Comparison of Structure Parameter Scaling Expressions with Turbulence Closure Model Predictions

The convective boundary-layer scaling expressions presented by Wyngaard and LeMone (1980) are compared with predictions from a turbulence closure model. We first examine a model experiment involving a clear-air, convectively driven boundary layer overland. The model results agree well with scaling expressions and observations in the lower boundary layer and near the inversion. In the mid-boundary layer region, however, the closure model underestimates the temperature structure parameter CT2 and overestimates the humidity structure parameter Cq2. A cloud-topped marine boundary layer is examined in a second experiment which uses AMTEX data. Order-of-magnitude differences are found here between interfacial-layer scaling expressions and closure model predictions. Potential sources of this disagreement are discussed.