SENSITIVITY OF CLIMATE DRIFT TO ATMOSPHERIC PHYSICAL PARAMETERIZATIONS IN A COUPLED OCEAN-ATMOSPHERE GENERAL-CIRCULATION MODEL

Sensitivity of climate drift to selected convection and cloudiness par ameters is investigated with a coupled ocean-atmosphere general circul ation model. The dependence of the coupled model climatology upon para meterizations of convective entrainment and stratocumulus cloud cover is studied. The methodology relies upon short uncoupled (1 yr) and cou pled (3 yr) simulations. The coupled model climatology is very sensiti ve to both parameterizations. For instance, the air-sea interface mean state can be too warm or too cold depending on the profile of the con vective entrainment rate. Enhanced entrainment at lower levels breaks the symmetry of the tropical precipitation pattern observed in both fo rced and coupled control simulations. Furthermore, the zonal wind stre ss strength and related thermocline slope around 150 degrees W are sho wn 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 pr ocesses, sea surface temperature (SST), and large scale ocean-atmosphe re dynamics.