Structure and Chemical Composition of the Extratropical UTLS Issues, Progresses, and Challenges (with a focus on airborne research) Peter Hoor and Laura Pan UTLS workshop, October 2009

UTLS workshop, Boulder, Oct Introduction 2. Milestones of airborne research 3. Progresses and arising questions trace gas distribution, coordinate systems and definition of atmopheric regimes dynamical structure, tropopause and interaction with tracers 4. Challenges (by Laura) Outline

UTLS workshop, Boulder, Oct.2009 A Conceptional View: Processes

Introduction concept of the 'lowermost stratosphere' integration of theoretical concepts with observations

UTLS workshop, Boulder, Oct.2009 The early days of airborne research...

UTLS workshop, Boulder, Oct : Exchange in the vicinity of a TP-fold - bidirectional - relation of potential vorticity and thermal tropopause Postulation of mixing and exchange layer Milestones Edwin Danielsen: Postulation of a mixing and exchange layer (1968!!!)

UTLS workshop, Boulder, Oct : Processes (clear air turbulence and tracer flux) Postulation of mixing and exchange layer Shapiro: Clear air turbulence and turbulent tracer flux Milestones

UTLS workshop, Boulder, Oct.2009 Milestones Dessler: The GLOBAL lowermost stratosphere is affected on the large scale by air of non-tropical origin

O3 -CONOy/O3 -N2O Fischer: Tracer interrelationships indicate an intermediate between 'tropospheric' and 'stratospheric' composition (STREAM 1997) Milestones

UTLS workshop, Boulder, Oct.2009 Ray et al., 1999 Milestones Quantification of downward transport across 380K on the basis of in-situ measurements

UTLS workshop, Boulder, Oct.2009 A community was born...

UTLS workshop, Boulder, Oct.2009 Tropopause workshops: Bad Tölz (SPARC 2000) Mainz (SPARC / IGAC 2005) stimulated a lot of activities and measurements and contributed to our current understanding many perspectives and different views on that region Boulder 2009: Reconcilation and future direction?! A community was born...

UTLS workshop, Boulder, Oct.2009 Conclusions/outlook: Mainz 2005 It is clear that consistent use of welldefined terminology (c.f. STE=STT+TST) is imperative, so that disparate studies can be integrated for a larger-scale picture. In this regard there is especially a need to better understand the newly identified ExTL. Given the complex thermodynamic and chemical state in this region, what metrics should be used to define the ExTL? What is its special role in the chemical, physical and dynamical state of the extratropical UTLS?

UTLS workshop, Boulder, Oct.2009 Progresses since... trace gas distribution, coordinate systems and definition of atmopheric regimes

 [K] equivalent latitude CO [ppbv]  [K] latitude CO [ppbv] SPURT: First consistent UTLS data set with given horizontal, vertical and temporal coverage Progress  [K] CO Tropopause (2PVU) Tropopause-following mixing layer (2 PVU) and weak seasonality in Delta Theta Hoor et al., 2004, Engel et al.,2006

Pan et al., 2004 Quantification of layer properties 'ExTL' (WMO, 2003) Chemical transition layer above an below the termal tropopause Progresses

UTLS workshop, Boulder, Oct.2009 Boundaries of the 'ExTL' from ACE observations Hegglin et al., 2009 H2O-based CO-based ExTL-top: different latitudinal dependencies depending on tracer Progresses

UTLS workshop, Boulder, Oct.2009 thermal TP TIL tropopause inversionlayer (TIL) and tracer Birner, 2002 Hegglin, 2009 Progress

UTLS workshop, Boulder, Oct.2009 Berthet et al., 2006 Progresses: TST Berthet et al: Time scales and seasonality of coupling tropopause definition Probability of a trajectory of having resided in the boundary layer within the last 30 days

Hoor et al., 2005 extratropical tropical stratospheric winter spring autumn summer relative fraction Progresses: Quantification of different sources seasonality of fractional contribution from different regions to the compoition of the LMS

UTLS workshop, Boulder, Oct.2009 Boenisch et al, 2009 Mean transit time distribution for air masses transported into the lowermost stratosphere May August Progress Mean age and mass fraction of 'fresh' tropospheric air entering the LMS (on the base of measurements and bimodal age spectra)

UTLS workshop, Boulder, Oct.2009 Seasonality of a ”chemically defined” LMS from ACE observations Hegglin et al., 2007 N2O-O3-correlations Progresses Sep Mar

UTLS workshop, Boulder, Oct.2009 altitude [km] equator pole polarjet stratosphere troposphere 380 K 360 K 340 K 320 K winter subtropical jet An integral view?

UTLS workshop, Boulder, Oct.2009 altitude [km] equator pole polarjet stratosphere troposphere 380 K 360 K 340 K 320 K winter subtropical jet An integral view?

UTLS workshop, Boulder, Oct.2009 Integral view ? Chemical structure of the lowermost stratosphere: - transition layer which extending around the tropopause - the vertical depth: 2-4 km relative to the tropopause K above 2 PVU tracer dependency, tropopause - chemical transition layer marks a change in transport time from the lower troposphere to the LMS - strong seasonality above the transition layer: - 'young' air in summer and autumn - rapid 'flushing' from late spring to summer - strong coupling to the TTL and tropical lower stratosphere

UTLS workshop, Boulder, Oct.2009 Birner, 2006Randel, 2007 Challenges Which dynamical processes are most important for the observed chemical structure, particularly the strong coupling to the tropics? What is the role of transport and mixing in maintaining the dynamical structure of UTLS? Are there feedbacks between dynamical structure and composition ? How robust are the estimated budgets?

UTLS workshop, Boulder, Oct.2009 Even more challenges...

Hoor et al., 2004 CO in different tropopause based coordinate systems Coordinates CO relative to the thermal and to the dynamical (2 PVU) tropopause  [K] CO Tropopause (2PVU) Pan et al., 2004 thermal tropopause

UTLS workshop, Boulder, Oct.2009 Relation of various tropopause definitions to chemical structure Hoor and Hegglin, in prep. Progresses themal tropopause ozone gradient derived tropopause 2 PVU

Progress Stratospheric downward flux across the tropopause and ozone at the 'chemical tropopause Zahn et al.,,2004.

Coordinates jet based coordinates

Ozone (15-45 hPa above 2 PVU) from MOZAIC, Thouret et al., 2006 Coordinates

Published by AAAS T. P. Marcy et al., Science 304, (2004) measurements: - Hcl – O3 -correlation Identification/quantification of downward transport of ozone Progress

Quantify downward flux across the tropopause and help to constrain models? Hsu and Prather, 2008

Challenges How do we reconcile the extratropical tropopause definitions? How do we best link the tropopause definitions to the trace gas observations? How do we link both to the underlying dynamics? How quantitative can we get with budgets and 'empirical' global fluxes? Can we derive long-term changes? How do we have to design future measurements / instruments / campaigns ?

UTLS workshop, Boulder, Oct.2009

Open questions I What do we mean with: - ExTL (from CO, H2O, time?), mixing layer, ExUTLS, chem. LMS Remember: “It is clear that consistent use of welldefined terminology is imperative, so that disparate studies can be integrated for a larger-scale picture.“

UTLS workshop, Boulder, Oct.2009 Open questions I What do we mean with: - ExTL (from CO, H2O, time?), mixing layer, ExUTLS, chem. LMS Remember: “It is clear that consistent use of welldefined terminology is imperative, so that disparate studies can be integrated for a larger-scale picture.“ How to integrate observations to an integral picture? - which aspect should be emphasized? Time? region? Dynamical or geometrical aspects?

UTLS workshop, Boulder, Oct.2009 altitude [km] equator pole polarjet stratosphere troposphere 380 K 360 K 350 K 335 K summer A Conceptional View: Composition subtropical jet

UTLS workshop, Boulder, Oct.2009 Birner, 2006Randel, 2007 Open questions I -feedback between structure and composition -wave propagation and temperature changes due to altered chemical composition What is the role of transport and mixing in maintaining the dynamical structure of UTLS? e.g. H 2 O and N 2

 [K] equivalent latitude CO [ppbv] eqivalent latitude Hoor et al., 2004, Engel et al.,2006  [K] latitude CO [ppbv] SPURT: First consistent UTLS data set with given horizontal, vertical and temporal coverage Progress Tropopause-following mixing layer (2 PVU) and weak seasonality in Delta Theta

'process related' - coordinates, Brioude et al., 2007 Coordinates

UTLS workshop, Boulder, Oct.2009 Boundaries of atmospheric regions from ACE observations Hegglin et al., 2007, 2009 ExTL-boundaries 'chemically-defined' LMS Progresses Sep Mar

UTLS workshop, Boulder, Oct.2009 Troposphere Stratosphere Transport Stratosphere Troposphere Transport Stratosphere Troposphere Exchange Progresses: Transport across the tropopause Sprenger + Wernli 2003: Location and seasonality of cross tropopause transport

UTLS workshop, Boulder, Oct.2009 Hoor et al., 2002 Mixing lines and LMS-layer structure ('mixing layer'), seasonal behaviour Progresses Delta Theta coordinates, dyn. TP

Introduction Kind of 'starting point': Summarizes the state of the art dynamical concepts and understanding of atmospheric dynamics (e.g. Hoskins, McIntyre, Haynes, Appenzeller....) -the role of the extratropical tropopause - physical (transport related) difference between 'overworld' and middleworld (timescales and role of isentropes CONCEPT of LOWERMOST STRATOSPHERE MERGING of theretical concepts with existing observations...which where