Sensitivity of Grass Fires Burning in Marginal Conditions to Atmospheric Turbulence

Abstract

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 the 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 2,212 to 11,236 m2 (>400% change), driven primarily by sensitivity to initial conditions, with nonnegligible contributions from boundary condition variability during the initial 30 s of simulation. Our results highlight the need for ensemble simulations, especially when considering fire behavior in marginal burning conditions.

Fire, insect and disease‐caused tree mortalities increased in forests of greater structural diversity during drought

“…A detailed description of the physical and chemical formulations of FIRETEC can be found in Linn and Harlow (1998) and Linn et al (2002). We chose FIRETEC to perform this analysis because it has been used to model canopy‐fire spread (Hoffman et al, 2016), as well as evaluate sensitivities of fire spread to perturbation in atmospheric conditions (Jonko et al, 2021) and vegetation structure (Atchley et al, 2021). We used the model to simulate fire spread through 10 forest stands.…”

Case Analysis of Turbulence From High-Resolution Sounding Data in Northwest China

“…Owing to the lack of atmospheric data of upper troposphere and stratosphere, it is difficult for us to understand the characteristics of small-scale strongly mixed regions (Wilson, 2004). We know that the atmosphere is a chaotic system, although deterministic, it is very sensitive to the disturbance of some weather phenomena (Jonko et al, 2021). In 2020, the average precipitation in China was 695 mm, 10.3% more than that in the previous year.…”