Abstract
The air pollution transmission channel in North China, also termed the ‘2 + 26’ cities, has the most severe pollution problem in China. Based on the meteorological and environmental observation data from 2014 to 2022, the spatial–temporal features of the air quality index (AQI) in the ‘2 + 26’ cities are first compared to reveal the different changes in winter and summer. Since the issue of the Air Pollution Prevention and Control Action Plan in China in 2013, the winter AQI averaged at the ‘2 + 26’ cities shows a significant decreasing trend of −9.725 μg m −3 per year from 2014 to 2022, but it shows much slight variation in summer. In summer, the ozone (O 3 ) pollutant is the major contributor to the AQI. Results indicate that higher T max and lower relative humidity (RH) are conducive to higher O 3 concentration and more severe air pollution. The averaged T max at these cities has a significant increasing trend of 0.28°C per decade, while RH decreases also significantly at a rate of −1.08% per decade. This may be the main reason why the summer O 3 concentration maintains stability at a high level in the recent 9 years. Results also indicate that the ‘heat dome’ effect, characterised by a persistent high pressure and warming air subsidence from the upper to lower troposphere, is reinforcing in recent years, and this is favourable for the occurrence of long‐lasting dry‐type high temperatures and the enhancement of O 3 pollution. Projections from 19 CMIP6 models show that the high pressure system will remarkably strengthen in the near, middle, and long terms under the moderate emission scenario (SSP2‐4.5). Therefore, the ‘heat dome’ effect will exacerbate the ozone pollution in the future.