Impacts of a New Multilayer Fuel Consumption Model on Heating, Emissions and Pyrocumulonimbus Production in WRF-SFIRE-CHEM

Extreme wildfires have increasingly become a frequent and devastating phenomenon across the western United States and Canada in recent years. These fires not only pose a direct threat to ecosystems and communities but also generate significant atmospheric disturbances. One of the most impactful phenomena associated with large wildfires is the formation of pyrocumulonimbus (pyroCb) clouds—fire-triggered thunderstorms that can inject massive quantities of smoke and particulate matter into the lower stratosphere. This can have long-lasting effects on both regional and global climate systems.

Simulating wildfires and their atmospheric impacts presents a significant challenge, especially within large-scale global climate models and regional weather forecasting systems. The difficulty arises due to the complexity of surface emissions, the variability in fuel types, and the dynamic nature of fuel consumption during fire events. In this study, we employ the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) and the SFIRE fire spread model to improve the simulation of wildfire emissions and their subsequent impact on air quality. The SFIRE model incorporates a multi-layer approach to fuel consumption, including new parameterizations for pyrolysis and smoldering phases, which are critical for accurately representing fire behavior.

Our analysis focuses on the sensitivity of different fuel consumption rates for different fuel classes within the WRF-SFIRE-Chem framework, particularly in their ability to simulate heat fluxes and emissions. We apply this enhanced modeling approach to the California Creek Fire of 2020, one of the state's largest and most intense wildfire events. The presentation will delve into the interplay between fire heat flux, fuel consumption rates, pyroCb generation, and their impacts on regional air quality, providing insights into the broader implications for public health and climate interactions in the region.

This work was performed under the auspices of the U.S. DOE by LLNL under contract DE-AC52-07NA27344. LLNL-ABS-868865