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The annual assessment of emission control effects on air quality is essential for policy adjustments. However, this assessment is difficult as the inter‐annual changes in pollution are impacted by complex meteorological conditions. In this study, based on our wind‐pollution decomposition (WPD) method, which decomposes wind effects (wind‐driven) and nonwind effects, we established the meteorology‐pollution decomposition (MPD) method, which separates meteorological effects (met‐driven) and nonmeteorological effects by importing other meteorological parameters, to approximate the emission change effects (emission‐driven) by the nonmeteorological effects. The performance of the MPD method was assessed by comparing the results of the WPD and MPD methods at multiple representative stations in Hong Kong with the longest continuous data available in China from 2000 to 2018. The decomposed emission‐driven impact is also validated by using the gross domestic product growth rates data. The emission‐driven contributions determined by the WPD and MPD methods generally show agreement in trend, while the met‐driven effects are generally larger than the wind‐driven effects with the same or opposite trend. The results showed that the met‐driven effect from the MPD method is more reasonable than the wind‐driven effect from the WPD method in representing complex meteorological influences, which indicates a better representation of emission‐driven impacts by the nonmeteorological effects during the unusual meteorological years, such as El Niño‐Southern Oscillation events. The MPD method represents an independent approach, which is based only on regular observations, to quantify the long‐term trend in emission‐driven impacts as well as the integrated meteorological impacts on the atmospheric environment under the background of climate change. Key Points: A new method was proposed to separate the met‐driven and emission‐driven effects on observed inter‐annual air quality variationsBy incorporating factors other than wind, the new method better reflects the meteorological impacts in the background of climate changeThe emission‐driven effects of wind‐pollution decomposition and meteorology‐pollution decomposition generally show agreement in the long‐term trends, with larger differences in certain El Niño‐Southern Oscillation events [ABSTRACT FROM AUTHOR]

Although the effects of meteorological factors on severe air pollution have been extensively investigated, quantitative decomposition of the contributions of meteorology and anthropogenic factors remains a big challenge. The novel coronavirus disease 2019 (COVID-19) pandemic affords a unique opportunity to test decomposition method. Based on a wind decomposition method, this study outlined an improved method to differentiate complex meteorological and anthropogenic effects. The improved method was then applied to investigate the cause of unanticipated haze pollution in China during the COVID-19 lockdown period. Results from the wind decomposition method show that weakened winds increased PM 2.5 concentrations in the Beijing–Tianjin area and northeastern China (e.g., by 3.19 μg/m3 in Beijing). Using the improved decomposition method, we found that the combined meteorological effect (e.g., drastically elevated humidity levels and weakened airflow) substantially increased PM 2.5 concentrations in northern China: the most substantial increases were in the Beijing–Tianjin–Hebei region (e.g., by 26.79 μg/m3 in Beijing). On excluding the meteorological effects, PM 2.5 concentrations substantially decreased across China (e.g., by 21.84 μg/m3 in Beijing), evidencing that the strict restrictions on human activities indeed decreased PM 2.5 concentrations. The unfavorable meteorological conditions, however, overwhelmed the beneficial effects of emission reduction, causing the severe haze pollution. These results indicate that the integrated meteorological effects should be considered to differentiate the meteorological and anthropogenic effects on severe air pollution. • An improved method was outlined to assess meteorological effect on air pollution. • The cause of haze pollution during the COVID-19 lockdown period was investigated. • Elevated humidity and weakened airflow greatly increased PM 2.5 in northern China. • On excluding the meteorological effects, PM 2.5 substantially decreased across China. [ABSTRACT FROM AUTHOR]