Frequently strong boundary-layer vertical wind shear dominates heavy air pollution over the typical deep basin

• Published in: Atmospheric research Vol. 327; p. 108337
• Main Authors: Zhao, Suping, Yu, Ye, He, Jianjun, Zhang, Tong, Dong, Longxiang, Zhang, Xiaoling, Qi, Shaofeng
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2026
• Subjects: Air pollution; Complex terrain; Deep basin; Planetary boundary layer; Vertical wind shear; Air pollution; Vertical wind shear; Deep basin; Complex terrain; Planetary boundary layer
• ISSN: 0169-8095
• DOI: 10.1016/j.atmosres.2025.108337

Vertical wind shear frequently occurs in complex terrain (basin and sloped terrain). However, compared with thermodynamic (temperature inversion) variables, the modulation of dynamic (wind shear) variables on air pollution is poorly understood due to scarce in-situ observations at complex terrain. In order to reveal the issues, we conducted the first collaborative field experiment of Boundary-Layer Meteorology and Pollution at western Sichuan Basin (BLMP-SCB) at a rural site from December 2018 to January 2019. A clockwise turning of the wind with the height was more frequent, especially for the rotation smaller than 20 degrees, which corresponded to the heavy air pollution near the ground surface. The surface heavy air pollution was jointly influenced by both low-level wind-directional shear and speed shear above that layer, especially the configuration of southeasterly winds below 1.0 km above sea level (regional transport) and increased southwesterly winds with height above the height (subsidence motion). The elevated wind-directional shear enhanced mechanical turbulence to transport downwards secondary pollutants to upper atmospheric boundary layer from the higher layer of air. The increased wind speed with height more easily triggered subsidence motion to trap more pollutants inside the basin. The work was helpful for fully understanding the role of meteorological variables in the formation and development of heavy air pollution at complex terrain, which will be favorable for making targeted pollution prevention and control measures at complex terrain. [Display omitted] •A clockwise turning of the wind with the height was more frequent, corresponding to heavy pollution.•The surface heavy pollution was jointly influenced by low-level WDS and WSS.•Elevated wind-directional shear enhanced turbulence to transport downwards secondary pollutants.•WSS more easily triggered subsidence motion to trap more pollutants inside the basin.