Air Parcel Motions during a Numerically Simulated Sudden Stratospheric Warming

The three-dimensional mass motions in a mechanistic numerical model of a sudden stratospheric warming are investigated by tracing a large number of marked particles. The model is adapted from that described by Holton (1976). A sudden stratospheric warming is simulated by allowing a large amplitude, single harmonic wave forced at the lower boundary of the model to interact with the zonal mean flow. The results of a model simulation involving zonal wavenumber 2 are reported. Rings of marked particles are placed along latitude circles at the time when the forcing is turned on at the lower boundary and their motions are traced for a period of 30 days. The particle displacements near the level of maximum warming are described in detail, the trajectories of particles exhibit two different types of characteristics depending upon whether the particles originate from high or low latitudes. The particle motions are therefore described in terms of two regimes, the polar and the tropical regimes. The polar r...