Climatology and Variability in Extratropical Multiple Tropopause Regions of Trace Gases from MLS, HIRDLS and ACE-FTS

Climatology and Variability in Extratropical Multiple Tropopause Regions of Trace Gases from MLS, HIRDLS and ACE-FTS

Michael J. Schwartz 1 Gloria L. Manney 2 Michaela I. Hegglin 3 Nathaniel J. Livesey 1 Michelle L. Santee 1

The extra-tropical tropopause region is dynamically complex, frequently including a secondary thermal tropopause that extends from the high-altitude tropical tropopause across the subtropical jet to overlay the primary extratropical tropopause. This tropopause structure is zonally asymmetric and time-varying and, along with the upper tropospheric jets and the stratospheric polar night jet, defines the barriers and pathways that control upper tropospheric/lower stratospheric (UTLS) transport. Double tropopauses can cover large regions, at times extending poleward beyond 60 degrees latitude, and may reach the polar subvortex, particularly during sudden stratospheric warming events. In the upper part of the inter-tropopause layer, above the tropopause inversion layer, parcels often have characteristics suggesting low-latitude and tropospheric origins. The MLS, HIRDLS and ACE-FTS satellite instruments provide a generally consistent picture of both stratospheric tracers (such as O3, HNO3 and HCl) and tropospheric tracers (such as CO, H2O and CH4) within the dynamical context provided by GEOS-5 meteorological fields. Trace gas composites that do not account for tropopause structure (such as zonal or equivalent latitude means) can obscure the roles of transport processes in determining distributions, and so may obscure coupling between UTLS composition and climate. The usefulness of trajectory analyses in providing insight into the origins and destinations of parcels in the inter-tropopause layer will be discussed. 1 Jet Propulsion Laboratory, Cal Tech, Pasadena, CA USA 2 NorthWest Research Associates, Socorro, NM 3 Department of Meteorology, University of Reading, Reading, UK