Spatiotemporal Variability and Associated Environmental Factors of Tropospheric NO2 Column Density over North China from TROPOMI Observations, 2019–2023

With the sustained industrial development, air pollution remains a prominent environmental challenge in North China. As a key atmospheric contaminant, nitrogen dioxide (NO2) is closely associated with significant adverse impacts on both ecological systems and public health. However, existing research regarding the factors related to NO2 column concentration and the comparative strength of these associations remains limited. To address this research gap, this study employs TROPOMI satellite-based NO2 data and six categories of influencing factors (meteorology, population density, vegetation coverage, etc.) to characterize the spatiotemporal patterns and the statistical relationships between NO2 column concentrations and various influencing factors in North China from 2019 to 2023. The results indicate that elevated NO2 column concentrations are primarily concentrated in central North China, including northern Henan, southern Hebei, and central–western Shandong. During 2019–2023, the regional NO2 column concentration displayed an overall decreasing trend, accompanied by distinct seasonal variations: peaking in winter, moderate in autumn, and reaching the minimum in summer. Among the evaluated factors, temperature exhibited the strongest correlation with NO2 variations, followed by surface net solar radiation and Normalized Difference Vegetation Index (NDVI). The relationship between wind and NO2 was found to vary according to direction, speed, and regional topography. In addition, population density showed a prominent positive association with NO2 vertical column density. This study identifies key factors linked to NO2 variability, thereby providing methodological and empirical support for relevant studies in other regions.