TROPOMI NO2 in the United States: A Detailed Look at the Annual Averages,...
Observing the spatial heterogeneities of NO2 air pollution is an important first step in quantifying NOX emissions and exposures. This study investigates the capabilities of the Tropospheric Monitoring Instrument (TROPOMI) in observing the spatial and temporal patterns of NO2 pollution in the continental United States. The unprecedented sensitivity of the sensor can differentiate the finescale spatial heterogeneities in urban areas, such as emissions related to airport/shipping operations and high traffic, and the relatively small emission sources in rural areas, such as power plants and mining operations. We then examine NO2 columns by day-of-the-week and find that Saturday and Sunday concentrations are 16% and 24% lower respectively, than during weekdays. We also analyze the correlation of daily maximum 2-m temperatures and NO2 column amounts and find that NO2 is larger on the hottest days (>32°C) as compared to warm days (26°C–32°C), which is in contrast to a general decrease in NO2 with increasing temperature at moderate temperatures. Finally, we demonstrate that a linear regression fit of 2019 annual TROPOMI NO2 data to annual surface-level concentrations yields relatively strong correlation (R2 = 0.66). These new developments make TROPOMI NO2 satellite data advantageous for policymakers and public health officials, who request information at high spatial resolution and short timescales, in order to assess, devise, and evaluate regulations. Plain Language Summary Nitrogen oxides are a group of air pollutants released after fossil fuel combustion. A constituent of nitrogen oxides, nitrogen dioxide (NO2), can be observed by satellite instruments due to its chemical properties. In this project, we average together images of NO2 pollution gathered by the Tropospheric Monitoring Instrument satellite instrument over the United States in order to better determine the spatial distribution of NO2 air pollution. We find that this newest satellite instrument can observe air pollution with unprecedented clarity, similar to how HDTV is an advancement over regular TV. For example, we quantify pollution near individual airports, shipping areas, and major interstates; previous satellite instruments were unable to quantify air pollution with this type of precision. We also average the satellite data over different intervals to better determine cycles of air pollution. We find that NO2 air pollution is 16% lower on Saturdays and 24% lower on Sundays. Additionally, we find that NO2 pollution is larger on the hottest summer days as compared to typical summer days. These developments demonstrate how this new satellite instrument can advantageous for policymakers and health officials, who request information at high spatial resolution and short timescales, in order to assess, devise, and evaluate regulations