Technical note: Assessment of OMI/MLS Satellite-Derived Tropospheric Ozone Product for predicting monthly ground-level ozone concentrations

Abstract. Ground-level ozone is a hazardous air pollutant that contributes to respiratory and cardiovascular morbidity and mortality, as well as to climate change and vegetation damage. Despite its significance, global surface ozone monitoring remains spatially sparse, particularly outside of North America, Europe, and East Asia. Satellite-based products such as the Ozone Monitoring Instrument/Microwave Limb Sounder (OMI/MLS) tropospheric column ozone (TCO) dataset offer a potential solution for improving estimates of global ozone at ground level. Here we evaluate the performance of the OMI/MLS TCO product as a predictor of global ground-level ozone by comparing it to monthly average ground-based Maximum Daily 8-hour Average (MDA8) ozone measurements from the second Tropospheric Ozone Assessment Report (TOAR-II) database (2005–2022). Linear regressions were conducted globally, as well as by year, world region, concentration range, and month. A positive correlation was found between the TCO product and ground-based measurements, although that correlation was modest (R² = 0.29 over the entire period globally). Regression parameters did not vary strongly by season, region or year. Correlations were highest in May through October and highest in Europe and lowest in North America. The regression results were used with the satellite product to generate global maps of estimated ground-level ozone for each month from 2005 to 2022. While not a substitute for in situ measurements, our ground-level ozone product based on OMI/MLS TCO shows potential as an independent observational input to global data fusion methods in areas lacking ground-based monitoring.