ABSTRACT
The government of India imposed a nationwide lockdown to tackle the outbreak of COVID-19 in 2020. This period witnessed record low anthropogenic activity, which had severe socio-economic impacts but also had orthogonal effects on the ambient air quality of the atmosphere. This study focuses on the variations in the atmospheric boundary layer (ABL) over a western Indian urban region in the light of COVID-19. Continuous backscatter recorded by a ceilometer, stationed at Ahmedabad, was used in this study to monitor the ABL during the national lockdown (NLD) in 2020 and state restrictions in 2021, and compared with the control year of 2019. In parallel, improvement in air quality during the NLD was observed by the SAFAR air quality station at Ahmedabad, with decreased particulate matter concentrations. The ground-based observations were substantiated by the ERA5 reanalysis dataset. A decline in the ABL height was recorded during the NLD, which showed improvement in 2021 but which was shy of the ABL in 2019. This was correlated with rain events during the observational period, recorded by an automatic weather station.
ABSTRACT
Black carbon (BC) aerosols critically impact the climate and hydrological cycle. The impact of anthropogenic emissions and coastal meteorology on BC dynamics, however, remains unclear over tropical India, a globally identified hotspot. In this regard, we have performed in situ measurements of BC over a megacity (Chennai, 12° 59' 26.5â³ N, 80° 13' 51.8â³ E) on the eastern coast of India during January-June 2020, comprising the period of COVID-19-induced strict lockdown. Our measurements revealed an unprecedented reduction in BC concentration by an order of magnitude as reported by other studies for various other pollutants. This was despite having stronger precipitation during pre-lockdown and lesser precipitation washout during the lockdown. Our analyses, taking mesoscale dynamics into account, unravels stronger BC depletion in the continental air than marine air. Additionally, the BC source regime also shifted from a fossil-fuel dominance to a biomass burning dominance as a result of lockdown, indicating relative reduction in fossil fuel combustion. Considering the rarity of such a low concentration of BC in a tropical megacity environment, our observations and findings under near-natural or background levels of BC may be invaluable to validate model simulations dealing with BC dynamics and its climatic impacts in the Anthropocene.
Subject(s)
Air Pollutants , COVID-19 , Humans , Air Pollutants/analysis , Meteorology , India , Communicable Disease Control , Respiratory Aerosols and Droplets , Fossil Fuels/analysis , Carbon/analysis , Environmental MonitoringABSTRACT
The present study investigates the association of COVID-19 virus transmission with atmospheric and air quality parameters including temperature, moisture, particulate matter (PM), and nitrogen dioxide (NO2). The variation in the reproduction number (R 0; a measure to reflect the infectiousness of a disease) for COVID-19 transmission is evaluated for tropical and mid-latitude countries. Results suggest that mid-latitude atmospheric conditions are more favorable to COVID-19 transmission as compared to the tropical atmosphere. The peak value of R 0 was noted as 2.35 (95% CI 2.11-2.57) on 23 March 2020, and it decreased significantly due to strict lockdown from 25 March 2020 to 1 April 2020. The R 0 value further increased after 1 April 2020 over India, and the value of R 0 was found to be greater than 1, indicating that the epidemic was active. Moreover, the present study was also extended to understand the impact of global/Indian lockdowns on air quality and R 0 value for COVID-19 transmission. Our findings revealed that the global/Indian lockdown helped reduce the R 0 value of COVID-19 transmission, which is associated with atmospheric and air quality parameters. Furthermore, a significant reduction in air pollution over India during the lockdown also has implications for continued exploration of clean energy prospects in the future. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00024-021-02793-0.