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The ongoing COVID-19 pandemic necessitated a complete lockdown from 24 March to 31 May 2020 as imposed by the Government of India to prevent the spread of the virus that resulted into halting most of the economic activities during that period. The stringent anthropogenic activities during the lockdown phase resulted in a notable drop in the air pollution level. The prevailing global scenario during the pandemic has provided an opportunity of assessing the air quality in the absence of normal anthropogenic activities. In the present article, the impacts of reduced anthropogenic activities on the black carbon concentration and associated atmospheric parameters have been studied over a tropical urban location, Kolkata (22.57°N, 88.37°E) in eastern India. Investigations have been made on the impacts on the parameters like atmospheric electric field, wind speed, temperature, relative humidity, dew point temperature, rain accumulation and soil moisture during this unusual time in comparison to the same time span of the previous year 2019 when the usual human activities were pursued. [ABSTRACT FROM AUTHOR]

Near surface aerosol black carbon (BC) concentration data were collected using a seven channel Aethalometer (AE31) during June 2012–May 2013 in Kolkata (22° 34′E, 88° 22′N), a metropolitan city located near the land–ocean boundary in Eastern India. BC concentration shows a prominent seasonal and diurnal variation associated with the meteorological parameters. The mean BC concentration varied from 5 μg/m 3 to 27 μg/m 3 seasonally. The variation of BC mass concentration and its significant association with atmospheric parameters such as temperature profile, relative humidity and wind speed have been studied. Moreover, the influence of the transported air masses on BC concentration at different seasons has also been discussed. An estimation of Angstrom exponent discloses that fossil fuel combustion is a major source of BC at this location. [ABSTRACT FROM AUTHOR]

Continuous measurements of Aerosol Optical Depth (AOD), columnar water vapor (WV) and Ozone (O 3) concentrations were made over a semi-arid urban location Rajkot (22.29°N, 70.74°E, and 142 m AMSL) in the western India. The annual mean values of AOD, WV and O 3 were 0.37 ± 0.15, 1.44 ± 0.6 gm cm−2 and 243 ± 18 DU during 2016–2019. AOD showed large seasonal variability mostly dominated by abundant coarse mode aerosols (Angstrom Exponent, AE < 0.65 and AOD ∼ 0.37) during pre-monsoon and monsoon, mainly caused by wind-blown and transported dust from nearby Thar and Kutch desert. Mixture of fine and coarse mode aerosols were abundant (AE = 1.13 ± 0.26) during post-monsoon influenced by both anthropogenic and natural sources. Columnar WV were also higher in pre-monsoon and monsoon seasons. The O 3 concentrations is higher during pre-monsoon (247 DU) and lower during monsoon (230 DU). The vertical distribution of aerosol extinction coefficient derived from satellite (CALIPSO) based observations revealed the dominance of dust aerosols (∼74 %) in pre-monsoon; smoke and polluted dust in winter and post monsoon period. The trajectory clusters and concentration weighted trajectory maps also indicated the combined effect of anthropogenic (especially from the northern part of India) and natural aerosol sources during the post-monsoon period. Associated with the higher anthropogenic components during post-monsoon season, aerosol direct radiative forcing depicted surface dimming as high as − 48.7 ± 12.6 Wm−2, resulting in atmospheric forcing of 42.6 ± 12.5 Wm−2. [ABSTRACT FROM AUTHOR]

Atmospheric pollutants (NO 2 , SO 2 , PM10, BC, CO, surface O 3 ), emitted during fireworks display, have significant effects on meteorological parameters like air temperature, relative humidity, lapse rate and visibility in air over Kolkata (22°65′ N, 88°45′ E), a metropolitan city near the land–ocean boundary, on the eve of Deepawali festival when extensive fireworks are burnt. Long-term trend (2005–2013), indicates that the yearly average concentrations of both primary and secondary air pollutants have increased, exceeding the National Ambient Air Quality Standard (NAAQS) limit, on the respective Deepawali days. Short-term study (2012–2013) during the festival shows that the average pollutant concentrations have increased too compared to normal days. This study also reveals the immediate effects of the increased air pollutants on the boundary layer meteorology. PM10 has been found to be the most dominant atmospheric pollutants during this period. As a result of an increase in atmospheric heat content with elevated surface air temperature, a significant increase in the environmental lapse rate bears a signature of the influence of pollutants on the boundary layer temperature profile. A change in the diurnal pattern of relative humidity as well as in the vertical temperature profile is due to the change of the lapse rate during the festival days. Thus, the atmospheric pollutants during this festival over the urban region have significant effect on the boundary layer meteorology with bearings on environmental hazards. [ABSTRACT FROM AUTHOR]