UTLS Transport & STE Summary “Finding Nemo” Gettelman, Neu, Mullendore

Summary of Presentations (1) Haynes: Dynamical theories for extratropical tropopause height No single definition is perfect. Trends matter! Tropopause & climate Pan: START 08: mixing in disturbed cases. Mixing happens not in the jet core but above and below jet. Tilmes: Difference in mixing (Relative Altitude) between Sub-Tropics and Polar from in-situ data. Trace- tracer correlations. "regional differences more pronounced than seasonal differences” Ray: START08 Transport: "Low Road" v. "High Road”. Different time scales. Short transit times above tropopause up to Jet Top (intrusions) Vogel: CLaMS Lagrangian model shows air mass origins for START08 RF1 (intrusion) RF4 (fold). Coherent air mass origins! TTL air in LMS high lat Stone: START08 WACCM nudged simulations of an intrusion Method for mapping intrusions in a global model

Summary of Presentations (2) Zhang: GW during START08: Topographic waves dominate over Rockies Tarasick: "Radar Tropopause" can pick out humidity gradients. Stratospheric intrusions common with rapid changes in trop height. Gille: HIRDLS O3: Less mixing in winter, more in spring. PV & O3 correlated. Above 350K: Not much mixing or affect on O3. Santee: MLS: Vortex & chemical processing of LMS air. Interannual variability large. O3 export to mid-lats (especially SH) Massie: Smoke in Lower stratosphere (at tropopause). CALIPSO, MLS CO Rise does not appear due to convection. Are analyses good enough? May be due to absorptive heating of smoke. Konopka: PDFs of O3/CO are good for comparison of Data and Models. Single mixing parameter (Kunz 2009). CLaMS agrees with START08

Summary of Presentations (3) Hoor: CO & H2O definitions of ExTL are Different: different sources/sinks CO =PV following. H2O preserves last saturation. James: PreAVE and CR-AVE aircraft in Tropical & Subtropical UTLS Air parcel origins. Tropical origin and synoptic perturbations mix. Miyazaki: High vertical resolution GCM model results. TIL stronger at high resolution. TIL maintained by radiation and heat budget. 'Small scale' waves contribute to mixing Mizuta: STE in a high horizontal resolution model. Gross STE smaller at high resolution. Net STE does not depend on resolution. Moustaoui: TREX & modeling studies of mountain waves. modulation of O3 & CO depends on background tracer gradients Barth: 4km Simulation of O3 over US. O3 due to Lightning NOx, convective precursor transport and STE (preliminary)

Discussion Points (1) Structure of Extratropical Tropopause: Baroclinic eddies (Haynes) – Modified by moist processes – consistent theories, not fully unified – Tropopause is a fingerprint of climate change (see later today) START08: Tracer-Correlations – Mixing regions: can see origin of mixing lines. – source of air, transport pathways (CLaMS, Ray, James) – Typical or not? (Gille: O3 follows PV) TIL Structure & Chemical aspects to it (Hoor) – TIL maintenance: Radiation & Vertical Velocity (Miyazaki) – Dynamical structure corresponds to tracer structure – Profiler responds to H2O gradients (Tarasick: intrusions, TIL)

Discussion Points (2) Tropopause folds and jet structures: – High Resolution Model, START08, WRF in N. American Monsoon – Trop folds associate w. storm tracks (STE v. convection hard). Gravity Waves: Perturb tracer fields, role in mixing. – Importance of mid scales in high resolution models.

Discussion: ‘Integral’ View (Nemo!) PV and Static stability related – So TIL is a mixing barrier – ExTL is a result of this mixing barrier: different depth for tracers with different sources Maintenance: TIL & PV Tropopause related – TIL: result of O3 and w-convergence – Tropopause: TIL + Baroclinic eddies + BD Circ ExTL/TIL breaks down where mixing occurs – Folds, Intrusions, Fronts – Small scale (GW, ‘mixing’) where events occur – Important for STE