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Sensitivity of grass fires burning in marginal conditions to atmospheric turbulence

Author(s): Alexandra K. Jonko, Kara M. Yedinak, Juliana L. Conley, Rodman Linn
Year Published: 2021

Atmospheric forcing and interactions between the fire and atmosphere are primary drivers of wildland fire behavior. The atmosphere is known to be a chaotic system that, although deterministic, is very sensitive to small perturbations to initial conditions. We assume that as a result of the tight coupling between fire and atmosphere, wildland fire behavior, in turn, should also be sensitive to perturbations in atmospheric initial conditions. Observations suggest that low intensity prescribed fire, in particular, is susceptible to small perturbations in the wind field, which can significantly alter fire spread. Here we employ a computational fluid dynamics model of coupled fire-atmosphere interactions to answer the question: How sensitive is fire behavior to small variations in atmospheric turbulence? We perform ensemble simulations of fires in homogenous grass fuels. The only difference between ensemble members is the state of the turbulent atmosphere provided to the model throughout the simulation. The atmospheric state is a function of initial conditions applied at the start of the simulation and boundary conditions applied throughout the simulation. We find a wide range of outcomes, with area burned ranging from 2212 m2 to 11236 m2 (>400% change), driven primarily by sensitivity to initial conditions, with non-negligible contributions from boundary condition variability during the initial 30 seconds of simulation. Our results highlight the need for ensemble simulations, especially when considering fire behavior in marginal burning conditions.

Citation: Jonko, Alexandra K.; Yedinak, Kara M.; Conley, Juliana L.; Linn, Rodman R. 2021. Sensitivity of grass fires burning in marginal conditions to atmospheric turbulence. Journal of Geophysical Research: Atmospheres 126(13):e2020JD033384 https://doi.org/10.1029/2020JD033384
Topic(s): Fire Behavior, Simulation Modeling, Weather, Fuels, Fuel Treatments & Effects, Prescribed Fire-use treatments
Ecosystem(s): None
Document Type: Book or Chapter or Journal Article
NRFSN number: 23413
FRAMES RCS number: 63824
Record updated: Aug 4, 2021