(Haynes, Manney, Pan)

1. UTLS Workshop Session 1, Monday AM:UTLS Dynamical Structure, Tropopause (Haynes, Manney, Pan) Theme: Tropopause Structure, Focus on Tropopause Inversion layer (TIL) and Double Tropopauses (DTs)

2. TIL and DT: (1) Observational Characterization • Randel TIL “Happens everywhere, all the time”…. Well, not quite. • Hegglin&Gettelman: Overall seasonal evolution of TIL captured in CCMVal climate models • Schmidt et al: GPS climatology of DT, N2, tropopause sharpness; compared with MOZAIC • Grise et al: N2 climatology from GPS data; relation to stratospheric processes; possible secondary TIL • Randel et al (poster): TIL structure from GPS • Phillips (poster): Observed structure/evolution of DTs in HIRDLS data • Homeyer (poster): Sonde data; resolution effects in characterization of tropopause; characteristics of sharp/broad tropopause regions • Tandon: (poster) Spatial structure and variability of TIL from GPS, analyses • Themes/Questions: • GPS data rock! Broaden usage of them further? Use with more diverse • trace gas datasets? • Exact definitions of TIL? Resolution issues?

3. TIL and DT: Observational Characterization Homeyer et al, sharp and broad tropopause profiles

4. TIL and DT: (2) Mechanisms/Processes • Wang et al: DT in BC lifecycle experiments; flows with jets consistent with strong TIL result in more DTs • Kunz et al: Modeled H2O profiles consistent with mixing lead to enhanced TIL via radiative effects • Birner et al: “Stratospheric radiative equilibrium” solutions give lower/higher tropical/ET tropopause, little winter TIL, strong summer TIL; adding back dynamics restores winter TIL • Randel et al (poster): Radiative effects of H2O result in strong summer TIL in polar regions • Tandon et al (poster): Radiative calculations suggest H2O can be strongly coupled to TIL strength • Comments/Issues: • Can get TIL-like structure via purely dynamical mechanisms • O3 radiative effects also contribute • What is interplay of mechanisms as a function of season, latitude?

5. TIL and DT: (3) Connections/Relevance • Relation to chemical structure/evolution: • Hegglin&Gettelman: Several CCMVal diagnostics relate CO, O3 structure to tropopause, eg, CO gradients with re tropopause, CO & O3 profiles relative to tropopause • Schmidt et al: MOZAIC CO & O3 vs N2; tracer gradient correlations • Kunz et al: TIL & TFM (“fresh tropospheric air”) mixing branches • Wang et al: Mixing in DT region in BC lifecycle experiments (doesn’t agree well with obs??) • Tandon et al (poster): O3 in strong vs weak TIL cases • Relationships of TIL/DT, overall dynamical structure: • Wang et al: TIL as characteristic of flow related to generation of DT? • Homeyer et al (poster): Relation of sharp (strong TIL) and broad (weak or no TIL) cases to vorticity, latitude, etc • Tandon et al (poster): TIL on cyclonic/anti-cyclonic side of jet

6. TIL and DT: (3) Connections/Relevance • Questions: • How important is TIL to overall dynamical and chemical structure of UTLS? • How important are DTs to overall dynamical and chemical structure of UTLS? • That is, why do we care about details of TIL, DT structures? Tandon et al: sharper tropopause O3 gradients in strong TIL cases