Surprising increase in aerosol amid widespread decline in pollution over India during the COVID19 Lockdown

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Satyndera Kumar Pandey , Vinoj V


Using ground-based and satellite observation along with aerosol reanalysis products, we show a widespread reduction in aerosol loading over the Indian subcontinent during the COVID19 lockdown. In terms of aerosol optical depth (AOD), loading has reduced up to 40 % over the most populated region of India. However, the central part of India shows an unexpected increase (~+20 %) in aerosol optical depth. Using meteorological reanalysis data, it is shown that a simultaneous increase (decrease) in mid-tropospheric relative humidity (wind speed (WS) at 850 hPa) by +85±6.0 % (-12±3.9 %) occurred during the lockdown. It is found that on a daily scale, the mean AOD is positively (negatively) correlated, with mid-tropospheric RH (WS) with a statistically significant linear correlation coefficient 0.53 (-0.43). An increase (decrease) in RH (WS) of 20 % (1 ms-1) was observed to increase AOD by 0.10 (0.04). Thus we hypothesize that during the lockdown, the increased AOD over central India was due to increased atmospheric moisture coupled with stagnant circulation condition. Also, aqueous-phase chemistry may have played a role by enhancing new particle formation.



Atmospheric Sciences, Climate, Environmental Indicators and Impact Assessment, Environmental Monitoring, Environmental Sciences, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics



Published: 2020-07-06 08:50

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