The influences of persistent anomalies on Southern Hemisphere storm tracks

Abstract

Empirical orthogonal function (EOF) analysis has been applied to nine years of daily 500-hPa data for the Southern Hemisphere from which synoptic-scale variations had been removed. This resulted in 11 principal modes, accounting for 66% of the variance, which were then regionalized through application of a Varimax rotation. These rotated patterns included a high-latitude mode covering the Antarctic, and eight others defining regional perturbations in the principal storm tracks at high latitudes. Persistent anomalies were defined as spells where the time coefficient of the rotated EOF was greater than 1 standard deviation or less than -1 standard deviation for a period of 10 days or more, and 220 of these spells were obtained for the nine EOFs used in the analysis. -from Authors