Effects of atmospheric stability on air flow and pollutant dispersion characteristics within different scale urban areas.

This article focuses on investigating the multiscale characteristics of airflow, heat transfer, and pollutant dispersion in urban areas under varying atmospheric stability conditions, characterized by the bulk Richardson number (Ri_b). Using a validated numerical model spanning neighborhood to indoor scales and two building array types—aligned (AL) and staggered (ST)—the study finds that pollutant dispersion and dilution are significantly reduced under stable atmospheric conditions and AL arrays, while unstable conditions enhance ventilation efficiency up to a critical Ri_b threshold. The ST array consistently demonstrates better ventilation performance and pollutant dilution than the AL array, although it may increase the longitudinal diffusion range of pollutants. These findings highlight the combined influence of atmospheric stability, building layout, and pollutant source location on urban air quality and ventilation across multiple spatial scales.