Modeling Effects of Atmospheric Stability on Wildfire Behavior

Many environmental factors contribute to the way that a wildfire behaves. Among the factors that are widely recognized as having an effect on fire behavior is local atmospheric stability. This work is focused on discerning some of the changes in the balances between various physical processes that lead to a fire's response to different stability conditions. In addition this work will increase our understanding of the ways in which ambient winds contribute to a fire's response to atmospheric stability. We will use HIGRAD/FIRETEC (a physics-based, coupled atmosphere/fire model) to simulate fires in stable and unstable atmospheric conditions under both light and strong winds. By changing the heat flux at the ground and the initial conditions in HIGRAD/FIRETEC, we will simulate the buoyancy induced mixing that is typical in unstable conditions, and the resistance to mixing that occur under stable conditions, as well as fires in both situations. The simulations will provide the opportunity to dissect the complex set of physical processes that contribute to fire behavior. By looking at phenomena such as local fire-induced winds, convective and radiative heat transfer, and wind penetration through the fire line, we will describe possible mechanisms through which stability changes a fire's intensity, rate of spread and pattern of spread. By relating the interaction between the processes to the differences in modeled fire behavior we will gain a better understanding of what role atmospheric stability might play in increasing or decreasing the potential for strong fire behavior.