State Key Laboratory of Severe Weather, Key Laboratory of Atmospheric Chemistry of CMA, Chinese Academy of Meteorological Sciences, Beijing 100081, China; Department of Atmospheric and Oceanic Sciences, Institute of Atmospheric Sciences, Fudan University, Shanghai 200438, China.
State Key Laboratory of Severe Weather, Key Laboratory of Atmospheric Chemistry of CMA, Chinese Academy of Meteorological Sciences, Beijing 100081, China.
Sci Total Environ. 2023 Jan 20;857(Pt 3):159435. doi: 10.1016/j.scitotenv.2022.159435. Epub 2022 Oct 13.
Anthropogenic emissions reduced sharply in the short-term during the coronavirus disease pandemic (COVID-19). As COVID-19 is still ongoing, changes in atmospheric aerosol loading over China and the factors of their variations remain unclear. In this study, we used multi-source satellite observations and reanalysis datasets to synergistically analyze the spring (February-May) evolution of aerosol optical depth (AOD) for multiple aerosol types over Eastern China (EC) before, during and after the COVID-19 lockdown period. Regional meteorological effects and the radiative response were also quantitatively assessed. Compared to the same period before COVID-19 (i.e., in 2019), a total decrease of -14.6 % in tropospheric TROPOMI nitrogen dioxide (NO) and a decrease of -6.8 % in MODIS AOD were observed over EC during the lockdown period (i.e., in 2020). After the lockdown period (i.e., in 2021), anthropogenic emissions returned to previous levels and there was a slight increase (+2.3 %) in AOD over EC. Moreover, changes in aerosol loading have spatial differences. AOD decreased significantly in the North China Plain (-14.0 %, NCP) and Yangtze River Delta (-9.4 %) regions, where anthropogenic aerosol dominated the aerosol loading. Impacted by strong wildfires in Southeast Asia during the lockdown period, carbonaceous AOD increased by +9.1 % in South China, which partially offset the emission reductions. Extreme dust storms swept through the northern region in the period after COVID-19, with an increase of +23.5 % in NCP and + 42.9 % in Northeast China (NEC) for dust AOD. However, unfavorable meteorological conditions overwhelmed the benefits of emission reductions, resulting in a +20.1 % increase in AOD in NEC during the lockdown period. Furthermore, the downward shortwave radiative flux showed a positive anomaly due to the reduced aerosol loading in the atmosphere during the lockdown period. This study highlights that we can benefit from short-term controls for the improvement of air pollution, but we also need to seriously considered the cross-regional transport of natural aerosol and meteorological drivers.
在冠状病毒病大流行（COVID-19）期间，人为排放物在短期内急剧减少。由于 COVID-19 仍在持续，中国大气气溶胶负荷的变化及其变化因素尚不清楚。在这项研究中，我们使用多源卫星观测和再分析数据集，协同分析 COVID-19 封锁期间及前后中国东部（EC）多种气溶胶类型的气溶胶光学深度（AOD）的春季（2 月至 5 月）演变。还定量评估了区域气象影响和辐射响应。与 COVID-19 之前的同一时期（即 2019 年）相比，EC 地区在封锁期间（即 2020 年）对流层 TROPOMI 二氧化氮（NO）总量减少了-14.6%，MODIS AOD 减少了-6.8%。封锁期后（即 2021 年），人为排放物恢复到以前的水平，EC 地区的 AOD 略有增加（+2.3%）。此外，气溶胶负荷的变化具有空间差异。人为气溶胶为主导的气溶胶负荷的华北平原（NCP）和长江三角洲（三角洲）地区的 AOD 显著下降（-14.0%和-9.4%）。受封锁期间东南亚强野火的影响，华南地区碳质 AOD 增加了+9.1%，部分抵消了减排量。在 COVID-19 之后的时期，极端沙尘暴席卷了北部地区，NCP 地区的尘埃 AOD 增加了+23.5%，东北地区（NEC）的尘埃 AOD 增加了+42.9%。然而，不利的气象条件压倒了减排的好处，导致封锁期间 NEC 的 AOD 增加了+20.1%。此外，由于封锁期间大气中气溶胶负荷减少，向下的短波辐射通量表现出正异常。本研究强调，我们可以从短期控制中受益，以改善空气污染，但我们也需要认真考虑自然气溶胶的跨区域传输和气象驱动因素。
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