Collaborative Research: Predictive Understanding of Wildfire Spotting and Smoke Transport within the Atmospheric Boundary Layer

The rapid spread of wildfires and associated smoke plumes undermines the health and safety of communities, the effectiveness of firefighting efforts, and complicates the evacuation of residents. This project aims to gain predictive understanding of the physical processes for rapid wildfire spreads. This will help to guide firefighters to more safely and effectively suppress fires with an improved adaptation to diverse surrounding atmospheric conditions. The predictive understanding of the environment conditions conductive to re-entry of smoke plumes back to the ground will help develop new tools and engage the community of practitioners to open the “window of prescription” for prescribed fire. This project will engage with national training center workshops to demonstrate the impact of fire-generated turbulent flows on surface smoke dispersion, spotting, and fire spread. Local and regional agencies will be exposed directly to new developments in wildland fire research through workshops and site visits. This project will train two Ph.D. students and a postdoc in fields of atmospheric dynamics, modeling, and data science. The research findings will be communicated to the science community via peer-reviewed publications and to college students via classroom teaching and curriculum development. The innovation of this project lies in the consolidation of common characteristics between two distinct phenomena—naturally occurring density currents and fire-generated warm plumes. This allows for a direct application of the physical understanding of observed large-scale turbulent flows in naturally occurring density currents to the rapid growth of billows in fire smoke plumes by considering additional physical factors that are unique to fire-generated plumes, such as non-hydrostatic conditions and thermal expansion. The central hypothesis of this research links rapid advancement of wildfires to the rapid non-modal growth of large-scale Kelvin-Helmholtz billows beneath fire-generated buoyant plumes. In concert with the continuous surface fire spread, spotting occurs as airborne burning embers enter large-scale billow-like turbulent eddies within smoke plumes. The rapid falling of airborne burning embers back to the ground ignite new fires at a considerable distance downstream from the existing fire front. Additionally, under conducive environmental conditions, successive large-scale billow-like turbulent eddies can cause elevated smoke concentration near the ground over considerable distances from the prescribed fire site. This project will perform non-modal instability analysis of fire smoke plumes to delineate the key processes responsible for rapid growth of billow-like large-scale turbulent flows under different environment conditions. The research team will utilize large-scale eddy simulations to validate the results of non-modal instability analysis and investigate their underlying dynamics and thermodynamic processes. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.