Characterization of near-source brown carbon emissions from 2024 Canadian ‘zombie’ fires with DSCOVR EPIC products

The fire-emitted particle-phase compounds of smoke exert significant atmospheric impacts on climate, air quality, and health, especially in downwind urban areas. Brown carbon (BrC), emitted mainly by smoldering fires and other biomass combustion, is one of the most important light-absorbing substances in atmospheric aerosol. However, the extent of absorption by BrC particles for different types of fires and the effects of BrC on the radiation budget are still largely unknown. Observational techniques alone do not provide enough constraints on the global BrC direct radiative forcing, and the current representation of BrC in climate and regional chemical transport models is either absent or overly simplistic. For example, in the majority of chemical transport models, BrC optical properties are invariant with atmospheric processing or aging. Ultraviolet and visible (UV-VIS) observations from the Earth Polychromatic Imaging Camera (EPIC) instrument on the Deep Space Climate Observatory (DSCOVR) provide comprehensive coverage and sufficient spatial and temporal resolution for constraining the BrC content of large-scale smoke events.

Here we will describe a large-scale outbreak of fires in northeastern British Columbia and northwestern Alberta, Canada that took place in early May 2024. Nearly all the fires were so-called “zombie” or “overwintering” fires that were rekindled from the remnants of large fires that occurred in the area in the late summer and fall of 2023. Smoke from this complex of fires reached the United States and resulted in unhealthy air quality as far away as Kansas City, KS. The smoke emitted by these fires was well sampled by EPIC and we will describe differences in the BrC properties of individual plumes retrieved by the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm applied to the EPIC observations. Differences will be discussed in terms of vegetation type, soil carbon content, and fire intensity. We will also note how these observations can improve chemical transport modeling of such events in the future.