A Semi-Spectral Numerical Model for Wave-Mean Flow Interactions in the Stratosphere: Application to Sudden Stratospheric Warmings

We describe a primitive equation model for numerical simulation of large-scale motions in the stratosphere. The model employs a finite-difference grid in the latitude-height plane. The longitudinal dependence is represented by the zonal mean plus a single Fourier wave component. A semi-implicit time differencing scheme is used. The model is used to study further the generation of sudden stratosphere warmings by wave-mean flow interaction as first described by Matsuno (1971). In general the results confirm Matsuno's model. However, the simulation for the planetary wavenumber 1 case does not exhibit the double-layer warming structure found by Matsuno, nor is there any evidence of a downward propagating critical level.