CALIPSO-observed Southeast Asia biomass-burning influences on aerosol vertical structure in Guangdong-Hong Kong-Macao Greater Bay Area

Southeast Asia (SEA) biomass-burning could exert considerable influences on air quality and stability in the Guangdong-Hong Kong-Macao Great Bay Area (GBA) through long-range transport, while such impacts were typically quantified with numerical modeling which may suffer uncertainties in emissions and model parameterizations. Here we present an observation-based method to quantify such influences of SEA biomass-burning by analyzing 2009–2019 satellite-observed aerosol vertical structure which has enough data records to distinguish the conditions with or without severe biomass-burning impacts based on fire point counts in SEA. Results suggest that the observation-based method successfully captured the SEA biomass-burning days in spring, excluding the irrelevant days as more as possible and avoiding underestimation. Substantial increase of aloft AOD (by 0.21) in GBA is found during the severe SEA biomass-burning days comparing to less severe days, suggesting the enhanced aerosol loading in GBA contributed from the SEA biomass burning. Meanwhile, the near-surface particle size in GBA was increased (CR from 0.606 to 0.673) during severe SEA biomass-burning days, which is opposite to that for the aloft particle size which was decreased (CR from 0.693 to 0.621) driven by the small aerosols originated from biomass-burning SEA. Such phenomenal might be associated with the enhancement of atmospheric static stability in GBA (N2 from 1.34 × 10−4 s−2 to 1.66 × 10−4 s−2) as the abundant aloft aerosols transported from SEA modulates the aerosol vertical structure and associate radiative effects and atmospheric dynamic, results in enhanced aging processes and aerosol particle aggregation under weak ventilation condition. Further, the air pollution in GBA is also aggravated due to the reduced ventilation driven by the enhanced aerosol radiative effects associated with the transported aerosols, as the surface PM2.5 concentrations were increased by 17% (from 29.27 μg /m3 to 34.15 μg /m3) during severe biomass-burning days. Such results demonstrate that our observation-based method with abundant satellites-retrieved aerosol vertical structure information can successfully quantify the influences of SEA biomass-burning on aerosol–radiation interactions and local air pollution over the GBA, which can also be applied in other regions to identify the influences of local sources and regional transport pollution.