A SALINE LABORATORY MODEL OF THE PLANETARY CONVECTIVE BOUNDARY-LAYER

A laboratory water-analog of clear-air penetrative convection in the a tmosphere has been constructed to continue studies of the turbulent di spersion of buoyant plumes in the convective boundary layer (CBL). A u nique feature is the utilization of saline rather than thermal convect ion, which has been made possible by the development of a reliable met hod for delivering a controllable buoyancy flux through a porous membr ane. It has been shown in an earlier paper that at typical laboratory scales, a saline convection tank is well suited to modelling buoyant p lume dispersion under strongly convective (light wind) conditions. A r ange of experiments has clearly demonstrated the validity of the model . Results for density and velocity variances show much less scatter th an most comparable measurements because of the greatly improved sampli ng that is possible in the tank. The results are generally in good agr eement with field data and other laboratory simulations but the improv ed accuracy of the data has highlighted the anomalously low values for the horizontal velocity variances produced by large-eddy simulations of the CBL. The cause of this apparent underprediction remains unresol ved.