Improvements on the BRAMS wildfire-atmosphere modelling system

Abstract. Wildfire smoke significantly perturbs atmospheric composition and radiative balance, with implications for air quality, weather, and climate. Accurately simulating smoke–radiation–convection interactions remains a scientific challenge, particularly at meso-local scales. This study presents developments in the BRAMS v6.0 modelling system, including the integration of crown fire spread into SFIRE and dynamic coupling of fire-emitted smoke fluxes. These enhancements enable physically consistent simulations of wildfire behaviour, smoke emissions, and their radiative impacts. The model couples fire spread and heat release to compute Fire Radiative Power (FRP), which drives smoke emissions in real time. These are fully integrated with aerosol–radiation interactions and atmospheric chemistry. The system was applied to the 15 October 2017 wildfire in central Portugal using high-resolution simulations. Model performance was evaluated against MERRA-2 aerosol optical depth (AOD). Simulations reproduced key features of smoke transport and optical properties, including extinction and absorption coefficients at 400, 550, and 700 nm, as well as their spectral dependence. Results confirmed the dominance of organic carbon in extinction and validated the use of 550 nm as representative for smoke optical depth. Absorption reached 8 m⁻1 at 550 nm and led to vertical displacements of CAPE and CIN layers up to 200 m. Inversion layers responded to plume heating, exhibiting radiative lid effects that suppressed vertical mixing. These findings demonstrate the potential of the enhanced BRAMS system to simulate coupled fire–atmosphere processes, contributing to improved forecasting of smoke behavior and understanding of wildfire-induced thermodynamic and radiative impacts.