Many characteristics of fire behavior are a result
of interactions between a fire and its atmospheric invironment,
such as teh commonly-observed bowing of firelines into
"fingers", the extreme behavior of fires that burn street
patterns through fuel while leaving nearby forest untouched,
as well as dangerous blowups, in which burning rates and
spread rates suddenly increast dramatically
Three principal environmental factors that affect
wildland fire behavior are:
- Fuel: types, characteristics (moisture, size, shape),
fuel loading, horizontal continuity and vertical arrangement,
species
- Weather: wind, temperature, RH, precipitation, Weather
Changes (cold fronts, foehn winds, thunderstorm downdrafts,
sea/lans
breezes, diurnal slope winds)
- Topography: aspect towards sun, slope features like bos
or narrow canyons, barriers like creeks, roads, rockslides,
unburnable fuel
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Wind and Slope Effects
- Changes in wind and slope cause variations in
fire behavior
- Current operational models incorporate these variables
in a non-interactive manner (Note: Current operational
models cannot predict rapid changes in fire behavior, blowups,
that lead to sever fire
behavior, or firefighter safety problems)
- The next generation of fire models for operations and
planning MUST incorporate realistic firem wind and terrain
interactions
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Effect of fire-atmosphere
coupling pulling a fire into fingers (right)
- Onion sage brush fire in Owens Valley, CA 1985 courtesy
of C. George
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Street Patterns Observed in Fires (left)
- Effect of fire-induced vortex dynamics
- Yellow regions indicate burn
- Photo courtesy Brenner; observed in Florida
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