Investigation of Low-Frequency Variability Using a Stochastic Atmosphere-Ocean Mixed Layer Model

Low frequency variability significantly influences weather and climate, and hence has important socio-economic impacts. The predictability of low-frequency variability has been a major challenge for the scientific community, and the mechanisms responsible for this variability remain unclear. In this talk, I discuss a new atmosphere-ocean stochastic model for understanding mechanisms of low-frequency variability. The atmospheric model is a linearized primitive equation model with nonlinear eddy-eddy interactions parameterized by stochastic forcing and augmented dissipation. The ocean model is a thermodynamic mixed layer model of constant depth. The resulting coupled model simulates realistic heat and eddy momentum fluxes of large-scale atmospheric eddies, despite the absence of orography, complex radiation, and convection. A simple parameterization of cloud-SST interaction is then included in the model and the changes in low-frequency variability are explored.