1. Satellite Observations and Simulations of Subvortex Processing and Related Upper Troposphere / Lower Stratosphere Transport M.L. Santee, G.L. Manney, W.G. Read, N.J. Livesey, L. Froidevaux Jet Propulsion Laboratory, California Institute of Technology R.S. Harwood Edinburgh University The Extra-Tropical UTLS: Observations, Concepts and Future Directions Community Workshop at NCAR October 19-22, 2009 National Aeronautics and Space Administration

2. 22 Overview of Subvortex / Extratropical UTLS Study  Export of chemically-processed, ozone-depleted air from the polar vortex in late winter / spring can significantly affect trace gas distributions throughout the extratropics  Chemically-perturbed air is largely confined within the vortex until it breaks down, but the degree of containment varies with altitude  Subvortex: Region below strong confinement of the vortex proper  Low temperatures and polar processes also occur in the subvortex, but it experiences more vigorous exchange with lower latitudes  Vortex / subvortex transition varies throughout the season from ~350 to 380 K in the Antarctic and from ~400 to 450 K in the Arctic  We use Aura MLS & ACE-FTS measurements of HNO 3, H 2 O, O 3, HCl, and ClO to investigate seasonal, interannual, and interhemispheric variations in chemical processing in the lowermost stratosphere  Observed trace gas variations are compared with the evolution of transport barriers from GMAO GEOS-5 meteorological analyses  MLS data are also compared with SLIMCAT 3D CTM simulations

3. 33 Seasonal “Snapshots” of the Antarctic Vortex & Subvortex – I  Mid-August: HNO 3 and H 2 O depleted down to bottom of vortex; O 3 still high throughout vortex / subvortex  Mid-September: HNO 3 slightly recovered; H 2 O more depleted; polar O 3 loss substantial  Mid-October: HNO 3 & H 2 O significantly recovered; O 3 severely depleted throughout vortex & subvortex  2006 record O 3 hole: partly due to large losses in the subvortex White contours: Tropopause (1.5, 4.5 PVU) Black contours: Vortex edge, Subtropical jet HNO 3 H2OH2OO3O3

4. 44 Chlorine Activation in the Antarctic Lowermost Vortex & Subvortex  In 2006, CALIPSO observed PSCs at 10–15 km from late June to mid-September [Pitts et al., 2007]  MLS & ACE data show that in mid- September HCl and ClONO 2 are depleted and ClO is enhanced  Thus substantial chlorine activation is widespread inside the Antarctic lowermost polar vortex / subvortex MLS HClMLS ClO ACE-FTS ClONO 2 10-day averages

5. 55 Seasonal “Snapshots” of the Antarctic Vortex & Subvortex – II  Mid-November: Low HNO 3 & H 2 O imply denitrification & dehydration; O 3 recovery significant  Mid-December: Vortex starting to erode; homogenization of trace gas contours suggests exchange of polar & midlatitude air  Mid-January: Major transport barrier is now subtropical jet / tropopause; signature of dehydration brought down by descent HNO 3 H2OH2OO3O3

6. 66 Seasonal “Snapshots” of the Arctic Vortex & Subvortex  2004 / 2005: Very cold in lower stratosphere  Mid-January: HNO 3 substantially depleted, but no significant dehydration  Mid-February: HNO 3 depletion still evident  Mid-March: Substantial O 3 loss, mostly above ~12km; the minimum in polar lowermost stratospheric H 2 O is not from dehydration aloft (as in Antarctic) but from influx of drier tropical air HNO 3 H2OH2OO3O3

7. 77 Evolution of Transport Barriers and MLS Trace Gases

8. 88 Evolution of Trace Gases from MLS and SLIMCAT

9. 99 Comparison of Aura MLS and ACE-FTS Measurements Aura MLS ACE-FTS  Aura MLS and ACE- FTS data generally show very consistent features

10. 10 Summary & Conclusions  More than 5 years of Aura MLS v2.2 measurements were analyzed along with GEOS-5 meteorological data to investigate interhemispheric and interannual variations in chemical processing and transport barriers in the lowermost stratosphere  Polar processing ― denitrification, dehydration, chlorine activation, and ozone loss ― occurs throughout the lowermost polar vortex and down into the subvortex  The breakdown of the vortex at the end of winter allows mixing between polar-processed and lower-latitude air  At this time a transition takes place from the vortex to the subtropical jet / tropopause being the major transport barrier  Trace gas variations in the UTLS observed by Aura MLS are consistent with:  the evolution of transport barriers (from meteorological analyses)  Variations simulated by the SLIMCAT 3D CTM  Variations observed by ACE-FTS