Effects of Fuel Moisture Content on Smoke Plume Dynamics

Smoke plumes generated by wildland fires (i.e., wildfires and prescribed burns) significantly impact air quality, public health, and ecosystems by transporting pollutants over long distances. Consequently, understanding the dynamics of smoke dispersion is essential for mitigating these environmental impacts and for improving predictive smoke behavior models. Among the various factors that influence plume behavior, fuel moisture content (FMC) plays a critical role. FMC, defined as the water content in vegetation, exhibits pronounced diurnal and seasonal variability, which in turn affects combustion processes by regulating both the energy released and the emissions produced.

Fuel-scale studies have largely focused on how FMC affects early-stage plume development, focusing on the near-surface behavior and excluding broader atmospheric influences. This study uses large eddy simulations to examine FMC's effects on plume rise, structure, and downwind dispersion within the convective atmospheric boundary layer. Results indicate that higher FMC produces a less buoyant plume that remains confined to the convective mixed layer, resulting in shorter, wider plumes with enhanced vertical dispersion. In contrast, lower FMC generates more buoyant plumes that penetrate the stable layer above the inversion, leading to reduced lateral and vertical spreading but faster downwind transport. These findings provide guidance for smoke forecasting, prescribed burn planning, and mitigation strategies.