Contribution of Fire Emissions to PM2.5 and Its Transport Mechanism Over the Yungui Plateau, China During 2015–2019

Abstract

AbstractAir pollution over the Yungui Plateau (YGP) in southwestern China can be caused by the transport of biomass burning aerosols from Southeast Asia; however, the magnitude and mechanisms of such long‐range transport have not been fully investigated. Here, we studied the impacts of fire emissions on vertical PM2.5 over the YGP and the transport mechanisms of PM2.5 during the fire seasons (March–April) of the neighboring Indo‐China Peninsula (ICP) region in 2015–2019 using ground‐based monitoring data, reanalysis of meteorology, and GEOS‐Chem model simulations. Average daily PM2.5 concentrations of 36.06 ± 14.86 μg m−3 were measured at 16 ground stations in the YGP with the highest value of 53.77 μg m−3 at Xishuangbanna, the nearest station to the ICP. Model simulations showed that fire emissions contributed approximately 50%–60% of the vertical PM2.5 over the YGP at a height of 3–4 km, with larger contributions in meridional than zonal cross‐sections. Four weather patterns with low pressure over the YGP were identified as favorable conditions for smoke transport. The pattern with the lowest pressure over the northern YGP and the strongest vertical wind disturbance was the most favorable for the eastward transport of fire air pollution to the YGP. Another pattern, which had the strongest southerly wind, promoted smoke aerosols to climb from eastern Myanmar and northern Laos/Vietnam to the YGP. Through these typical pathways, ICP biomass burning significantly impacted PM2.5 pollution in southwestern China.