Relationship between summer time near-surface ozone concentration and planetary boundary layer height in Beijing

• Published in: Atmospheric research 2023-09, Vol.293, p.106892, Article 106892
• Main Authors: Zhang, Chongzhao, Jiang, Zhongjing, Liu, Meijing, Dong, Yueming, Li, Jing
• Format: Article
• Language: English
• Subjects: Near-surface ozone; Planetary boundary layer height; WRF-Chem
• ISSN: 0169-8095; 1873-2895
• DOI: 10.1016/j.atmosres.2023.106892

The planetary boundary layer height (PBLH) is critical in affecting the concentration of air pollutants at surface. The relationship between PBLH and surface ozone concentration can be complicated but not entirely clear. In this study, by using observations and WRF-Chem simulations, we explore the relationship between the surface ozone and the PBLH in the summer daytime in Beijing, a major global ozone pollution hotspot. It is found that the surface ozone-PBLH relationship exhibits a three-stage evolution with ozone: first, increasing with PBLH, then keeping steady, and finally falling. The two turning points are around 1000 and 2000 m respectively. This process is likely controlled by the different contributions of chemical production and vertical mixing. Specifically, when PBLH is below ∼1000 m, as PBLH increases, chemical production increases owing to the light enhancement whereas the ozone contribution from vertical mixing remains weak due to the decreased ozone concentration gradient between the surface and the upper layer, resulting in a net gain of surface ozone concentration. When the PBL continues to rise, chemical production contributes less mainly due to the decrease of ozone precursors at the surface, whereas vertical mixing becomes more vigorous that further diluting surface ozone, resulting in a net loss of surface ozone concentration, especially when PBLH reaches above ∼2000 m. Our results contribute to understanding the variability of surface ozone in Beijing area and provide insights for local ozone air quality control. [Display omitted] •Surface ozone first increases with PBLH, then remains stable and finally decreases.•This relationship is jointly determined by vertical mixing and chemical processes.•Vertical mixing of ozone shifts from down to up when PBLH rises.•Chemistry contribution of ozone first increases then decreases when PBLH rises.