A novel framework for assessing regional wildfires contributions to biomass burning aerosol optical depth

Abstract. Biomass burning (BB) aerosol significantly affects climate by altering the radiation budget and atmospheric chemistry. Accurate source estimation is vital for climate modeling, yet global observations remain scarce. This study introduces a novel framework for assessing the contribution of transported BB aerosol to smoke-associated aerosol optical depth (BB AOD) at selected locations. The approach integrates satellite fire data (Moderate Resolution Imaging Spectroradiometer Active Fire Product) with air parcel trajectory models (HYSPLIT), aerosol transport models (NAAPS), BB emissions (FLAMBE), and plume rise (CAMS GFAS). Tested in Warsaw (Poland, Central Europe) over 2006–2022, the methodology reveals a prominent influence of long-range BB aerosol transport from North America. Analysis indicates that USA (without Alaska) (37.3 %±3.4 %), Canada (25.4 %±6.7 %) and the Alaska (2.6 %±2.1 %) together contribute approximately 65 % of BB AOD during the BB season in the Northern Hemisphere, surpassing nearer European sources. Among European regions, Eastern Europe accounts for 16.6 %±5.3 % of BB AOD, followed by the Iberian Peninsula (10.6 %±1.5 %) and Southern Europe (7.5 %±2.1 %). Incorporating vertical plume dynamics is crucial: a planetary boundary layer plume-top threshold underestimates Canadian contribution while overestimating European sources, whereas removing altitude constraints overestimates Canadian influence. These findings underscore the importance of transatlantic transport, plume-rise processes, and vertical aerosol distribution in regional climatology. The presented framework for assessing BB AOD contributions is universal and can be applied at any location. Future work should incorporate the specific aerosol types emitted during BB events and their aging processes.