Singular vectors and their nonlinear evolution during the January 2009 stratospheric sudden warming

Abstract

AbstractThe evolution and structure of stratospheric singular vectors (SVs) during the major stratospheric sudden warming (SSW) of January 2009 are investigated. SV analyses, optimized for growth at stratospheric levels over 72 h, were examined for selected dates before and during the SSW. It was found that the initial and final SV fields have larger horizontal structures during the SSW event than before the SSW event. A high‐altitude forecast model was initialized with perturbations taken from the initial time SV structures and integrated for 144 h to study growth and nonlinear changes in a highly disturbed polar vortex. When large‐amplitude initial SV perturbations were forecast during the SSW, large changes occurred in the descent of the SSW event and poleward focusing of the Eliassen–Palm fluxes. Examination of the development of SV analysis suggests that stratospheric SV growth occurs through wave‐action conservation as initial SV perturbations propagate into the polar vortex jet.