Elucidating diurnal variability of ozone sensitivity and driving factors in Asia with the world’s first geostationary air pollution satellite

Tropospheric ozone (O3) is a major air pollutant, which not only exerts detrimental effects on human health and ecosystem productivity and but also controls atmospheric oxidizing capacity. Besides, it is the third potent climate forcer that interacts with both solar and terrestrial radiation. Asian countries, particularly China, are facing the pressing challenge of increasing O3 pollution. Tropospheric O3 is formed from photochemical oxidation of volatile organic compounds (VOCs) in the presence of nitrogen oxides (NOx), and understanding O3-NOx-VOCs sensitivity plays a crucial role in designing effective O3 pollution control strategies. Here we aim to elucidate spatiotemporal, particularly diurnal, variability of O3 sensitivity in Asia using the world’s first geostationary air pollution satellite, with discussions on drivers for spatiotemporal heterogeneity. A new indicator that varies less with time and space will be proposed to better diagnose O3 sensitivity over a large geographic area like Asia.

O3 sensitivity inferred from chemical transport models or ground-based observations have the limitations of large uncertainties or limited spatial coverage. Although polar-orbiting satellites have been widely to explore O3 sensitivity over extended time periods and on a large spatial scale, its diurnal variability remains unclear and FNR thresholds that decided O3 formation regimes varied greatly across different studies. In this project, we propose to combine our expertise in remote sensing of air pollution and atmospheric chemistry modeling, and to use the world’s first geostationary air pollution satellite, the Geostationary Environment Monitoring Spectrometer (GEMS), to elucidate the spatiotemporal including diurnal variability of O3 sensitivity and the underlying causes in Asia. We will analyze GEMS satellite retrievals of formaldehyde (HCHO) and nitrogen dioxides (NO2) and ground-based measurements of O3 concentrations to obtain the FNR values to decide O3 formation regimes. Accordingly, the spatiotemporal particularly diurnal variability of O3 sensitivity will be offered, and we will then explore how environmental affect the identified variability using both statistical analysis and numerical box modeling. We will also propose a new indicator to include these environmental factors and achieve a better diagnosis of O3 sensitivity with less differences over a large geographic area, which can be more easily adopted in future studies.

This project will be the first demonstration of geostationary satellite in monitoring O3 sensitivity and will offer unprecedented implications for O3 pollution control over Asia. The results have the potential to benefit public health or ecology communities as well.