

Australia’s northern savannas have among the highest fire frequencies in the world. The climate is monsoonal, with a long, dry season of up to 9 months, during which most fires occur. The Australian Government’s Emissions Reduction Fund allows land managers to generate carbon credits by abating the direct emissions of CO2 equivalent gases via prescribed burning that shifts the fire regime from predominantly large, high-intensity late dry season fires to a more benign, early dry season fire regime. However, the Australian savannas are vast and there is significant variation in weather conditions and seasonality, which is likely to result in spatial and temporal variations in the commencement and length of late dry season conditions. Here, we assess the temporal and spatial consistency of the commencement of late dry season conditions, defined as those months that maximise fire size and where the most extreme fire weather conditions exist. The results demonstrate that significant yearly, seasonal and spatial variations in fire size and fire weather conditions exist, both within and between bioregions. The effective start of late dry season conditions, as defined by those months that maximise fire size and where the most extreme fire weather variables exist, is variable across the savannas.

Modelling the dynamic behaviour of junction fires with a coupled atmosphere–fire model

2017 ◽  
Vol 26 (4) ◽  
pp. 331 ◽  
Author(s):  
C. M. Thomas ◽  
J. J. Sharples ◽  
J. P. Evans
Keyword(s):  
Fire Spread ◽  
Community Safety ◽  
Fire Behaviour ◽  
Ambient Conditions ◽  
Fire Model ◽  
Fire Propagation ◽  
Dynamic Propagation ◽  
Rate Of Spread ◽  
Steady Rate ◽  
In Fire

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–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.

scholarly journals Establishing Propagation Nodes as a Basis for Preventing Large Wildfires: The Proposed Methodology

2020 ◽  
Vol 3 ◽  
Author(s):  
Raúl Quílez ◽  
Luz Valbuena ◽  
Jordi Vendrell ◽  
Kathleen Uytewaal ◽  
Joaquín Ramirez
Keyword(s):  
Climate Change ◽  
Management Practices ◽  
New Technologies ◽  
Management Strategies ◽  
Fire Behavior ◽  
Weather Conditions ◽  
Rate Of Spread ◽  
Socioeconomic Changes ◽  
Forest Fire Management ◽  
In Fire

In Spain, traditional forest fire management practices have been conducted for many decades, for both prevention- and extinction-oriented purposes. This management model has been forced to shift as a result of changes in fire behavior and has also been adapted to the use of new technologies. The challenge presented by wildfires is amplified due to socioeconomic changes in the last 40 years and inadequate land management in the context of climate change. The principal objective of this work is to establish the most adequate methodology to define the “propagation nodes” in a territory. To do that, the new simulation modes offered by the WildFire AnalystTM simulator (WFA) have been explored to obtain fire behavior data. Likewise, the behavior of large fires in the area has been extrapolated to future scenarios, according to forecasts of different climate change, analyzing extreme weather conditions that can occur in such scenarios (ONU, 2019). The WFA simulator (Tecnosylva, 2014) works efficiently in simulating fire, proving greatly useful in both real suppression operations and fire prevention analysis. It can very accurately generate large wildfires' main pathways without making any kind of adjustments; this is quite useful when planning operations at the head of a fire. It also allows evacuation time evaluation for a given Wildland Urban Interface zone. The area selected for this study is called Sot de Chera, in the Valencia region (Spain). The methodology employed here uses the simulation with WFA setting extreme meteorological and phenological windows associated with wind-driven fires or convection fires dominated with wind, from different starting points looking for the areas where they are grouped. In other words, it is a matter of identifying on the territory the areas where the heads of these higher-intensity fires will arrive, in order to offer realistic control possibilities to the firefighting teams. The results of the simulation identify the heads of the fires with the greatest rate of spread and intensity, exceeding suppression capabilities and efforts, allowing thus to plan for appropriate fuel management strategies to effectively manage emergency responses to fires in these areas.

Relative importance of weather and climate on wildfire growth in interior Alaska

2011 ◽  
Vol 20 (4) ◽  
pp. 479 ◽  
Author(s):  
John T. Abatzoglou ◽  
Crystal A. Kolden
Keyword(s):  
Meteorological Data ◽  
Weather Data ◽  
Fire Growth ◽  
Fire Size ◽  
Daily Weather Data ◽  
Weather And Climate ◽  
Dry Conditions ◽  
Large Fires ◽  
In Fire

Efforts to quantify relationships between climate and wildfire in Alaska have not yet explored the role of higher-frequency meteorological conditions on individual wildfire ignition and growth. To address this gap, meteorological data for 665 large fires that burned across the Alaskan interior between 1980 and 2007 were assessed to determine the respective influence of higher-frequency weather and lower-frequency climate, in terms of both antecedent and post-ignition conditions on fire growth. Antecedent climate exhibited no discernable influence on eventual fire size. In contrast, fire size was sensitive to weather in the days to weeks following ignition, particularly the post-ignition timing of precipitation. Prolonged periods of warm and dry conditions coincident with blocking that persists for several weeks after ignition enabled growth of large wildfires, whereas the return of wetting precipitation generally within a week after ignition inhibited growth of smaller wildfires. These results suggest that daily weather data are a critical predictor of fire growth and large fire potential and encourage their use in fire management and modelling.

Fire Growth in Grassland Fuels

1995 ◽  
Vol 5 (4) ◽  
pp. 237 ◽  
Author(s):  
NP Cheney ◽  
JS Gould
Keyword(s):  
Wind Speed ◽  
Fire Spread ◽  
Small Scale ◽  
Fire Growth ◽  
Spread Rate ◽  
Wind Speeds ◽  
Rate Of Spread ◽  
Steady Rate ◽  
Scale Field ◽  
Wildfire Spread

The development of grass fires originating from both point and line ignitions and burning in both open grasslands and woodlands with a grassy understorey was studied using 487 periods of fire spread and associated fuel, weather and fire-shape observations. The largest fires travelled more than 1000 m from the origin and the fastest 2-minute spread rate was over 2 m s-1. Given continuous fuel of uniform moisture content, the rate of forward spread was related to both the wind speed and the width of the head fire measured normal to the direction of fire travel. The head fire width required to achieve the potential quasi-steady rate of forward spread for the prevailing conditions increased with increasing wind speeds. These findings have important implications for relating small-scale field or laboratory measurements of fire spread to predictions of wildfire spread. The time taken to reach the potential quasi-steady rate of spread at any wind speed was highly variable. This time was strongly influenced by the frequency of changes in wind direction and the rate of development of a wide head fire.

Width of firebreak that is necessary to stop grass fires: some field experiments

1988 ◽  
Vol 18 (6) ◽  
pp. 682-687 ◽  
Author(s):  
Andrew A. G. Wilson
Keyword(s):  
Response Function ◽  
Field Experiments ◽  
Flame Length ◽  
Northern Territory ◽  
Forward Rate ◽  
Rate Of Spread ◽  
Practical Implications

Firebreaks were tested in the Northern Territory of Australia for their performance in halting the spread of 113 experimental grass fires burning in blocks which ranged from 1 to 4 ha in size. The widths of firebreak tested ranged from 1.5 to 15 m. The most intense of the fires burnt with a rate of spread of 1.9 m s−1 and had a fireline intensity of 17 MW m−1. The fastest fire stopped by a firebreak burnt with a forward rate of spread of 2.2 m s−1 and had a fireline intensity of 8 MW m−1. A logistic response function was fitted to the data on firebreak breach; this resulted in an equation for predicting the probability of firebreak breach. The probability of firebreak breach was found to increase with increasing fireline intensity and the presence of trees within 20 m of the firebreak and to decrease with increasing firebreak width. A published relationship between fireline intensity and flame length provided a sensible approximation to the width of firebreak that could be breached, via flame contact, by a fire of a given fireline intensity. Practical implications of the results are discussed.

Calculation of fire spread rates across random landscapes

2003 ◽  
Vol 12 (2) ◽  
pp. 167 ◽  
Author(s):  
Mark A. Finney
Keyword(s):  
Travel Time ◽  
Growth Rates ◽  
Fire Spread ◽  
Harmonic Mean ◽  
Fire Growth ◽  
Fire Size ◽  
Spread Rate ◽  
Fuel Treatments ◽  
Fuel Mixtures

An approach is presented for approximating the expected spread rate of fires that burn across 2-dimensional landscapes with random fuel patterns. The method calculates a harmonic mean spread rate across a small 2-dimensional grid that allows the fire to move forward and laterally. Within this sample grid, all possible spatial fuel arrangements are enumerated and the spread rate of an elliptical fire moving through the cells is found by searching for the minimum travel time. More columns in the sample grid are required for accurately calculating expected spread rates where very slow-burning fuels are present, because the fire must be allowed to move farther laterally around slow patches. This calculation can be used to estimate fire spread rates across spatial fuel mixtures provided that the fire shape was determined from wind and slope. Results suggest that fire spread rates on random landscapes should increase with fire size and that random locations of fuel treatments would be inefficient in changing overall fire growth rates.

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