Temporal and spatial variability in aerosol optical depth (550 nm) over four major cities of India using data from MODIS onboard the Terra and Aqua satellites

The paper evaluates long-term (2007–2018) temporal and spatial variations in aerosol optical depth (AOD) over four major cities of India, i.e., Delhi, Kolkata, Chennai, and Jaipur, by using Collection 6, Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua Level-3, 1°×1° gridded dataset. Annual analysis reveals a significant increasing trend from 2007 to 2018 and aerosol loading in the Indo-Gangetic Plain (IGP). Interestingly, in Northern India, i.e., Delhi, AOD values peaked during monsoon season (0.95–1.05), whereas over Kolkata, Eastern India, higher AOD is observed in winter season (0.95–1.05). Chennai, Southern India, reflects low to moderate mean AOD during all the seasons. A prominent increase in AOD percentage from 2007 to 2018 is observed over Kolkata (39%), followed by Delhi (27.34%), Chennai (26.30%), and Jaipur (16.53%). Further, cumulative effects of different meteorological parameters along with 12-year mean AOD reflected a peak in aerosol concentration (0.82 ± 0.06) over Delhi, closely followed by Kolkata (0.81 ± 0.08) and then Chennai (0.43 ± 0.03) and Jaipur (0.43 ± 0.03). Results depict a significant increase in AOD due to a wide range of anthropogenic events and call for improved policy programs to tackle the increasing AOD emissions over these megacities in India. © 2021, Saudi Society for Geosciences.