Evolution of tropospheric aerosols over central China during 2010-2024 as observed by lidar

Abstract

Air quality in China has improved significantly over the past decade. However, recent studies show that this progress has notably slowed in recent years. To investigate regional patterns and driving factors, we examined the long-term evolution of tropospheric aerosols over Wuhan (30.5° N, 114.4° E) from 2010 to 2024, using ground-based polarization lidar observations. Aerosol optical depth (AOD) trends are divided into two phases: a declining trend (−0.077 yr−1) during 2010-2017 (Stage I) and a fluctuating period during 2018-2024 (Stage II). Contributions from natural (dust) and anthropogenic (non-dust) aerosols were analyzed separately. Dust optical depth (DOD) consistently declined (−0.011 yr−1) until August 2020 and became larger again after-wards. In Stage I, anthropogenic aerosols (−0.068 yr−1) were responsible for 88.3 % of the total AOD reduction, primarily due to decreases in boundary-layer AOD. In Stage II, anthropogenic AOD fluctuated, possibly due to atmospheric chemistry and meteorological factors. Seasonal variations were also observed. Anthropogenic aerosols appeared from the surface to 2.5 km in summer, with particle extinction and mass concentration of 0.12 km−1 and 83.0 µg m−3, which were concentrated below 0.7 km in winter, with much higher particle extinction and mass concentration of 0.31 km−1 and 211.8 µg m−3. Two case studies highlighted typical pollution events: summertime transboundary agricultural biomass burning smoke in June 2014 and wintertime local anthropogenic aerosol pollution in January 2019. These findings improve our understanding of how regional aerosols respond to local emission controls and long-range transport of dust and smoke.