Sensitivity of Burned Area and Fire Radiative Power Predictions to Containment Efforts, Fuel Density, and Fuel Moisture Using WRF‐Fire

Abstract

Predicting the evolution of burned area, smoke emissions, and energy release from wildfires is crucial to air quality forecasting and emergency response planning yet has long posed a significant scientific challenge. Here we compare predictions of burned area and fire radiative power from the coupled weather/fire‐spread model WRF‐Fire (Weather and Research Forecasting Tool with fire code), against simpler methods typically used in air quality forecasts. We choose the 2019 Williams Flats Fire as our test case due to a wealth of observations and ignite the fire on different days and under different configurations. Using a novel re‐gridding scheme, we compare WRF‐Fire's heat output to geostationary satellite data at 1‐hr temporal resolution. We also evaluate WRF‐Fire's time‐resolved burned area against high‐resolution imaging from the National Infrared Operations aircraft data. Results indicate that for this study, accounting for containment efforts in WRF‐Fire simulations makes the biggest difference in achieving accurate results for daily burned area predictions. When incorporating novel containment line inputs, fuel density increases, and fuel moisture observations into the model, the error in average daily burned area is 30% lower than persistence forecasting over a 5‐day forecast. Prescribed diurnal cycles and those resolved by WRF‐Fire simulations show a phase offset of at least an hour ahead of observations, likely indicating the need for dynamic fuel moisture schemes. This work shows that with proper configuration and input data, coupled weather/fire‐spread modeling has the potential to improve smoke emission forecasts.

Sensitivity of Simulated Fire‐Generated Circulations to Fuel Characteristics During Large Wildfires

“…While some efforts have been made to improve this representation by adjusting fuel categories via machine learning (DeCastro et al., 2022; Lee et al., 2023) and accounting for canopy fuels through addition of crown fire heat and improved heat release schemes (Shamsaei et al., 2023b; Turney et al., 2023), the foundation of both the Anderson 13 and SB40 fuel data is surface fuels in LANDFIRE, which appears to underrepresent real‐world fuel loads available for consumption in large fires. Such fuel availability is directly linked to wildfire energy release (Goodwin et al., 2021).…”

“…Our approach for adjusting fuel loads is similar to that used in Turney et al. (2023), wherein WRF‐Fire's surface fuel loads were adjusted to a categorical ∼10 kg m −2 in forested regions based on FINN (Fire Inventory from NCAR, Wiedinmyer et al., 2011) in order to “correct fuel density burning on average rather than explicitly accounting for canopy fires.” Similar approaches were also employed in Lee et al. (2023) in order to account for augmented fuel loads due to beetle killed trees in the central Sierra Nevada during the Creek fire.…”