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 & climatePan: 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 intrusionMethod for mapping intrusions in a global model

Summary of Presentations (2)Zhang: GW during START08: Topographic waves dominate over RockiesTarasick: "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 UTLSAir 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 athigh 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