Aerosols greatly impact the global and regional climate system and public health. We conducted lidar measurements at Wuhan (30.53°N, 114.37°E) from October 2010 to June 2020 and analyzed the massive dataset with an automatic lidar processing algorithm, to investigate the long-term variations of aerosols. Lidar-derived total aerosol optical depth (AOD) at 532 nm shows an interannual decrease of −0.049 since 2010. Compared with AODs in other megacities worldwide, the AOD for Wuhan shows the largest decrease rate. After separating AOD contributions from boundary layer (BL) and free troposphere (FT), different evolution patterns are revealed with AOD decrease rates of −0.009 and −0.044 per year for FT and BL, respectively, which indicates more than 80% of AOD decrease are associated with reductions of local emissions. In addition, BL AOD was always larger than FT AOD before COVID-19 lockdown. However, this relation was conversed thereafter, with the lowest value of 0.125 for BL AOD since 2010, which is only the half of FT AOD within the same period. This feature corroborates strong influences of COVID-19 lockdown on human activities and local emissions. These findings can improve our understandings of regional aerosol responses to pollution controls and aerosol direct impacts on regional climate.

气溶胶极大地影响了全球和区域气候系统以及公共卫生。我们于 2010 年 10 月至 2020 年 6 月在武汉（30.53°N，114.37°E）进行了激光雷达测量，并使用自动激光雷达处理算法分析了海量数据集，以研究气溶胶的长期变化。激光雷达衍生的 532 nm 总气溶胶光学深度 (AOD) 自 2010 年以来年际下降 -0.049。与全球其他特大城市的 AOD 相比，武汉的 AOD 下降率最大。从边界层（BL）和自由对流层（FT）中分离出 AOD 贡献后，显示出不同的演化模式，FT 和 BL 的 AOD 每年下降率分别为 -0.009 和 -0.044，这表明 AOD 下降率超过 80%与减少当地排放有关。此外，在 COVID-19 锁定之前，BL AOD 始终大于 FT AOD。但此后此关系发生逆转，BL AOD 为 2010 年以来的最低值 0.125，仅为同期 FT AOD 的一半。这一特征证实了 COVID-19 封锁对人类活动和当地排放的强烈影响。这些发现可以提高我们对区域气溶胶对污染控制的响应和气溶胶对区域气候的直接影响的理解。