Monitoring Nitrogen Dioxide during COVID-19 in over 300 Cities Using OMI Satellite Data

Nitrogen oxides (NOx = NO + NO2) emissions are primarily emitted through the combustion of fossil fuels, such as automobiles and power plants. NOx can contribute to chemical reactions that produce ozone and particulate matter (PM2.5) pollution making it difficult to breathe. Satellite measured NO2 vertical column density (VCD) can act as an indicator of the amount of NOx pollution on global scale. Using NO2 data from satellite hyperspectral instruments, such as the Ozone Monitoring Instrument (OMI) on board NASAs EOS Aura satellite, one can monitor changes in NO2 columns during black-swan events, such as mobility restrictions during COVID-19 lockdowns. Our OMI NO2 team has created the Global Nitrogen Dioxide Monitoring Home Page (https://so2.gsfc.nasa.gov/no2/no2_index.html ) where we display NO2 column changes compared to a pre-COVID five-year average for 311 cities around the world. During the pandemic as a result of the widespread lockdowns, many areas saw NO2 that was lower than the pre-COVID five-year average. We also observe non-COVID related positive and negative NO2 changes due to seasonal and daily changes in weather. The data are displayed in several ways. First the world map shows the locations of cities color-coded changes by OMI-observed NO2 changes. Clicking on a city symbol brings up a time series plot showing a 15-day running median, mean and NO2 anomaly, as well as a movie showing the changes around the city. We also make these data available in a downloadable text file. To get a bigger picture, these data are also shown on a regional to continental scales. These regional maps show the current values of NO2 as well as the differences from the pre-COVID five-year average in a movie format. We will present case studies using visualizations from the web site to show how the COVID-19 pandemic affected changes in NO2 largely due to changes in human behavior.