|Goodman, J. C. and A. Czaja,, Why the West Wind Wobbles: Viewing Annular
Modes as Stochastically-Excited Potential Vorticity Reservoirs, submitted to Quarterly Journal of the Royal Meteorological Society, 2006|
The Northern and Southern Annular Modes can be thought of as modulating the polar pools of high potential vorticity (PV). Meridional PV fluxes caused by synoptic weather stochastically add or remove PV from this reservoir, gradually increasing or decreasing the strength of the annular mode. We demonstrate that much of the variability of the annular modes in both a 3-layer quasigeostrophic model and in NCEP-NCAR reanalyses can be explained by this simple stochastic process.
FILE » Annular Modes 2006