Advancing
the Science of Crown Fire Behavior
What you guys envisioned and so many of us worked on will
make fire history. Lots of excellent
work, data, concepts and techniques to stoke the research fires for a long time
to come. — Dr.
Ted Putnam[1] commenting
on the value of the International Crown Fire Modelling Experiment which took
place ~50 km northeast of Fort Providence, NWT.
The Canadian Journal of Forest
Research has recently published a special issue entitled “The International Crown Fire Modelling
Experiment (ICFME) in Canada's Northwest Territories: Advancing the Science of
Fire Behaviour”.
Dr. Marty Alexander, presently a Senior Researcher
with FERIC’s Wildland Fire Operations Research Group, served as one of the
organizers of ICFME while with the Canadian Forest (CFS) along with Brian
Stocks (CFS Great Lakes Forestry Centre, Sault Ste. Marie, Ontario) and Rick
Lanoville (Department of Resources, Wildlife and Economic Development, Forest
Management Division, Fort Smith, Northwest Territories). In addition, Brian Stocks served as the
special guest editor for the Canadian Journal of Forest Research.
The special issue features 10 articles. The first article represents an overview and
introduction to ICFME (Stocks, Alexander and Lanoville 2004). The other nine articles focus on some of the
main research studies carried out during the course of the ICFME which began in
1994 and concluded in 2001. This
includes papers dealing with different aspects of crown fire behavior (Butler,
Cohen, Latham et al. 2004; Butler, Finney, Andrews, Albini 2004; Stocks,
Alexander, Wotton et al. 2004; Taylor, Wotton, Alexander, Dalrymple 2004),
firefighter safety (Putnam and Butler 2004), the wildland-urban interface
(Cohen 2004), smoke chemistry (Payne, Stocks, Robinson et al. 2004), tree
regeneration (de Groot, Bothwell, Taylor et al. 2004), and charcoal deposits in
lake sediments (Lynch, Clark and Stocks 2004).
The abstracts for each of these articles are given below.
The cost for a single personal copy of the ICFME
special issue is $US35 for US residents and $CDN35 for Canadian residents. Requests must be prepaid (Visa and
Mastercard accepted). For more
information contact André Séguin, Subscription
Office, NRC Research Press, National Research Council Canada, Montreal Road,
Building M-55, Ottawa, Ontario K1A 0R6 (phone: 613-993-9084;
email:andre.seguin@nrc-cnrc.gc.ca).
The ICFME special issue of Canadian Journal of Forest
Research is Volume 34, Number 8, August 2004 (http://pubs.nrc-cnrc.gc.ca/cgi-bin/rp/rp2_tocs_e?cjfr_cjfr8-04_34).
CITATIONS and
ABSTRACTS
Stocks, B.J.; Alexander, M.E.; Lanoville, R.A. 2004.
Overview of the International Crown Fire Modelling Experiment (ICFME). Canadian
Journal of Forest Research 34: 1543-1547.
Abstract: The
International Crown Fire Modelling Experiment (ICFME), carried out between 1995
and 2001 in Canada's Northwest Territories, involved 18 experimental
high-intensity crown fires, with more than 100 participants representing 30
organizations from 14 countries. ICFME has provided valuable new data and
insights into the nature and characteristics of crowning forest fires, which
will assist in addressing fire management problems and opportunities affecting
both people and ecosystems in future decades. ICFME evolved as the result of a
number of converging issues: the recognition that the US and Canada could not
continue separate approaches to fire behaviour model development, the opening
of Russia to the western world, increased communication, and the formation of
international associations to facilitate collaboration. While the initial
impetus for ICFME was the desire to improve the physical modeling of crown fire
propagation and spread, the project also created the opportunity to examine
many other aspects and impacts of crown fires. This special issue of the Canadian
Journal of Forest Research devoted to ICFME is intended to summarize most
of the major research results from the project.
Stocks, B.J.; Alexander, M.E.; Wotton, B.M.; Stefner, C.N.; Flannigan, M.D.; Taylor, S.W.; Lavoie, N.; Mason, J.A.; Hartley, G.R.; Maffey, M.E.; Dalrymple, G.N.; Blake, T.W.; Cruz, M.G.; Lanoville, R.A. 2004. Crown fire behaviour in a northern jack pine – black spruce forest. Canadian Journal of Forest Research 34:1548-1560.
Abstract: This
paper reports on the behaviour of 10 experimental crown fires conducted between
1997 and 2000 during the International Crown Fire Modelling Experiment (ICFME)
in Canada's Northwest Territories. The primary goal of ICFME was a replicated
series of high-intensity crown fires designed to validate and improve existing
theoretical and empirical models of crown fire behaviour. Fire behaviour
characteristics were typical for fully developed boreal forest crown fires,
with fires advancing at 15–70 m/min, consuming significant quantities of fuel
(2.8–5.5 kg/m2) and releasing vast amounts of thermal heat energy.
The resulting flame fronts commonly extended 25–40 m above the ground with head
fire intensities up to 90 000 kW/m. Depth of burn ranged from 1.4–3.6 cm,
representing a 25%–65% reduction in the thickness of the forest floor layer.
Most of the smaller diameter (<3.0 cm) woody surface fuels were consumed,
along with a significant proportion of the larger downed woody material. A high
degree of fuel consumption occurred in the understory and overstory canopy with
very little material less than 1.0 cm in diameter remaining. The documentation
of fire behaviour, fire danger, and fire weather conditions carried out during
ICFME permitted the evaluation of several empirically based North American fire
behaviour prediction systems and models
Taylor,
S.W.; Wotton, B.M.; Alexander, M.E.; Dalrymple, G.N. 2004. Variation in wind and crown fire behaviour
in a northern jack pine – black spruce forest. Canadian Journal of Forest
Research 34: 1561-1576.
Abstract: Fire spread and flame temperature were examined in a series of nine experimental crown fires conducted in the Northwest Territories, Canada. Average rates of spread were 17.8–66.8 m·min–1 (0.3–1.1 m·s–1) over burning periods from about 1.5–10 min across 75 m × 75 m to 150 m × 150 m plots. Detailed maps of fire front progression revealed areas with higher rates of spread in the order of tens of metres in horizontal dimension and tens of seconds in duration in several of the fires, which is consistent with the influence of coherent wind gusts. Comparison of open and in-stand wind speed before and after burning suggests that defoliation in the canopy layer during burning would result in the flaming zone having greater exposure to the ambient wind. Estimates of flame front residence from video observations at the surface averaged 34 s; estimates from temperature measurements decreased significantly with height from 74 s at the surface to 31 s below the canopy.
Butler, B.W.;
Cohen, J.; Latham, D.J.; Schuette, R.D.; Sopko, P; Shannon, K.S.;
Jimenez, D.; Bradshaw, L.S. 2004.
Measurements of radiant emissive power and temperatures in crown fires.
Canadian Journal of Forest Research 34:1577-1587.
Abstract: This study
presents spatially and temporally resolved measurements of air temperatures and
radiant energy fluxes in a boreal forest crown fire. Measurements were
collected 3.1, 6.2, 9.2, 12.3, and 13.8 m above the ground surface. Peak air
temperatures exceeded 1330 °C, and maximum radiant energy fluxes occurred in
the upper third of the forest stand and reached 290 kW·m–2. Average
radiant flux from the flames across all experiments was found to be
approximately 200 kW·m–2. Measured temperatures showed some
variation with vertical height in the canopy. Equivalent radiometric
temperatures calculated from radiant heat flux measurements exceeded
thermocouple-based temperatures for all but the 10-m height, indicating that
fire intensity estimates based on thermocouple measurements alone may result in
underestimation of actual radiant intensity. The data indicate that the
radiative energy penetration distance is significantly longer in the forest
canopy than in the lower levels of the forest stand.
Butler, B.W.; Finney, M.A.; Andrews, P.L.; Albini, F.A.
2004. A radiation-driven model for
crown fire spread. Canadian Journal of Forest Research 34: 1588-1599.
Abstract: A numerical
model for the prediction of the spread rate and intensity of forest crown fires
has been developed. The model is the culmination of over 20 years of previously
reported fire modeling research and experiments; however, it is only recently
that it has been formulated in a closed form that permits a priori prediction
of crown fire spread rates. This study presents a brief review of the
development and structure of the model followed by a discussion of recent
modifications made to formulate a fully predictive model. The model is based on
the assumption that radiant energy transfer dominates energy exchange between
the fire and unignited fuel with provisions for convective cooling of the fuels
ahead of the fire front. Model predictions are compared against measured spread
rates of selected experimental fires conducted during the International Crown
Fire Modelling Experiment. Results of the comparison indicate that the closed
form of the model accurately predicts the relative response of fire spread rate
to fuel and environment variables but overpredicts the magnitude of fire spread
rates.
Putnam, T; Butler, B.W. 2004.
Evaluating fire shelter performance in experimental crown fires.
Canadian Journal of Forest Research 34: 1600-1615.
Abstract: Fire
shelters are critical safety items required for use by most wildland
firefighters in the United States. Most testing of fire shelters, clothing and
other personal protective equipment (PPE) has been limited to prescribed fires
or laboratory based studies. This study reports results from experiments where
lined and unlined stainless steel or aluminum and glass fabric shelters were
tested under high intensity crown fire conditions in and adjacent to
experimental burn plots. Firefighter clothing and standard (pre-2003) fire
shelters were also tested. Measured shelter surface and air temperatures and
thermal impact on firefighter personal protective equipment were used to deduce
the survivability of shelter designs and deployment location. Multiple glass
and aluminum layered shelters show more promise than stainless steel shelters
for improving overall fire shelter survivability. Data collected outside the
burn plots generally indicate decreased heating as distance from forest edge
increases, supporting the importance of maximizing distance from vegetation for
survivability. It is recommended that common experiment protocols be adopted so
that future research into fire shelter and PPE performance builds on
work-to-date and provides a common basis from which analyses can be completed.
Cohen, J.D. 2004. Relating flame radiation to home ignition
using modeling and experimental crown fires. Canadian Journal of Forest
Research 34: 1616-1626.
Abstract: Wildland–urban
fire destruction depends on homes igniting and thus requires an examination of
the ignition requirements. A physical–theoretical model, based on severe case
conditions and ideal heat transfer characteristics, estimated wood wall
ignition occurrence from flame radiation heating and piloted ignition
requirements. Crown fire experiments provided an opportunity for assessing
model reliability. The crown fire experiments were specifically instrumented
with wood wall sections and heat flux sensors to investigate direct flame
heating leading to home ignition during wildland fires. The experimental results
indicated that the flame radiation model overestimated the structure-to-flame
distance that would result in wood wall ignition. Wall sections that ignited
during the experimental crown fires did not sustain flaming after crown fire
burnout. The experiments also revealed that the forest canopy attenuated the
flame radiation as the crown fire spread within the forest plot. Ignition
modeling and the associated crown fire experiments described the
flame-to-structure distance scale associated with flame heating related to wall
ignition.
Payne, N.J.; Stocks, B.J.; Robinson, A.; Wasey, M.; Strapp, J.W.
2004. Combustion aerosol from
experimental crown fires in a boreal forest jack pine stand. Canadian Journal
of Forest Research 34: 1627-1633.
Abstract: Combustion
aerosol particles from boreal forest fires were quantified to facilitate
investigation of the potential effects of increased fire activity caused by
global warming, by providing data inputs for global and regional climate
modelling of the direct and indirect effects. Aerial sampling was carried out
in smoke plumes from 1-ha prescribed burns in mature jack pine stands. The
three sampled burns resulted in crown fires, with fuel consumption from 4.2 to
5.8 kg·m–2. Accumulation and coarse mode aerosol (>0.1 µm) was
quantified using a passive cavity aerosol spectrometer probe and cascade
impactor. The number median diameter of particles in the smoke plume was 0.29
µm, and the peak number and cross-sectional area density occurred around a
particle size of 0.4 µm. More than 99% of particles sized had diameters <1.2
µm. Aerosol from flaming combustion was coarser than that from the smouldering
phase, with number median diameters of 0.3 and 0.2 µm, respectively.
de Groot, W.J.; Bothwell, P.M.; Taylor, S.W.; Wotton,
B.M.; Stocks, B.J.; Alexander, M.E. 2004. Jack pine regeneration and crown
fires. Canadian Journal of Forest Research 34: 1634-1641.
Abstract: The effect of
crown fires on Pinus banksiana Lamb. regeneration was studied in
separate forest- and cone-burning experiments. Nine plots (0.56–2.25 ha) of
jack pine trees near Fort Providence, Northwest Territories, were burned using
crown fires to determine the effects of fire intensity, rate of fire spread,
depth of burn, and postfire duff depth on seed viability and regeneration. Fire
intensities were 36 902 – 93 476 kW/m, and fire spread rates were
24–70 m/min. Depths of burn were low (2.0–3.6 cm), and postfire duff depths
averaged 2.0–5.5 cm. Postfire seed rain was highly variable (64–634 seeds/m2),
but seed viability was near 67% on all plots. Jack pine regeneration was also
highly variable (7–79 seedlings/m2). In the cone-burning experiment,
the germination rate increased from 41% (unheated cones) to 64% after 10 s of
burning but decreased sharply after 30 s. Flame temperature did not
significantly affect viability. Cone-burning results suggest that the postfire
seed rain originated from the upper canopy, where flame duration was 5–15 s,
and seed in the lower canopy was consumed by fire. Seed rain and regeneration
were primarily influenced by understory fine fuel consumption (and therefore,
fire intensity), tree height, and live crown base height
Lynch, J.A.; Clark, J.S.; Stocks, B.J. 2004. Charcoal production, dispersal, and
deposition from the Fort Providence experimental fire: interpreting fire
regimes from charcoal records in boreal forests. Canadian Journal of Forest
Research 34: 1642-1656.
Abstract: The
relationship between charcoal production from fires and charcoal deposition in
lakes is poorly understood, which limits the interpretation of sediment
charcoal records. This calibration study assessed charcoal particle production,
size, and transport during the International Crown Fire Modelling Experiment
(ICFME) and compared fossil charcoal particle accumulation from 16 lakes in
boreal forests of North America. Particle accumulation averaged 20.1 mm2·cm–2
inside the ICFME fire; accumulation declined sharply outside the fire, with
only 1% of the measured particles transported beyond 20 m from the burn edge.
Fossil charcoal accumulation during the past 9000 years was much lower than
observed deposition in traps located within the ICFME fire but similar to
airborne deposition in traps located 10–60 m from the burn edge. A higher
fraction of large diameter particles (>1 mm) was present in fossil charcoal
accumulation from historical fires and charcoal peaks that exceeded background
accumulation by 1.4 times, suggesting large particles are characteristic of
nearby fires. On the basis of a charred-particle production of ~2% of the total
fuel consumed by the ICFME fire, we estimate a potential long-term carbon
sequestration of 58.2 ± 12 g C·m–2 as charred particles from this
fire stored in soils or lake sediments.