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)

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?

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

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?

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

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