This study improves understanding of how complex urban surfaces modify turbulence and energy exchange within the urban boundary layer, enhancing sustainable city design. Turbulence statistics including Reynolds stress, normalized velocity standard deviations ( \(\:{{\upsigma\:}}_{\text{i}}/{\text{u}}_{\text{*}\text{l}}\) ), and turbulence intensity \(\:{{\upsigma\:}}_{\text{i}}/\stackrel{-}{\text{u}}\:,(\text{i}=\text{u},\text{v},\text{w})\) calculated at three levels (47, 120, and 280 m) under neutral and near-neutral conditions (April 10–20, 2020) and located on a 325-m tower in Beijing. The analysis investigates the accurate characterization of flow behavior within and above the roughness sublayer (RSL). Results show that within the RSL turbulence is highly variable and anisotropic, influencing by local roughness elements such as buildings and trees. Above the RSL, \(\:{{\upsigma\:}}_{\text{u},\text{v},\text{w}}/{\text{u}}_{\text{*}\text{l}}\) become nearly constant with height with values of 2.49, 2.25, and 1.51 respectively, indicating the development of a constant-flux layer. At higher levels of RSL, the dimensionless quantities \(\:{{\upsigma\:}}_{\text{u},\text{v},\text{w}}/\stackrel{-}{\text{u}}\) significantly decrease with height until become constants with values of 0.23, 0.21, and 0.16 respectively. The normalized Reynolds stress increases within the RSL and stabilizes above RSL with a value of about 4. All observation levels are located within a fully developed internal boundary layer, confirming complete urban flow adjustment. The results imply that urban climate and dispersion models should include the vertical transition to a post-urban boundary layer to better represent turbulence and surface–atmosphere exchanges in cities.
