An alternative scaling for unsteady penetrative free convection

The daytime evolution of the atmospheric boundary layer under high pressure, anticyclonic synoptic systems over a homogeneous terrain can be successfully described by a penetrative free convection model, evolving from an initially stably stratified environment. In this article dimensional analysis has been employed to derive a new set of scaling parameters, which are functions of external, time-dependent, fluid properties and boundary conditions. This novel theoretical framework has been adopted to compare laboratory scale experiments, performed using a thermally controlled water tank and a Large Eddy Simulation (LES) numerical model. Both these have been developed for the characterization of the instabilities associated with the development of the Convective Boundary Layer (CBL). The characteristic length and time scales of the thermal plumes, their spatial distribution and interaction with the overlying stable layer are analyzed. The proposed scaling parameters appear to be representative of the bulk and turbulent properties of the CBL, as confirmed by both numerical and laboratory results.