Planetary wave energetics and polar vortex variability

What is it about?

We look at the problem of the variability of the stratospheric polar vortex from the point of view of planetary wave energetics. We find that positive (negative) anomalies of the energy associated with the first two baroclinic Rossby modes m=1 and m=2 of planetary wave s=1 are followed by the downward progression of negative (positive) anomalies of the vortex strength. Composite analysis of displacement- and split-type stratospheric sudden warming (SSW) events reveal different dynamics. Displacement-type SSWs are forced by positive anomalies of the energy associated with the first two baroclinic modes of planetary Rossby waves with zonal wavenumber 1. Split-type SSWs are in turn forced by positive anomalies of the energy associated with the planetary Rossby wave with zonal wavenumber 2, and the barotropic mode appears as the most important component. In respect to stratospheric final warming (SFW) events, obtained results suggest that the wave dynamics is similar to the one in displacement-type SSW events.

Featured Image

Why is it important?

This analysis differs from traditional methods in that we have concentrated on a diagnosis of the energy associated with the forcing waves instead of analyzing Eliassen–Palm fluxes. Another difference from previous studies relates to the fact that instead of being restricted to the extratropical subdomain, our analysis is applied to the whole atmosphere, and the relevant circulation components are selected by means of projections onto 3D global functions that allow partitioning the atmospheric global circulation into planetary Rossby waves and inertio–gravity waves with barotropic and baroclinic vertical structures.