These images, using data from the Copernicus Sentinel-5P satellite, show the average nitrogen dioxide concentrations from 25 March to 20 April 2019 and average concentrations from 25 March to 20 April 2020. The spikes in the top image show concentrations from 2019 over Delhi and Mumbai. Owing to COVID-19 restrictions, the 2020 image shows high concentrations in northeast India, which coincides with the ongoing activity in coal-based power plants in east India.
A trail of nitrogen dioxide emissions from maritime traffic can be seen as a faint line over the Indian Ocean (visible in the bottom of the image.) Shipping lanes appear as straight lines owing to commercial ships following more or less the same route.
The concentrations of nitrogen dioxide in our atmosphere vary widely on a daily basis. Variations owing to weather conditions make it necessary to average data over substantial periods of time – allowing for more accurate assessments to be made.