Downwind deposition of pyrogenic particles from wildfire plumes

Wildfires emit vast quantities of intermediate-sized airborne particles (10-2000 µm) that can influence ecosystem processes, yet the generation, transport, and deposition of these particles remain poorly quantified. We develop a physics-based framework that simulates pyro-generation, convective lofting, downwind transport, and ballistic deposition of such particles, thereby characterizing a previously understudied wildfire deposition footprint. Fire sensible heat release drives a convective plume that lofts particles to heights determined by their size, shape, and density, after which they are released into prevailing winds and ballistically deposited. We evaluate the framework results using a unique dataset of particle deposition collected 3-40 km from the fire line during the 2021 Caldor Fire. Observed fire spread, fuel conditions, and meteorology provide inputs for preliminary model testing. Model predictions show strong agreement with measured pyrogenic deposition patterns. This framework offers a pathway for anticipating and quantifying downwind deposition of wildfire-emitted particulate material on ecosystems. Sensible heat release from wildfires drives a convective plume which raises airborne particles into the air before being released and transported by prevailing winds, according to a physics-based framework utilizing deposition data from 2021 Caldor fire line