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Geostationary Air Quality Monitoring Substantiates Column NO2 as a Better O3 Formation Regime Indicator in China
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DOI:10.1029/2025JD045271.png)
Abstract
En 中文
China has become a global hotspot of ozone (O3) pollution, and understanding O3 formation regime is crucial for air quality management. Satellite-observed formaldehyde-to-nitrogen-dioxide ratio (HCHO/NO2, FNR) has long been demonstrated as an efficient way to infer O3 formation regime. However, reported FNR thresholds that divide O3 formation regimes into VOC-limited, transitional, and NOx-limited regimes uncover considerable differences. Using data from the world's first geostationary air quality monitoring instrument Geostationary Environment Monitoring Spectrometer, we report the spatiotemporal variations, particularly diurnal features, of O3-FNR relationships and O3 formation regimes in China. We find that O3-FNR relationships fluctuate significantly over time and across locations, with coefficients of variation (CVs) of 0.22 and 0.27, respectively. We identified the amount of HCHO as a key factor. Given the strong correlation between NO2 and LROx/LNOx (chemical loss of HO2+RO2 (LROx) to chemical loss of NOx (LNOx)), we demonstrate that O3 formation regime thresholds alter minimally when column NO2 is used as the indicator in China, with the CVs reduced to around 0.1. This finding highlights its potential to provide a more reliable diagnosis for large-scale, space-based O3 formation sensitivity, offering promising insights for advancing O3 pollution management in China.
Keywords:
Ozone formation regime
Formaldehyde-to-nitrogen-dioxide ratio
Geostationary remote sensing
Nitrogen dioxide
Air quality management
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