Feasibility of robust estimates of ozone production rates using satellite observations

Abstract. Ozone pollution is secondarily produced through a complex, non-linear chemical process. Our understanding of the spatiotemporal variations in photochemically produced ozone (i.e., PO₃) is limited to sparse aircraft campaigns and chemical transport models, which often carry significant biases. Hence, we present a novel satellite-derived PO₃ product informed by bias-corrected TROPOMI HCHO, NO₂, surface albedo data, and various models. These data are integrated into a parameterization that relies on HCHO, NO₂, HCHO/NO₂, jNO₂, and jO¹D. Despite its simplicity, it can reproduce ~90 % of the variance in observationally constrained PO₃ with minimal biases in moderately to highly polluted regions. We map PO₃ across various regions in July 2019 at a 0.1°×0.1° spatial resolution, revealing accelerated values (>8 ppbv/hr) in numerous cities throughout Asia and the Middle East, resulting from the elevated ozone precursors and enhanced photochemistry. In Europe and the United States, such high levels are only detected over Benelux, Los Angeles, and New York City. PO₃ maxima are seen in various seasons, attributed to changes in photolysis rates, non-linear ozone chemistry, and fluctuations in HCHO and NO₂. Satellite errors result in moderate errors (40–60 %) of PO₃ estimates over cities on a monthly average, while these errors exceed 100 % in clean areas and under low light conditions. Using the current algorithm, we have demonstrated that satellite data can provide valuable information for robust PO₃ estimation. This capability expands future research through the application of data to address significant scientific questions about the locally-produced PO₃ hotspots, seasonality, and long-term trends.