Comparisons of High-Spatiotemporal Resolution Air Quality Modeling Systems for Simulating Prescribed Burning at Military Bases in the Southeastern United States

Accurate simulation of prescribed burning is important for the management of fires and air quality in the southeastern United States. We conducted simulations of prescribed burns in Fort Benning and Fort Stewart, Georgia with the BlueSky-CMAQ and WRF-SFIRE modeling systems and compared the results. The accuracy of the simulations is evaluated against the data collected by monitors deployed at the military bases. The effects of the simulated wind field biases are evaluated for both modeling systems.

BlueSky-CMAQ couples the BlueSky framework with the CMAQ regional air quality model. BlueSky estimates the magnitude of emissions by utilizing fuel type, fuel load, fuel moisture, and emission factors. BlueSky also estimates the vertical structure of emissions by the plume rise models it incorporates. The emissions calculated by BlueSky are provided to CMAQ, which uses them and meteorological conditions to predict the contribution of prescribed burning to local and regional air quality. In this work, we preserve the information from BlueSky including emission total mass and emission temporal profiles by utilizing them in CMAQ without the necessity for emission temporal interpolation.

WRF-SFIRE, which is typically used for wildfire simulations, captures the interactions between fire and meteorology by coupling the WRF meteorological model under LES turbulence with models of fuel moisture and fire spread. The fire model estimates fire propagation under real-time meteorological and fuel moisture conditions and has feedback to the local meteorology. The emissions time profile is estimated based on fuel consumption from the fire model results. The vertical structure of smoke is derived from buoyancy generated by the heat released from the fire. For the prescribed burning simulation, we expanded the constraint of ignition lines within WRF-SFIRE and designed ignition patterns to accurately replicate different ignition methods employed in military bases.

In this presentation, we compare the emission magnitude, emission temporal profiles, smoke plume structure, and ground-level concentrations of pollutants between the two modeling systems. Observations of winds and pollutants from monitors in military bases are used to evaluate model performance and to understand critical factors affecting simulation performance. Also, we quantitatively evaluate the impacts of the simulated wind speed and wind direction uncertainties on prescribed burning simulations for both modeling systems. The findings inform future model implementations for studying the prescribed burning impacts on regional air quality.