Interactive Fire Emissions Coupled with Climate and Chemistry in GFDL’s Earth System Model version 4.1

Fire plays a critical role in the Earth system, both as a driver and responder to climate change. Variations in vegetation cover and ignition patterns, influenced by climate, affect fire behavior, while fire emissions impact climate by altering radiative fluxes and cloud properties. Despite these interactions, most global climate models fail to fully represent the dynamic interplay between vegetation, fire, and climate. In this study, we leverage the prognostic fire module from GFDL’s Land Model (LM4.1), which includes dynamic vegetation processes, to interactively calculate biomass burning emissions and injection heights. Emissions are then coupled with the atmospheric chemistry and aerosol component (AM4.1) in GFDL’s Earth System Model version 4.1 (ESM4.1). The model calculates fire radiative power (FRP) from fire spread rates and fuel content, using it alongside atmospheric parameters like boundary layer height and Brunt-Väisälä frequency in the Sofiev injection height scheme. Fire emissions are calculated using carbon release rates from biomass estimated by the land model and emission factors from Akagi et al. (2011) and Andreae and Merlet (2001), and these emissions are integrated directly into the atmospheric model for interactive coupling. 

We conducted a coupled simulation in AMIP mode and compared the modeled emissions with the observation-based Global Fire Emissions Database (GFED4.1s). Preliminary results show a promising agreement for global fire emissions of trace gases and aerosols during the 1997–2014 period, with seasonal variability falling within the error margins of observed emissions. We then compared results from interactive fire emissions experiment with a fixed fire emission experiment to analyze the direct radiative effects of fire-emitted aerosols. By treating fire emissions as an interactive component of the Earth system, rather than as a prescribed external forcing, this approach enables a more comprehensive representation of fire-climate feedback and enhances the assessment of radiative effects from fire aerosols.