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For each timestep (date and time specified) |
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{ |
For each fire |
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{ |
For each vertex (X, Y) |
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{ |
Get the fire environment (fuels, weather, topography) |
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Calculate fuel moistures from initial conditions |
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Calculate vertex orientation angle |
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Calculate surface fire (below) |
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if (Canopy Cover > 0) Calculate crown fire (below) |
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} |
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Preform Direct and Parallel Attacks |
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Update Raster Output Maps (arrival time, fire intensity, etc.) |
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Correct crossovers |
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Compute area and perimeter |
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} |
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} |
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Ember flight, ignition, growth from time of contact |
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Perform Indirect and Aerial Attacks |
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Merge all fires |
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{ |
Compute forward equilibrium spread rate |
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Vector wind and slope |
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Compute elliptical dimensions using resultant wind-slope vector |
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Compute spread rate R by accelerating fire over timestep |
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Compute average spread rate of fire over timestep |
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Compute spread differentials |
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Slope transformation |
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Compare fire spread with distance resolution |
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if (fire spread is truncated to distance resolution) |
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{ |
Compute time to spread distance resolution with acceleration |
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Adjust spread distance to distance resolution |
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Reduce time elapsed to accomplish distance resolution |
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} |
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} |
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{ |
Calculate Critical Surface Fire Intensity Io |
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if (actual surface intensity>= Io) |
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{ |
Compute crown fraction burned |
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Compute acceleration constant for crown fire spread |
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Compute maximum crown fire spread rate |
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Vector open wind and slope |
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Compute elliptical dimensions using resultant wind-slope vector |
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Compute critical crown fire spread rate |
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Compute actual crown fire spread rate |
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if (actual crown fire spread >= critical crown fire spread rate |
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{ |
Accelerate crown spread rate |
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Compute crown spread differentials |
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Slope Transformation |
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Compare fire spread to distance resolution |
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if (crown fire spread is truncated to distance resolution) |
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{ |
Fire acceleration as a function of distance resolution |
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Adjust spread distance to distance resolution |
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Reduce time elapsed because of increased spread rate |
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} |
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Compute Crown Fire Intensity |
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Ember Lofting from Active Crown Fire |
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} |
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else |
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{ |
Compute Crown Fire Intensity |
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Ember Lofting from Torching Trees |
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} |
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} |
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} |
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{ |
Lofting |
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{ |
Determine plume characteristics (for torching tree) |
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Loft embers |
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} |
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Flight |
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{ |
Iterate horizontal and vertical ember flight path |
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} |
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Ignition |
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{ |
Determine if ember lands inside existing fires |
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Ignition Frequency |
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} |
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} |
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