On the Meridional Structure of Annular Modes

Using a simple stochastic model, the authors illustrate that the occurrence of a meridional dipole in the first empirical orthogonal function (EOF) of a time-dependent zonal jet is a simple consequence of the north–south excursion of the jet center, and this geometrical fact can be understood withou...

Full description

Bibliographic Details
Published in:Journal of Climate
Main Authors: Wittman, Matthew A. H., Charlton, Andrew James, Polvani, Lorenzo M.
Format: Article in Journal/Newspaper
Language:unknown
Published: American Meteorological Society 2005
Subjects:
Online Access:https://centaur.reading.ac.uk/1572/
https://doi.org/10.1175/JCLI3394.1
Description
Summary:Using a simple stochastic model, the authors illustrate that the occurrence of a meridional dipole in the first empirical orthogonal function (EOF) of a time-dependent zonal jet is a simple consequence of the north–south excursion of the jet center, and this geometrical fact can be understood without appealing to fluid dynamical principles. From this it follows that one ought not, perhaps, be surprised at the fact that such dipoles, commonly referred to as the Arctic Oscillation (AO) or the Northern Annular Mode (NAM), have robustly been identified in many observational studies and appear to be ubiquitous in atmospheric models across a wide range of complexity.