Himalaya air quality impacts from the COVID-19 lockdown across the Indo-Gangetic Plain

Abstract:

Starting in January 2020, the novel coronavirus, now known as acute respiratory syndrome coronavirus (SARS-CoV-2) and the disease that it causes (COVID-19) has had significant impacts on human health, the environment and the economy globally. The rapid lockdown that occurred as well as its well documented timing in various locations allows for an unprecedented opportunity to examine the impact of air pollution from densely populated regions has on adjacent and pristine environments. Here we use in-situ and satellite observations to show that there was a step function decrease in two key indicators of air quality, nitrogen dioxide and airborne particulates, in locations within the Indo-Gangetic Plan (IGP) as a result of the lockdown. We find a dipolar response with a statistically significant reduction in air pollution along the western Himalaya and an increase in air pollution in the eastern Himalaya. We show that spatial variability in the reductions in economic activity across northern India and the adjoining countries of Nepal, Pakistan and Bangladesh contributed to this dipole as did a persistent atmospheric circulation anomaly across the region during April 2020.