Abstract:

Fire suppression activities in the past few decades in North America have led to higher fuel accumulations, which coupled with shifting hydroclimatic patterns has led to an increase in frequency and severity of wildland fires. Prescribed fires and fuel treatments such as mechanical thinning are deemed to be effective tools to manage fuel loads and establish a higher degree of control over landscape management and restoration against catastrophic mega fires. However, assessing the effectiveness of fuel treatments is rendered complicated due to several factors such as wind, fuel moisture, and fire-atmospheric interactions at the fine scales. The present work explores these issues by using physics-based simulations and data analysis from novel experiments while varying the degrees of fuel treatments and fuel moisture, as observed during different stages of fuel management. Systematically varying these parameters yield widely different fire behavior patterns. Detailed analyses on turbulent heat and energy exchange are conducted to understand the fundamental processes governing varying regimes of fire intensity, fire spread, ember transport, and fuel consumption under different conditions of fuel moisture and treatment. The conclusions are generalized to highlight the importance of considering vegetation response to hydrometeorological events, coupled with fine-scale fire-atmosphere interactions while managing wildland fire behavior. On the other hand, wildland fires themselves are characterized by their own weather which is driven by both shear and buoyancy-driven turbulence. They also act as a local source for scalars, namely greenhouse gases (such as carbon dioxide and water) and soot particles as resultants of the ignition process. In this talk, we will explore the complex turbulent dynamics of wildfire propagation using the tools of micrometeorology. Insights into the energetics of turbulent exchange processes during fire propagation will lead to a better understanding and improved models for wildland fire behavior.