COVID-19 Lockdown as a Natural Experiment: Environmental and Atmospheric Responses Across India Using Multi-Sensor Data | Chapter 03 | Current Research on Geography, Earth Science and Environment Vol. 5

 

The COVID-19 lockdown in India constituted an unprecedented large-scale reduction in human mobility, industrial activity, and energy use, offering a unique geographic natural experiment to evaluate how abrupt emission controls influence atmospheric conditions across diverse environmental regions. This chapter examines spatial and regional variations in aerosol optical depth (AOD), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and ozone over India during March–June 2020, using MODIS, OMI, and MERRA-2 datasets relative to a 2014–2019 climatological baseline. By integrating satellite observations with reanalysis meteorology, the study emphasizes the geographic heterogeneity of atmospheric responses across six major regions: the Indo-Gangetic Plain, Northern, Western, Eastern, Central, and Peninsular India.

The results reveal substantial improvements in air quality across most regions, particularly over the Indo-Gangetic Plain and major urban–industrial corridors, where sharp declines in AOD, NO₂, and SO₂ were observed. These regions, characterized by dense population, intensive energy use, and constrained dispersion, showed the strongest response to reduced anthropogenic activity. In contrast, parts of Central India exhibited localized increases in aerosol loading despite overall emission reductions, illustrating the critical influence of regional meteorology. Weak winds, elevated humidity, and boundary-layer conditions in these areas promoted aerosol persistence and secondary formation, demonstrating that emission controls alone do not uniformly translate into improved air quality.

Ozone exhibited a distinctly non-uniform vertical response. Tropospheric ozone decreased across much of northern and western India, reflecting reductions in precursor emissions, while total column ozone increased modestly. This apparent divergence highlights the complexity of ozone chemistry under low-NOₓ conditions and the importance of distinguishing between surface-relevant and column-integrated ozone metrics in geographic and environmental assessments.

From a geographic and policy perspective, the findings underscore that air-quality responses to emission reductions are strongly region-dependent and closely linked to local meteorological regimes. The lockdown experience demonstrates that significant short-term improvements are achievable, but also reveals the limitations of uniform mitigation strategies across India’s diverse landscapes. Effective air-quality management must therefore integrate emission control policies with explicit consideration of regional meteorology, land-use characteristics, and atmospheric transport processes. By framing the lockdown as a spatially heterogeneous environmental experiment, this chapter contributes to broader Earth-science discourse and provides evidence-based insights to support geographically differentiated and meteorology-aware environmental policy frameworks in India.

 

Author(s) Details :-

 

Ajeet Kumar
School of Environmental Science and Engineering, Indian Institute of Technology Kharagpur, India.

 

Please see the book here :- https://doi.org/10.9734/bpi/crgese/v5/6860