The World Health Organization (WHO) declared the coronavirus disease of 2019 (COVID-19) as a pandemic due to its widespread global infection. This has resulted in lockdown under different phases in many nations, including India, around the globe. In the present study, we report the impact of aerosols on surface ozone in the context of pre-lockdown (01st - 24th March 2020 (PLD)), lockdown phase1 (25th March to 14th April 2020 (LDP1)), and lockdown phase 2 (15th April to 03rd May 2020 (LDP2)) on clear days at a semi-arid site, Anantapur in southern India using both in situ observations and model simulations. Collocated measurements of surface ozone (O3), aerosol optical depth (AOD), black carbon mass concentration (BC), total columnar ozone (TCO), solar radiation (SR), and ultraviolet radiation (UV-A) data were collected using an Ozone analyzer, MICROTOPS sunphotometer, Ozonometer, Aethalometer, and net radiometer during the study period. The diurnal variations of O3 and BC exhibited an opposite trend during three phases. The concentrations of ozone were ∼10.7% higher during LDP1 (44.8 ± 5.2 ppbv) than the PLD (40.5 ± 6.0 ppbv), which mainly due to an unprecedented reduction in NOx emissions leading to a lower O3 titration by NO. The prominent increase in the surface zone during LDP1 is reasonably consistent with the observed photolysis frequencies (j (O1D)) through Tropospheric Ultraviolet and Visible (TUV) model. The results show that a pronounced spectral and temporal variability in the AOD during three lockdown phases is mainly due to distinct aerosol sources. The increase in AOD during LDP2 due to long-range transport can bring large amounts of mineral dust and smoke aerosols from the west Asian region and central India, and which is reasonably consistent with the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) air mass back trajectories and Moderate Resolution Imaging Spectroradiometer (MODIS) fire counts analysis over the measurement location. Overall, a drastic reduction in BC concentration (∼8.4%) and AOD (10.8%) were observed in the semi-arid area during LDP1 with correspondence to PLD. The columnar aerosol size distributions retrieved from the spectral AODs followed power-law plus unimodal during three phases. The absorption angstrom exponent (AAE) analysis reveals a predominant contribution to the BC from biomass burning activities during the lockdown period over the measurement location.

中文翻译：

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印度南部 COVID-19 大流行期间气溶胶对地表臭氧的影响：来自地面和卫星观测以及模型模拟的多仪器方法

世界卫生组织 (WHO) 宣布 2019 年冠状病毒病 (COVID-19) 因其在全球广泛感染而成为大流行病。这导致全球许多国家（包括印度）在不同阶段实施封锁。在本研究中，我们报告了在封锁前（2020 年 3 月 1 日至 24 日（PLD））、封锁阶段 1（2020 年 3 月 25 日至 4 月 14 日（LDP1））和封锁阶段 2 的背景下气溶胶对地表臭氧的影响（2020 年 4 月 15 日至 2020 年 5 月 3 日 (LDP2)）在晴朗的日子里，在印度南部阿南塔普尔的一个半干旱地区，使用原位观测和模型模拟。地表臭氧 (O3)、气溶胶光学深度 (AOD)、黑碳质量浓度 (BC)、总柱状臭氧 (TCO)、太阳辐射 (SR) 和紫外线辐射 (UV-A) 数据的并置测量是使用臭氧分析仪，研究期间的 MICROTOPS 太阳光度计、臭氧计、空气湿度计和净辐射计。O3和BC的日变化在三个阶段表现出相反的趋势。LDP1 (44.8 ± 5.2 ppbv) 期间的臭氧浓度比 PLD (40.5 ± 6.0 ppbv) 高约 10.7%，这主要是由于 NOx 排放量空前减少导致 NO 对 O3 的滴定降低。LDP1 期间表面区域的显着增加与通过对流层紫外线和可见光 (TUV) 模型观察到的光解频率 (j (O1D)) 相当一致。结果表明，在三个锁定阶段，AOD 的明显光谱和时间变化主要是由于不同的气溶胶来源。LDP2期间由于远距离传输导致的AOD增加可带来大量来自西亚地区和印度中部的矿尘和烟雾气溶胶，这与混合单粒子拉格朗日综合轨迹（HYSPLIT）气团相当吻合返回轨迹和中分辨率成像光谱仪 (MODIS) 对测量位置的火灾计数分析。总体而言，在 LDP1 期间，与 PLD 相对应，在半干旱地区观察到 BC 浓度 (~8.4%) 和 AOD (10.8%) 急剧下降。从光谱 AOD 中检索到的柱状气溶胶尺寸分布在三个阶段遵循幂律加单峰分布。