Summertime Turbulence Characteristics across China’ Planetary Boundary Layer: Roles of Wind Shear, Static Stability, Cloud and Topography-Land-Cover Conditions

Abstract. The spatio-temporal pattern of turbulence dissipation rate (ε) and its evolution remain elusive inside and above the planetary boundary layer (PBL). Using summertime 2022 data from a nationwide network of 132 radar wind profilers (RWPs), we contrast ε within the inner PBL (0.3 zᵢ ≤ z ≤ zᵢ) and above it (z ᵢ< z ≤ 3 zᵢ). Results reveal pronounced spatial heterogeneity: ε is strongest over Northwest and North China within the 30–40°N belt and weakest over the Tibetan Plateau and Southwest China, and it is systematically weaker aloft than within the PBL; ε also peaks near 1300 local time in both layers and persists day-to-day for roughly 9 days. We examine four modulating factors—topography and land cover, cloud conditions, static stability, and vertical wind shear (VWS). Of these, terrain complexity and land-cover type partly shape the observed heterogeneity, with stronger near-PBL turbulence over rough arid regions and weaker over water-dominated basins. Cloud cover enhances ε throughout the vertical column, with a stronger amplification above the PBL (△log₁₀ε = 0.16 m² s⁻³) than within it (0.1 m² s⁻³), mainly through intensified VWS. The dominant controls also differ with height: within the PBL, static stability and VWS jointly govern turbulence, whereas above the PBL turbulence is driven overwhelmingly by shear-generated disturbances. Spectral analysis further reveals distinct vertical stratification of turbulent energy density that strengthens under stronger VWS. These findings demonstrate the value of national RWP networks for resolving turbulent dynamics across China and provide observational constraints for PBL turbulence parameterization.