Modeling of spatial and temporal variations of ozone-NOX -VOC sensitivity based on photochemical indicators in China

Comprehensive air quality model with extensions (CAMx)-decoupled direct method (DDM) was used to simulate ozone-NO x -VOCs sensitivity of for May???November in 2016???2018 in China. Based on the relationship between the simulated ozone (O 3 ) sensitivity values and the ratio of formaldehyde (HCHO) to NO 2 (FNR) and the ratio of production rate of hydrogen peroxide (H 2 O 2 ) to production rate of nitric acid (HNO 3 ) ( P H 2 O 2 /P HN O 3 ), the localized range of FNR and P H 2 O 2 /P HN O 3 thresholds in different regions in China were obtained. The overall simulated FNR values are about 1.640???2.520, and P H 2 O 2 /P HN O 3 values are about 0.540???0.830 for the transition regime. Model simulated O 3 sensitivities or region specific FNR or P H 2 O 2 /P HN O 3 thresholds should be applied to ensure the accurate local O 3 sensitivity regimes. Using the tropospheric column FNR values from ozone monitoring instrument (OMI) satellite data as an indicator with the simulated threshold values, the spatial distributions of O 3 formation regimes in China are determined. The O 3 sensitivity regimes from eastern to central China are gradually from VOC-limited, transition to NO x -limited spatially, and moving toward to transition or NO x -limited regime from 2005 to 2019 temporally. ?? 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.