Detectability assessment of a satellite sensor for lower tropospheric ozone responses to its precursors emission...

Satellite sensors are powerful tools to monitor the spatiotemporal variations of air pollutants in large scales, but it has been challenging to detect surface O₃ due to the presence of abundant stratospheric and upper tropospheric O₃. East Asia is one of the most polluted regions in the world, but anthropogenic emissions such as NO_x and SO₂ began to decrease in 2010s. This trend was well observed by satellites, but the spatiotemporal impacts of these emission trends on O₃ have not been well understood. Recent advancement in a retrieval method for the Ozone Monitoring Instrument (OMI) sensor enabled detection of lower tropospheric O₃ and its legitimacy has been validated. In this study, we investigated the statistical significance for the OMI sensor to detect the lower tropospheric O₃ responses to the future emission reduction of the O₃ precursor gases over East Asia in summer, by utilizing a regional chemistry model. The emission reduction of 10, 25, 50, and 90% resulted in 4.4, 11, 23, and 53% decrease of the areal and monthly mean daytime simulated satellite-detectable O₃ (ΔO₃), respectively. The fractions of significant areas are 55, 84, 93, and 96% at a one-sided 95% confidence interval. Because of the recent advancement of satellite sensor technologies (e.g., TROPOMI), study on tropospheric photochemistry will be rapidly advanced in the near future. The current study proved the usefulness of such satellite analyses on the lower tropospheric O₃ and its perturbations due to the precursor gas emission controls.