What's New in FARSITE 4.0

It's Faster

FARSITE version 4.0 is multi-threaded. This means that the FARSITE program can be divided into pieces that run separately. Multi-threading is used to separate the fire growth simulation from the interface and to allow the fire growth calculations in FARSITE to make use of more than one processor. For example, if you have a dual-processor computer, you can select to use all processors which will speed the computations considerably. If you only have a single processor computer, multi-threading still has advantages:

 

  • The interface (clicking buttons, typing in dialog box boxes, etc.) is separated from the simulation (all the number crunching going on behind the scenes). This means that when a simulation is running and you click on the stoplight button, something happens right away. No more wondering if the program "heard" you, then clicking again or trying some other command until everything catches up with you and you've made a mess of your simulation.

  • If you have more than one Pentium chip in your computer, FARSITE can use all of the processors by parallelizing some of the fire growth calculations (dividing the process into pieces for each chip to run simultaneously).

  • You can work on other things in FARSITE like file editing while your simulation is running. But remember, this other work takes computer horsepower away from the running simulation, slowing it down.

  • The improved dead fuel moisture model does all it's calculations at the beginning of a simulation. Once this is done the rest of the simulation goes much faster. You can even save the fuel moistures in a file (it's done automatically in a bookmark) to let future simulations skip the fuel moisture calculations.

 

Interface Improvements

A new "Simulation Legend" window puts all the display and settings information for a simulation in one place. The "Simulation Settings" window shows all the input files, parameters, and option settings in an expandable tree list. The visible theme and attached vector files have a ArcView style legend. Double clicking on these legends then brings up a color/style picker.

You can now query the fire perimeter as well as querying the landscape. A list of fire behavior characteristics is displayed. Segments of the fire perimeter can be moved, modified, or deactivated.

The ASCII input files now have custom editors. These make it easier to edit files or create new ones using text boxes and duplication utilities.

Up & Down Slope Winds

Up and down slope winds can be specified in the Wind (.WND) File for any line(s) in the file. Specifying up slope or down slope winds only uses the slope at individual points in the slope theme of the Landscape (.LCP) File. It will not simulate complex terrain influenced winds such as up canyon winds.

Improved Dead Fuel Moisture Model

An improved dead fuel moisture model (see fuel moisture in the Technical Documentation) is used. To implement the Post-Frontal Combustion model, all sizes of dead fuel and duff have fuel moistures calculated. This new model has much better sensitivity to rain and solar radiation so the simulated fire behavior is more responsive to the terrain, shading, and vegetative cover.

The new moisture model is implemented spatially for any time step in the simulation. Using the Output > Environmental Map command, a raster image of environmental data can be displayed. Maps of fuel moisture for any of the dead fuel size classes and duff can be generated, as well as weather and wind parameters. These maps are very useful for visualizing the weather and fuel moisture environment of the simulation.

A new feature is the Conditioning Period which allows fuel moistures to be calculated prior to the start of the simulation. This way you can bring the initial fuel moistures into equilibrium with the environment. Now you don't have to trick the computer into calculating fuel moistures before the fire simulation begins.

The New Post-Frontal Combustion Model

This new "Burnup" model simulates the burnout of woody fuels and duff behind the flaming front. A time dependent combustion history for both flaming and smoldering burning is built. This allows the smoke and/or heat production to be displayed for all or part of the fire simulation area.

However this model requires additional data. Ideally duff loading and large woody fuel (3"+) GIS themes should be used to feed this model. But landscape wide constants can be used if the user is willing to ignore the variability of heavy fuels. The Post Frontal Combustion model is very computer and data intensive, thus requiring very long simulation run times. This information is probably more useful for prescribed fire planning, rather than simulations of ongoing fires.

Setting a Burning Period

Specific daily burning periods can now be identified in FARSITE 4.0. A optional ASCII text file of dates and times is used to stop the simulation during periods of low activity, such as cool, moist nights or rainy periods. It helps correct the tendency of FARSITE to over-predict under moderate burning conditions because long periods of very low fire behavior can result in significant spread distances.

This feature can also be used to speed up simulations by "turning off" the simulation during periods of low fire behavior that have little effect on the final results.

 

 

Measuring Landscape Distances

FARSITE 4.0 can measure distances in the "LANDSCAPE" window  with the new View > Measure Landscape Distances command.

This feature can also be used to display a profile window along a selected line. This profile window can provide much of the data needed for RERAP transects.

 

 

Setting Up Attack Groups

Attack crews can now be formed up into groups which can be used for attacks. The line production rates for all the resources in a group are added together. This saves building fictitious crews to simulate larger attacks.