By Chi Chau and Matt McKnight

Wildfire

Problems

In 2000 alone, wildfires were responsible for an estimated $10 billion in damages

Firefighter safety Loss of Biomass

Wildlife habitat National Parks

Smoke, air pollution, fires destroy ground cover resulting in soil erosion and mudslides when it rains. Long term effects on the environment Global Warming

CO2 is produce when plants burn effect global warming

Nature of wildfires

Reduce fuel buildup and help prevent even bigger fires

Improve soils for healthier trees Cycle of nature

Interesting facts

Fire and atmosphere influence each other significantly

Scientists have found that a wildfire’s shape starts out the same everywhere in the world

Modeling

Simulators have been around for half a century starting with simple solvers on simple hardware

The goal has always been to produce the most accurate predictions using the most current data. It is obvious that atmospheric conditions are

inextricably linked to wildfire behavior. The atmospheric-wildfire model becomes the

standard of simulation As it turns out, changing heat from the fire feeds back

to the atmosphere producing “fire winds”, while already occurring winds are feeding the fire.

Data Fire location

Temperature Direction of spread

Weather data Wind When will it RAIN??

Fuel Rate of burn

Topological information Elevation Slope Aerial photography

Map Information Towns Roads Forested/Non Forested lines

Atmospheric Modeling “The Fifth-Generation NCAR / Penn State Mesoscale

Model (MM5) is the latest in a series that developed from a mesoscale model used by Anthes at Penn State in the early 70's that was later documented by Anthes and Warner (1978). Since that time, it has undergone many changes designed to broaden its usage. These include

(i) a multiple-nest capability, (ii) nonhydrostatic dynamics, which allows the model to be

used at a few-kilometer scale(iii) multitasking capability on shared- and distributed-

memory machines(iv) a four-dimensional data-assimilation capability, and (v) more physics options. “

Wind and Slope

As wind feeds a fire, the fire creates wind of it’s own. These winds can be very high speed (20 – 30 m/s)

Burning embers A Fire’s flanks might split and burn separately The Fire moves uphill much faster than downhill Changes in wind and slope affect the behavior of

your model

Wildfire model in action

Here is the model shows a fire’s shape and behavior

What does the model show?

Assume the model is on a perfectly flat land, the arrows at the bottom of the box represent the wind, blowing from left to right.

Fire model cont

Next, let’s say the fire suddenly ignites for whatever reason. The fire quickly takes on the shape of a triangle and the hottest spot is its head. Due to the wind (remember the arrow represent the wind) blowing from left to right it push the fire forward. The fire’s sides are parallel to the wind. The flames creep slowly against the wind.

Wildfire model cont

The combustion of tress and grasses releases intense heat and quickly warms the atmosphere. Since the hot air rises, forming powerful updraft winds. More air is drawn into the fire from all directions.

Wildfire model cont

Watch out! After certain time, the fire leaps forward into new

fuels and the fire’s path is widened. At this point, the wildfire is changing weather

that is already there As known as phenomenon wildfire weather. Good for BBQ !

How is the model useful?

Computer model help us understand interesting and erratic fire behaviors.

Help us evaluate the threats and benefits of wildfires

Linking fire and atmosphere model

Coupled Atmosphere-Fire Model by Clark

Coupled Atmosphere-Fire Model

Winds play a critical role in fire spread, so by combining Atmosphere and Fire model it gives us a good prediction.

“Forest fires (wildfire) are very complex phenomena … Interactions between forest fires and airflow are highly nonlinear, unstable and their radiation and combustion properties are not fully understood” said Clark.

Atmosphere-Fire model cont

The model helps to explain a commonly observed trait of wind-driven fires, the growth of fingers of flame, space about a kilometer apart which form the main fire line.

Previous research (w/o the model) proposed that he fingering was due to variations in either the fire’s fuel or the local geography.

But, the model suggests that when winds are weak, a fire line several km or more in length inherently unstable and very likely to break up into fingers.

Massive computing

Using OpenMP or multigrid we can make the solver very fast as well as running multiple independent simulations on single nodes

Now many users at different areas of the fire have access to individual decision-making tools.

Continued

Smoke can obscure ‘naked-eye’ observations but can be overcome by infrared sensitive video

Aerial photography can bring accurate information from rough terrain that might be inaccessible.

Autonomous detectors When they stop transmitting, you’ve found the fireline. Can also contain other sensors

References

http://box.mmm.ucar.edu/fire/model/model_whyc.html

http://www.mmm.ucar.edu/mm5/overview.html

http://www-math.cudenver.edu/~jmandel/fires/Fires-Kluwer.pdf

http://www.ucar.edu/educ_outreach/wildfire/model.htm

http://box.mmm.ucar.edu/fire/model/model_home.html

http://www.scd.ucar.edu/info/SC96/FIRE/FireExhibit.html