Field Observations Validate LES‐Derived Scaling of Vertical‐Velocity Variance During the Afternoon Transition of the Convective Boundary Layer

Abstract The convective velocity scale is commonly used to describe the vertical‐velocity variance in the convective boundary layer driven by surface heating, and is valid when the surface heat flux varies slowly compared to the eddy turnover time. This quasi‐equilibrium assumption typically holds from late morning to early afternoon, but breaks down in the late afternoon. Recent idealized large‐eddy simulations (LES) of free convection reported departure from the classical convective scaling due to quasi‐equilibrium breakdown, and identified the relevant parameters to describe the vertical‐velocity variance during the late afternoon transition. In this study, we evaluate these scaling predictions using extensive field observations spanning 264 days. Despite substantial day‐to‐day variability, averaging across multiple days reveals a good agreement between observations and the LES‐derived scaling, supporting its validity for describing vertical‐velocity variance in this regime.