Low-frequency patterns induced by stationary waves

Abstract

A linear nine-level primitive equation model is used to determine whether the nonuniform geographical distribution of low-frequency variability and the underlying structure of low-frequency patterns can be attributed to inhomogeneities in the time-mean state of the atmosphere. The linear model's behaviour is compared with the low-frequency behaviour of a long simulation that has been performed with a general circulation model (GCM) whose numerical formulation matches that of the linear model. The variance of upper tropospheric streamfunction among 1000 steady linear responses to random distributions of thermal forcing is shown to be maximized in the same locations (particularly the North Pacific) as the low-frequency variance in the GCM. The principal low-frequency linear patterns primary source of energy is the conversion of basic state kinetic energy to perturbation kinetic energy. -from Author