Enhanced understanding of atmospheric blocking modulation on ozone dynamics within a high-resolution Earth system model

Abstract. High concentrations of surface ozone pose significant health risks, yet understanding the factors governing ozone levels, particularly the influence of large-scale circulations, remains incomplete. A key challenge lies in accurately modeling both large-scale circulations and ozone concentrations. Leveraging recent advancements in optimizing a high-resolution Earth system model with 25 km atmospheric resolution, how local meteorology and large-scale circulations impact ozone concentrations is investigated. We find that heatwaves can trigger substantial increases in ozone concentrations by stimulating biogenic volatile organic compound (BVOC) emissions during the summers of 2015–2019. For example, compared to non-heatwave periods, ozone concentrations during heatwaves increase by 12.0 ppbv in the southeastern U.S., 9.7 ppbv in Europe, 17.6 ppbv in North China, and 9.0 ppbv in central eastern China. In addition to local effects, atmospheric blocking strongly influences downstream meteorological conditions and ozone formation. Focusing on ozone pollution in eastern China, we identify three major pathways of Rossby wave propagation based on blocking locations: the Euro-Atlantic sector, northern Russia, and the North Pacific, inducing increased air temperature and intensified downward surface solar radiation downstream. The impact of blocking is most pronounced over central eastern China, where ozone concentrations during blocking increase by 5.9 ppbv to 10.7 ppbv compared to reference periods, followed by North China, ranging from 2.1 ppbv to 4.9 ppbv. Blocking can stimulate more BVOC emissions, enhancing ozone concentrations by 10.6 ppbv to 15.9 ppbv. These findings underscore the critical role that large-scale atmospheric circulation patterns play in regional-scale air quality, particularly under a warming climate.