| Summary: | Observations from the Microwave Limb Sounder (MLS) on NASA's new Aura satellite give an unprecedentedly detailed picture of the spring Antarctic polar vortex breakup throughout the stratosphere. HCl is a particularly valuable tracer in the lower stratosphere after chlorine deactivation. MLS HCl, N2O, H2O broke up in the upper stratosphere by early October, in the midstratosphere by early November, and in the lower stratosphere by late December. The subvortex broke up just a few days later than the lower stratospheric vortex. Vortex remnants persisted in the midstratosphere through December, but only through early January 2005 in the lower stratosphere. MLS N2O observations show diabatic descent continuing throughout November, with evidence of weak ascent after late October in the lower stratospheric vortex core.
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