Abstract
The long term variations of large-scale atmospheric motions were followed by a simple two-layer model with the nonadiabatic heating and cooling, and viscous dissipation. The computations were made by numerical procedures and partly by an analytical method in which the nonlinear feedback mechanism was taken into consideration.
Stability criterion of the growth or decay of the large-scale motion is derived by solving the frequency equation which is a quadratic form with respect to phase speed and with complex coefficients.
Kinetic energy spectrum of eddy meridional component was evaluated for the steady Rossby motion. The double maxima appeared in the spectral distribution. Then, the transient motion toward final equilibrium state is followed by numerical process, and the stability of the equilibrium state is examined by means of a variational equation. Time behaviours of the motion are largely characterized by a damping oscillation with well-defined periodicity. The period of oscillation varies widely from about ten days to a month.
Finally, conversions between various types of energies, and energy flow diagram are obtained and compared with the results of weather map analyses and numerical experiments. Fairly good coincidences are seen in the direction of energy flow and also magnitude of energy conversions.
