Satellite Detection of NO₂ Distributions and Comparison with Ground-Based Concentrations

Abstract. In this study we assess the capability of current-generation satellites to capture the variability of near-surface nitrogen dioxide (NO₂) monitoring data, with the goal of supporting health and regulatory applications. We consider NO₂ vertical column densities (VCD) over the United States from two satellite instruments, the Tropospheric Monitoring Instrument (TROPOMI), and Tropospheric Emissions: Monitoring of Pollution (TEMPO), and compare with ground-based concentrations as measured by the EPA’s Air Quality System (AQS) monitors. While TROPOMI provides a longer-term record of assessment (2019–2023), TEMPO informs diurnal patterns relevant to evaluating peak NO₂. We analyze frequency distributions and quantify their similarity using the Jensen-Shannon Divergence (JSD), where smaller values indicate better agreement. Satellite and ground monitor NO₂ distributions are most similar away from major roads, as indicated by the JSD of 0.008 calculated for TROPOMI and ground monitors at non-roadways, compared with a JSD near interstates of 0.158 and a JSD near highways of 0.095. Seasonal analysis shows the most similarity in distributions in winter, with a JSD of 0.010, and the most difference in summer, with a JSD of 0.035. Across seasons and monitor locations, TEMPO consistently has a lower or similar JSD as TROPOMI, with TEMPO JSDs ranging from 0.005 to 0.151 and TROPOMI JSDs ranging from 0.012 to 0.265. TEMPO’s agreement with monitors in both December 2023 and July 2024 is found to be best around midday, with non-road monitors’ JSD in July as low as 0.008 at 16 UTC (~11 am LT).