Sensitivity of Climate Drift to Atmospheric Physical Parameterizations in a Coupled Ocean–Atmosphere General Circulation Model

Abstract

Sensitivity of climate drift to selected convection and cloudiness parameters is investigated with a coupled ocean?atmosphere general circulation model. The dependence of the coupled model climatology upon parameterizations of convective entrainment and stratocumulus cloud cover is studied. The methodology relies upon short uncoupled (1 yr) and coupled (3 yr) simulations. The coupled model climatology is very sensitive to both parameterizations. For instance, the air?sea interface mean state can be too warm or too cold depending on the profile of the convective entrainment rate. Enhanced entrainment at lower levels breaks the symmetry of the tropical precipitation pattern observed in both forced and coupled control simulations. Furthermore, the zonal wind stress strength and related thermocline slope around 150°W are shown to be crucial in determining the warm pool?cold tongue structure in the tropical Pacific. The model sensitivity is found to be the result of complex feedbacks between convection, cloud, and boundary layer processes, sea surface temperature (SST), and large-scale ocean?atmosphere dynamics.