Wildland fire entrainment: The missing link between wildland fire and its environment

Wildfires are growing in destructive power, and accurately predicting the spread and intensity of wildland fire is essential for managing ecological and societal impacts. No current operational models used for fire behavior prediction resolve critical fire-atmospheric coupling or nonlocal influences of the fire environment, rendering them inadequate in accounting for the range of wildland fire behavior scenarios under increasingly novel fuel and climate conditions. Here, we present a new perspective on a dominant fire-atmospheric feedback mechanism, which we term wildland fire entrainment (WFE). WFE is the fluid motion associated with air movement toward the fire driven by pressure gradients created by buoyant updrafts, and through integration of nonlocal influences on fire behavior, it plays a pivotal role in predicting wildland fire spread. WFE dynamically integrates all aspects of a fire's surrounding environment, fuels, topography, winds and fire line geometry to rate and pattern of fire spread and energy release. Because WFE explicitly incorporates fire-induced buoyancy, it links recent advances in idealized combustion research to the dynamic and highly variable wildland fire environment. Incorporating WFE into emerging fire models will allow more robust predictions of fire behavior and spread.