Residual layer effects on the modeling of convective boundary layer growth rates with a slab model using FIFE data

The ability of slab models for the growth of the convective boundary layer (CBL) to work in the presence of residual layers above is analyzed in detail with a large data set from the First International Satellite Land Surface Climatology Project Field Experiment (FIFE)-87 and FIFE-89 experiments. We confirm that the critical element that allows the models to predict the growth as the CBL coalesces with the residual layer is the adoption of a variable lapse rate above the growing CBL. This is not a new finding per se, as several previous studies in the literature have adopted this strategy. Different parameterizations of a slab model, based on the turbulence kinetic energy budget at the top of the CBL, were tested, and the inclusion of the storage and dissipation terms did not improve the model. Among the alternatives for choosing the lapse rate as the CBL grows, fair results are obtained with a simple choice of two values, with absolute mean errors of the order of 270 m for cases with and without a residual layer. Both lapse rates, representative of the residual layer and the free atmosphere, are obtained from the first morning sounding. Finally, an alternative model for the CBL growth into a residual layer that assumes a zero-lapse rate above the CBL did not perform well with the FIFE data.