A Model of the Thermodynamic Structure of the Trade-Wind Boundary Layer: Part II. Applications

Abstract

Several applications of a simple layered model of the temperature and moisture structure of the trade-wind boundary layer are considered. The formation of the trade inversion in the wake of disturbed conditions is simulated. This simulation indicates that the observed thermodynamic structure can easily evolve from a shallow mixed layer in less than 24 h. The growth rate of the depth of the boundary layer is shown to be most sensitive to parameters which directly influence the surface fluxes of heat and moisture. Steady-state model results are compared to the boundary-layer structure observed during the 1969 Atlantic Trade-Wind Experiment (ATEX). The predicted structure is slightly warmer and more moist than the observed structure. These differences are largely eliminated if the variation of the model structure following a surface air trajectory is predicted. The effect of a diurnally varying radiative heating and divergence on the height of the inversion is evaluated. These model results are compared to diurnal variations in the height of the inversion observed from the ship Meteor during ATEX. The model is also used to simulate the thermodynamic structure when the cloud layer becomes saturated. The steady-state and time-dependent results of this simulation are in very good agreement with the results obtained with a cloud-topped mixed-layer model.