wildfires in Colorado, Oregon, Arizona, and California this summer
were searing reminders that uncontrolled fires in forests and brushlands
pose an increasing threat to life, property, and natural resources.
After 100 years of fire suppression activities, combined with unusually
hot and dry weather patterns, dangerous amounts of highly flammable
fuels have accumulated throughout the nation.
result, millions of acres of forests and brushlands and thousands
of homes are at high risk. The problem is exacerbated as people
continue to relocate from urban to rural areas and homes and communities
are built adjacent to state and national forests.
nations capability to respond to wildfires is becoming overextended,
says Livermore atmospheric scientist Michael Bradley. It is
essential that we do all we can to ensure firefighters safety
and increase their ability to efficiently limit the spread of potentially
notes that fire managers have an arsenal of weapons at their disposal,
ranging from aerial tankers to small armies of dedicated firefighters.
One weapon that is lacking, however, is a physics-based computer
simulation system that can accurately predict wildfire behavior
for specific weather conditions, types of vegetation, and terrain.
Such a capability would help fire managers to plan for different
fire scenarios, anticipate where and how quickly a fire will spread,
and evaluate the effectiveness of alternative firefighting strategies.
With this modeling capability, fire managers could use their limited
personnel and equipment much more effectively, thereby saving lives,
property, and irreplaceable natural resources.
a simulation capability is being developed for the first time by
a team of researchers from Lawrence Livermore and Los Alamos national
laboratories. Supported by Laboratory Directed Research and Development
funds, the project combines a physics-based wildfire model developed
at Los Alamos with the extensive emergency response capabilities
of the National Atmospheric Release Advisory Center (NARAC) at Livermore,
including its weather prediction and smoke transport codes and Livermores
supercomputers. The effort combines the special capabilities and
resources of the two laboratories, says Bradley, who leads the Livermore
effort that also includes atmospheric scientists Charles Molenkamp
and Martin Leach and geographical information systems (GIS) experts
Charles Hall, Lee Neher, and Lynn Wilder.
wildfire behavior is not a new concept. The models most widely used
by firefighters, however, are relatively unsophisticated programs
based on data obtained by laboratory experiments, for example, the
burn rate of pine needles in wind tunnels. Such experimental results
for a variety of vegetative fuels are used in look-up tables to
estimate burn rates based on the total amount of fuel, wind speed,
and the slope of simplified two-dimensional terrain. The model is
then used to predict wildfire behavior, guide firefighting tactics,
and assist in training and planning.
models do not account for the many complex physical processes that
characterize real wildfires and determine their behavior,
says Bradley. The models also dont reflect how the terrain
and vegetation change (sometimes dramatically within a few meters),
how the weather changes, and, perhaps most importantly, how the
fire and weather continuously interact.
air temperature, humidity, and precipitation, for example, influence
the flammability of fuel and largely determine the risk of fire
ignition. In addition, wind speed and direction determine the rate
of fire spread and the amount of transported embers from which new
fires can be ignited. Weather conditions also determine the location
and concentration of smoke plumes, which can interfere with ground
and aerial firefighting operations and cause health hazards downwind.
the heat from wildfires causes rising air currents that strongly
modify local weather patterns and create rapidly changing winds
that may fan the fire. As a fire approaches, unburned vegetation
preheats and dries and ignites more easily. All of these interacting
physical processes are reflected by the LivermoreLos Alamos
||Existing wildfire models,
using data from isolated laboratory experiments, do not adequately
represent the complicated, interactive processes of wildfires
defined in this diagram.
Model Starts with FIRETEC
The basic fire-simulation code, called FIRETEC,
has been developed over the past 7 years by a Los Alamos group headed
by atmospheric scientist Rod Linn. The group experienced first-hand
the destructive power of wildfires in 2000, when the Cerro Grande
fire ripped through the Santa Fe national forest as well as parts
of the town of Los Alamos and the Laboratory itself.
FIRETEC simulates the mechanisms
of fire propagation in ways that far exceed the capabilities of
wildfire models currently in use. FIRETEC predicts the spread of
wildfires based on a fundamental treatment of physical processes
such as combustion and turbulence and uses a terrain-following coordinate
system based on digitized maps. It takes into account the two basic
heating mechanisms of fire: the turbulent convective motion of heated
air and the infrared radiation emitted by the fire. Using spatial
resolutions of 1 to 10 meters, FIRETEC also tracks the depletion
of fuels and oxygen during combustion.
The code realistically represents
the vegetation of an area, including the mixture of species, their
densities, and their three-dimensional structure. Because the code
includes a vertical fuel representation, it differentiates between
grass, tree trunks, and tree crowns, thereby making simulations
much more realistic. This degree of realism is needed because in
some situations grass will burn without the fire spreading to tree
crowns, whereas in other situations, the crowns ignite. In simple
models, says Bradley, fuel is simply flat, represented
by a calculated number of tons of vegetation per acre, with no vertical
To account for the interactions
between fire and atmosphere, the Los Alamos group combined FIRETEC
with the fine-resolution, high-gradient flow solver program known
as HIGRAD, which was developed by Jon Reisner. HIGRAD delivers accurate
atmospheric simulations at extremely high spatial (1 meter) and
temporal (thousandths of a second) resolution.
HIGRAD, however, cannot
represent the regional weather patterns within which wildfires burn.
HIGRAD simulates close-in air flow over small regions of a
fire but does not take into account more remote weather processes
such as cold fronts, high- and low- pressure systems, and precipitation
that develop over much larger geographical areas, says Bradley.
|The Claremont Resort narrowly
escaped destruction during the 1991 wildfire in the hills of
Oakland and Berkeley, California.
To overcome this limitation,
the team incorporated the Coupled OceanAtmosphere Mesoscale
Prediction System (COAMPS), developed by the U.S. Naval Research
Laboratory in Monterey, California, and later refined by NARAC scientists.
COAMPS is run twice daily by NARAC to predict regional weather at
scales ranging from about 1,000 kilometers down to a few kilometers.
The Livermore wildfire team has run COAMPS using horizontal resolutions
as fine as approximately 150 meters. COAMPS predicts winds, temperature,
pressure, humidity, and precipitation for several days. The code
is formulated in terrain-following coordinates, which are advantageous
for atmospheric simulations over rugged terrain. COAMPS provides
the regional atmospheric environment within which HIGRADFIRETEC
simulations run, explains Bradley.
He says that integrating
HIGRADFIRETEC with NARACs capabilities provides access
to a wide range of resources that strengthen the wildfire simulation
capability. These resources include a detailed global terrain database,
global mapping system, global weather data acquisition system, and
weather prediction systems. NARAC is supported by vast quantities
of meteorological data that are collected dailyand sometimes
hourlyfrom around the world.
NARAC also has the leading
atmospheric smoke dispersion simulation model, called ARAC-3. Although
the model was originally conceived to track radionuclide releases,
the center can use it to respond to atmospheric releases of other
materials, including toxic chemicals, biological agents, ash from
volcanic eruptions, and, most relevantly for firefighting, smoke.
Following Operation Desert Storm, NARAC provided twice-daily predictions
of smoke dispersion from the burning oil wells in Kuwait. More recently,
it predicted the dispersion of smoke from two massive tire-dump
fires near Tracy and Wesley, California, from which smoke rose to
almost 2,000 meters above ground level. (See S&TR, June
of Coming Hazards.)
Livermore also offers substantial
supercomputer resources. Computer models that accurately predict
the behavior of wildfires require enormous processing power that
currently can only be provided by massively parallel supercomputers
(machines using many processors in tandem). Wildfire simulations
performed at Livermore, for example, typically use 64, 64-bit processors
belonging to Livermores TeraCluster2000 680-billion-operations-per-second
|(a) East Bay Regional Parks
ranger Bill Nichols (left) and Livermore researchers Charles
Molenkamp (center) and Michael Bradley used global positioning
system tools to determine for the first time the ignition points
of the 1991 fire in the OaklandBerkeley hills. (b) The
ignition point for the second fire (which began Sunday, October
20, 1991) in Tunnel Canyon is circled.
Threats and Responses
the simulation programs development, the LivermoreLos
Alamos team has conferred with federal, state, and local fire managers.
Many valuable suggestions have been incorporated into the programs
capabilities, and several applications have emerged.
preparedness planning and long-term planning for communities and
wildland managementare available now. With adequate funding,
three additional applicationsanalyzing specific fire threats,
predicting fire behavior for prescribed burns, and training firefighterscould
be ready next summer. The ultimate goal, real-time firefighting
support, is several years away and awaits the development of even
more powerful computers for faster turnaround.
The wildfire preparedness
planning application permits realistic simulations of past or hypothetical
future fires for specific locations, with high-resolution modeling
of terrain, types of vegetation, and weather conditions. This
is a powerful tool for community fire preparedness planning,
The long-term planning application
permits evaluation of vegetation management options such as thinning
trees or designing fuel breaks. Such planning is especially important
at the urbanwildland interface in determining the fire threat
to new homes, commercial development, and open areas.
Fire behavior predictions
for prescribed burns would be available to fire managers a few hours
before they ignite the fuel. This advance knowledge would enable
managers to decrease the risk of prescribed burns going out of control
(such as happened with New Mexicos Cerro Grande wildfire)
and of violating air quality standards.
Fire threat analyses would
produce physics-based predictions of potential fire behavior for
specific locations with a few days notice. This feature would
be particularly useful to fire managers in assessing the relative
risks of fire breaking out at various locations during periods of
As a training tool, the program
would be unsurpassed at showing how different factors affect the
behavior of wildfires. After specifying the exact ignition point
of a fire, students could vary the weather, vegetation, fuel conditions,
and firefighting methods to understand their effects. We envision
this application serving a role similar to that of a flight simulation
program, says Bradley. Students could make mistakes
without risking their lives.
The programs ultimate
goal is real-time support for firefighters. In this application,
the program would help fire managers to make critical operating
decisions regarding the deployment of firefighters and equipment.
The program could also predict the relative effectiveness of various
firefighting procedures, such as fuel breaks, backfires, air tanker
fire-retardant drops, and helicopter water drops.
|The wildfire modeling capability
zooms down to extremely fine resolution. For the OaklandBerkeley
hills fire that began October 20, 1991, the team constructed
(a) a virtual atmosphere by using historical weather data provided
by the European Center for Medium Range Weather Forecasting.
The data, which had a resolution of about 120 kilometers, were
fed into the Coupled OceanAtmosphere Mesoscale Prediction
System (COAMPS) to simulate (b) the humidity, temperature, wind
direction, and wind speed over the San Francisco Bay Area. The
COAMPS data were used by the high-gradient flow solver (HIGRD)
program to simulate (c) fine-scale weather at 10-meter resolution
over the OaklandBerkeley hills.
team has been validating the program by simulating well-documented
wildfires. An early simulation using HIGRADFIRETEC successfully
re-created the Corral Canyon wildfire that occurred in Calabasas,
near Malibu, California, on October 22, 1996. The fire had been
smoldering in the riparian (vegetation along a gully) area at the
bottom of a canyon. It suddenly rushed up one side of the canyon,
catching firefighters off guard and injuring several. The simulation
re-creates the rapid spread of the fire, from the bottom of the
drainage area to the crest of the hill, within 28 minutes, about
the time the actual fire took. By comparison, a simulation of the
same fire with a traditional model predicts that it would take about
6 hours to burn the same area. The difference between the two simulations
is the interplay among the terrain, fire, and winds that is represented
sometimes think they have a lot of time when they really dont,
says Bradley. The Corral Canyon simulation showed that strong sea
breezes channeled by the terrain pushed the fire up the hill much
faster than the firefighters thought possible. The model also shows
that if the riparian vegetation were replaced with dry grass, the
fire spreads up both sides of the canyon. The simulation results
are encouraging because they compare so well with field observations,
To provide a more exhaustive
validation of the programs capabilities, Bradley and his group,
together with Livermore GIS experts, have been reconstructing the
early stages of the catastrophic 1991 fire in the hills of Oakland
and Berkeley, California, and are looking at current fire dangers
to neighborhoods that escaped the conflagration. Bradley is sharing
the results with East Bay fire agencies, the city governments of
Oakland, Berkeley, and El Cerrito, the East Bay Regional Park District,
the East Bay Municipal Utilities District, the University of California
at Berkeley, Lawrence Berkeley National Laboratory, and the California
Department of Forestry and Fire Protection.
hills fire claimed 25 lives and destroyed more than 3,000 dwellings.
The simulations re-create its start at about 11 a.m. on Sunday,
October 20, 1991, in Tunnel Canyon. (One day earlier, a small grass
fire occurred about 100 meters from the ignition point of Sundays
fire. Embers from Saturdays fire, at first thought to have
been extinguished, almost certainly started the Sunday conflagration.)
Working with the East Bay
Regional Park District, the Livermore group produced the first global
positioning satellite coordinates for the ignition points of the
Saturday and Sunday fires. Next, the team built a virtual atmosphere
for October 20, 1991, by using historical weather data provided
by the European Center for Medium Range Weather Forecasting. The
data, which had a resolution of about 120 kilometers, were fed into
COAMPS to simulate the humidity, temperature, wind direction, and
wind speed over the area of the incipient wildfire.
||A topographical map of part
of the greater San Francisco Bay Area. The Coupled OceanAtmosphere
Mesoscale Prediction System (COAMPS) weather prediction code
modeled the larger area, while the high-gradient flow solver
code (HIGRAD) is restricted to a 1.6-square-kilometer area directly
over the OaklandBerkeley hills fire.
Front Yard Weather
The COAMPS data were used
by HIGRAD to simulate fine-scale weather at 10-meter resolution.
At this resolution, were actually simulating the weather
that occurred in the front and back yards of individual homes in
the OaklandBerkeley hills, notes Bradley. Volumes of
detail on the terrain and vegetation were fed into FIRETEC along
with the dimensions of a football-shaped scar on the hillside, which
resulted from the Saturday fire.
The fire was lit
in the FIRETEC program by raising the temperature by 100°C at
the exact ignition location determined earlier by the Livermore
team. The simulation shows wind-whipped flames quickly spreading
outward from the ignition point throughout Tunnel Canyon, which
contained bone-dry trees, bushes, and grasses. Other aspects of
the simulation show the direction and speed of winds (as affected
by the fire) and the percentage of vegetation burned.
Bradley says that a common
reaction to watching the simulations is that the fire spreads unrealistically
fast, but fire officials who have seen the simulation say it is
an accurate representation of what happened. Conditions were
nearly perfect for a devastating fire, Bradley says.
As with the Calabasas fire
simulation, the Oakland hills model shows that the exact ignition
location is important. If Sundays ignition point is moved
only 100 meters away, to the other side of the canyon, the fire
follows a different course.
team has also developed a fire consequence analysis capability by
meshing model results with data maps created with computerized GIS
tools. (See S&TR, September
New World of Maps.) GIS analyses make the program more useful
to fire chiefs and other emergency planners by superimposing layers
of digitized visual information over the simulation. The GIS map
layers include roads, schools, fire stations, electrical transmission
lines, and even the location of fire hydrants. A GIS layer of land
parcel maps, for example, allows users to select specific homes
and determine their vulnerability to wildfires.
By combining the wildfire
models with GIS tools, says Bradley, fire chiefs and analysts can
plan the best routes for firefighters to take as well as the safest
evacuation routes for residents at risk. Planners can also readily
determine the effects of thinning stands of trees or building fire
The Livermore group is particularly
interested in areas in the Oakland and Berkeley hills that didnt
burn in 1991 and that contain a substantial amount of vegetation,
homes, and research facilities. The group hopes to evaluate the
effectiveness of fuel breaks and other vegetation management techniques
for areas that escaped the 1991 fire. It also hopes to simulate
wildfires in Claremont Canyon and in Strawberry Canyon, the site
of Lawrence Berkeley National Laboratory, the Lawrence Hall of Science,
and a portion of the University of California at Berkeley campus.
These simulations will not only help the group to further understand
and improve the model, but they will also provide valuable information
for local agencies.
Bradley notes that the Oakland
and Berkeley hills areas are telling examples of the dangers posed
by the urbanwildland interface, where homes are nestled within
||A sequence of three frames
taken from the computer simulation of the OaklandBerkeley
hills fire, which started in Tunnel Canyon. (a) A football-shaped
dark area corresponding to Saturdays extinguished fire
can be seen. Sundays fire broke out just 30 meters away.
(b) Three-hundred seconds (5 minutes) later, the fire is spreading
quickly up the canyon. (c) Six-hundred seconds (10 minutes)
after ignition, the fire has spread to neighboring canyons.
to Make History
Because prescribed burns
are planned far in advance, they provide the best opportunity for
validating the programs accuracy. The burn location and ignition
time are known before the burn occurs; the amount, type, and moisture
content of vegetation are calculated before ignition; the weather
conditions are known; and the behavior of the fire can be documented.
Bradley has successfully
simulated smoke dispersion from several prescribed burns that were
conducted at Site 300, Livermores remote research facility.
The simulations used the ARAC-3 dispersion model and compared well
with observations of the smoke plume. He is hoping to use the full
predictive power of the LivermoreLos Alamos model to provide
reliable estimates of the fire behavior and smoke dispersion at
least 24 hours before the prescribed burns are ignited at Site 300
By next summer, it
is possible we will be able to run the system fast enough to predict
the first 30 minutes or so of the fires behavior during a
prescribed burn. If we are successful, it will be a truly historic
event for fire science. The team also has received several
offers from fire management agencies to participate in their prescribed
|(a) A simulation of the wind
with 10-meter resolution immediately before ignition of the
OaklandBerkeley hills fire. The arrows directions
indicate wind direction, while the arrows lengths indicate
wind speed. The red box is the fires ignition site. (b)
One and one-half minutes after ignition, winds are significantly
altered by the fast-moving fire (perimeter is outlined).
|These images combine the result
of (a) a computer simulation of an early stage of the OaklandBerkeley
hills fire with (b) a geographical information systems map of
land parcels in the OaklandBerkeley hills. Any home on
the land parcel map can be selected to determine its address
and its risk from a fire.
The concept of an advanced
wildfire simulation capability has been received positively by potential
users. As the programs development has progressed, an increasing
number of agencies have expressed interest in the project, including
the Los Angeles County Fire Department, the nations largest.
In October, the University of California sponsored a wildfire physics
workshop that explored how other scientists and fire managers can
use the LivermoreLos Alamos program as the basis for advanced
wildfire behavior studies. We want to build a community of
scientists and firefighters, says Bradley. A second workshop
is planned for early next year.
The team is looking at the
current program as a central core to which additional modules can
be added to strengthen its overall capabilities. For example, the
increasing threat of wildfire at the wildlandurban interface
makes it appropriate to include structures such as homes and businesses
in the simulation system. The team is in contact with researchers
at the National Institute of Standards and Technology who are developing
a code that simulates burning structures. Developing such a code
is a substantial task because of variations in structural materials
and their contents.
A module to represent the
process of fire spreading by showers of embers, called spotting,
will be added to HIGRADFIRETEC next year. The team is collaborating
on the module with researchers at the University of California at
Berkeley. This is not as simple as it might sound, Bradley
comments. We have to decide on the embers sizes, how
far the winds take them, and the percentage of times they start
Eventually, the team foresees
a 24-hour national wildfire prediction program being established,
with fire managers and even firefighters in the field linked to
NARAC with laptop computers.
Putting wildfire simulation
on a solid physics-based footing can only be good for firefighters,
the public, and the environment.
Key Words: Coupled
OceanAtmosphere Mesoscale Prediction System (COAMPS), fire
model, FIRETEC, geographical information systems (GIS), high-gradient
flow solver program (HIGRAD), Los Alamos National Laboratory, Lawrence
Berkeley National Laboratory, National Atmospheric Release Advisory
Center (NARAC), TeraCluster2000 supercomputer, wildfires.
For further information contact Michael Bradley (925) 422-1835 (firstname.lastname@example.org).