Ocean-atmosphere interactions and climate drift in a coupled general circulation model

We have analysed numerical simulations performed with a global 3D coupled a tmosphere-ocean model to focus on the role of atmospheric processes leading to sea surface temperature (SST) drift in the tropics. Negative SST errors occur coherently in space and time with large positive errors in latent he at and momentum fluxes at the tropical air-sea interface, as diagnosed from forced SST simulations. The warm pool in the western Pacific disappears af ter a few years of simulation. Strong SST gradients enforce regions of high precipitation that are thin and stationary north of the equator. We detail the implications for the ocean-atmosphere system of such upheaval in the d eep convection location. A sensitivity experiment to empirically formulate air-sea drag coefficient shows that the rapid warm pool erosion is not sens itive to changes in the formulation of the surface drag coefficient over th e oceans because the corresponding changes in turbulent heat fluxes and LW cooling approximately cancel one another. In the eastern Pacific, the impro vement ill SST is striking and caused by feedbacks between SST, surface tur bulent fluxes and boundary layer cloud fraction, which decreases as SST war ms.