Statistical aerosol properties associated with fire events from 2002to 2019 along with a case analysis in 2019 over Australia

Abstract. Wildfires are an important contributor to atmospheric aerosols in Australia and could significantly affect regional and even global climate. This study investigates the impact of fire events on aerosol properties along with the long-range transport of biomass burning aerosols over Australia using multi-year measurements from Aerosol Robotic Network (AERONET) at ten sites over Australia, satellite dataset derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), reanalysis data from Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), and back-trajectories from the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT). Strong correlation (0.62) was found between fire radiative power (FRP) and aerosol optical depth (AOD) over Australia, suggesting the significant contribution to aerosols from fires. The fire count, FRP, and AOD showed distinct and consistent interannual variations with high values during September–February (Biomass Burning period, BB period) and low values during March–August (non-Biomass Burning period, non-BB period) every year. The annual average contribution of carbonaceous, dust, sulfate and sea salt aerosols to total aerosol were 26.24 %, 23.38 %, 26.36 % and 24.02 %, respectively. The results from AERONET, MODIS, and MERRA-2 showed that AOD values significantly increased with fine mode aerosol dominated during BB period, especially in northern and southeastern Australia. Further, Carbonaceous aerosol was the main contributor to total aerosols during BB period, especially in September–December when carbonaceous aerosol contributed the most (30.08–42.91 %). The great fires during the BB period of 2019/2020 further demonstrated significant impact on aerosol properties, such as the extreme increase in AOD for most southeastern Australia, the dominance of fine particle aerosols, and the significant increase in carbonaceous and dust aerosols in southeastern and central Australia, respectively. Moreover, smoke was found as the dominant aerosol type detected at heights 2.5–12 km in southeastern Australia in December 2019 and at heights roughly from 6.2 to 12 km in January 2020. In contrast, dust was detected more frequently at heights from 2 to 5 km in November 2019, January, and February 2020. A case analysis revealed that significant changes in aerosol properties including aerosol loading, aerosol particle size, aerosol type in central Australia could be caused during the BB period of 2019/2020 due to the long-range transport of biomass burning aerosols from eastern and southern Australia.