DIAGNOSTIC TESTS OF MODELS FOR THE THERMAL STRUCTURE OF THE NON-PRECIPITATING CONVECTIVE BOUNDARY LAYER

This paper presents a diagnostic study of two models proposed by Betts (1973a). The first was a model for a well mixed sub-cloud layer capped by a more stable transition layer Csee Fig. 2.1). The downward heat flux at the base of this transition layer is here estimated from the thermal structure of the layer to be 15-25% of the surface sensible heat flux.

The second model was a model for a two layer lapse-rate structure for the cumulus layer. A sensitivity analysis is conducted on this lapse—rate model. The model results compare favorably with observational evidence from the BOMEX, ATEX and VIMHEX tropical field experiments. The parameterization of entrainment is examined through model calculations, and by radiosonde ascents into cloud. It is found that the scaling of entrainment by the depth of the layer of conditional instability (as used in the model) is satisfactory; but that other depths of the cloud layer could be used equally well.

Related Topics

• Boundary Layer,
• Convection,
• Datasets,
• Idealized models,
• Parameterization,
• Thermodynamics,
• VIMHEX