1 Ozone „Recovery“ in a Changing Climate M. Weber Universität Bremen FB1, Institut für Umweltphysik (iup) GSPARC Meeting, Berlin, 4-5 December 2006

2 Processes attributed to ozone variability processes intereract with each other  radiation – chemistry - dynamics coupling  high ozone variability (particularly in NH) 3/1997 3/1999 GOME

3 Coupling between chemistry and transport Update Weber et al low planetary wave driving weak Brewer-Dobson circulation high planetary wave driving strong Brewer-Dobson circulation

4 Chemical-dynamical coupling Update Weber et al GOME October March

5 Dynamical control of ozone chemistry: chlorine activation Update Weber et al GOME Sept 1-15 March 1-15 high PSC volume Low T low PSC volume High T

6 recent trends solar wave driving aerosol EESC TO3 trends up to 2003 Dhomse et al. (2006)

7 recent trends solar wave driving aerosol EESC Two more years of data (up to 2005) Update Dhomse et al. (2006)

8 What about SH mid- to high latitudes?  Eddy heat flux calculation less reliable in SH/ better use Vpsc as a proxy for temperature and dynamical variability  Differences to NH:  larger QBO contribution in spring  Little influence from major volcanic eruptions (why?)  EESC turnaround modest (like in NH), linear trend will fit as well, little seasonal variation in trends

9 Solar response in total ozone  Higher response at high latitudes indicates coupling of solar radiation and atmospheric dynamics (via temperature) SBUV/TOMS merged data sets Change from solar min to solar max (regression model )

10 Available (new) satellite data towards WMO 2010  SBUV2 (NOAA 18?)  SCIAMACHY/ENVISAT (2002-)  OMI/AURA(2004-)  GOME2/METOP-1 (2006-)  Potential GSPARC activities:  WFDOAS TO3 (Coldewey- Egbers et al., Weber et al., 2005) from SCIAMACHY, OMI, and GOME2  Nadir O3 profiles (Hoogen et al., 1998, Tellmann et al., 2004) from SCIAMACHY, OMI, and GOME2

11 GOME/SCIAMACHY- Brewer TO3 intercomparison  No seasonal variation in differences to Brewers, but a constant offset from GOME to SCIAMACHY  TOMS, OMITOMS have a seasonal variation of ±1% wrt Brewers NH midlatitude region (18 Brewer stations) GOME SCIAMACHY 2003  GSPARC activities:  Homogenisation of ozone data from multiple satellites  Ozone trend analysis (columns and profiles) beyond solar minimum in 2007

12 Stratospheric water vapor and circulation changes  Water vapor anomaly above tropical tropopause (see also Randel et al., 2006)  BD circulation strength increase in both hemispheres  Persistent low H2O since 2001 to the present  BD circulation changes since 2001 contributed to a ~0.5 K cooling near tropical tropopause  POAM, SAGE, and HALOE ceased operating! Dhomse et al., ACPD

13 SCIAMACHY H2O vapor limb retrieval  Global H2O and HDO(?) data from 2002 to present  Profiles can be retrieved up to about 20 km  Need for tropospheric correction from nadir measurements (tropospheric H2O, cloud parameters, and albedo)  GSPARC activities:  Global H2O limb profile data from SCIAMACHY for trend assessment 910 – 960 nm 3 H2O polyad

14 SUMMARY  Homogenisation of total (and profile) ozone data from GOME, SCIAMACHY, and GOME2 and trend analysis for the next ozone assessment (WMO 2010)  Ozone trend assessment (ozone recovery)  Quantification/refinement of the relative contribution of dynamical and chemical factors to ozone variability  Ozone-climate interaction  Water vapor profiles from SCIAMACHY (2002-)  Are there persistent circulation changes as suggested by the water vapor observations? Are they signs of a changing climate? Contributions to following SPARC themes: -Climate-Chemistry Interactions -Detection, Attribution, and Prediction of Stratospheric Change

15 ozone and solar cycle variability Hood et al., 2006  Models do not show the double peak (25 and 50 km altitude) in sol  Possible reasons  Data record too short (~2.5 solar cycles)  NOx from particle (electron precipitation) leads to ozone destruction during solar minimum in middle stratosphere -> BUT: requires „huge“ amounts of Nox  Reduced ozone production (less sunlight) in middle stratosphere from enhanced ozone in the upper stratosphere  Interference from QBO (not well represented in models) and associated dynamical effects  Lower stratospheric solar signature are probably from dynamical response to solar variability that are insufficiently reproduced in models models observations

16 NH u and T response to solar cycle  Change in zonal mean wind (u) in m/s and zonal mean temperature (T) in K for a change of 113 solar flux units (F10.8 units ) from a multi-variate regression of ERA40/ECMWF ( ) TT uu temperature response in tropics More westerly SJ  Solar max: major warmings in late winter/weak polar vortex in late winter  Solar min: major warmings in early winter/strong polar vortex in late winter higher Arctic T and weakening of westerlies in mid- to late winter Downward propagation of wind anomalies Grey (2003)

17 Open issues from WMO 2006 assessment: Global ozone (Ch. 3)  Vertical structure of the solar cycle response in ozone highly uncertain due to short-record lengths and intercalibration problems of instruments  Cause of stratospheric circulation changes since mid-1990s are unclear (climate change signal?)  Pinatubo aerosol effect in SH are predicted by models, but not evident in observations  Current stratospheric inorganic bromine (Bry) are not consistent with long-lived source gases, models may overestimate mid-latitude column ozone  Interactive models (GCMs) tend to underestimate ozone trends, while non-interactive models (CTMs) generally agree with observations  CTM Models (2D and 3D) generally perform better in the NH than in the SH when compared to observations

18 Open issues from WMO 2006 assessment: Polar Ozone (Ch. 4)  Although the forcing of polar temperatures and vortex strength from planetary and gravity waves are well established, the causes of forcing variability (on dcadal scale) are still unknown  Cold Arctic winters have gotten colder over four decades, the temperature change exceeds that expected from changes in greenhouse gases, the reason for this is still unknown  The triggers of the unusual planetary waves related to the first major stratospheric warming over the Antarctic 2002 are unknown, was this a random event due to internal atmospheric (natural) variability or may it be related to climate change  BrO may play a larger role in polar ozone loss (up to 50%), but there is still large uncertainty in the polar bromine budget.  The exact NAT nucleation mechanism is till not completetly understood, although progress has been made in parameterising denitrification in models.

19 SPARC initiatives and themes 1 - Climate-Chemistry Interactions Theme leaders: Granier (France), Peter (Switzerland), Ravishankara (USA)  What are the past changes and variations in the stratosphere?  How well can we explain past changes in terms of natural and anthropogenic effects?  How do we expect the stratosphere to evolve in the future, and what confidence do we have in those predictions? 2 - Detection, Attribution, and Prediction of Stratospheric Change Theme leaders: Randel (USA), Shepherd (Canada)  How will stratospheric ozone and other constituents evolve?  How will changes in stratospheric composition affect climate?  What are the links between changes in stratospheric ozone, UV radiation and tropospheric chemistry?

20 SPARC initiatives and themes (2) 3 - Stratosphere-Troposphere Dynamical Coupling Theme leaders: Baldwin (USA), Yoden (Japan)  What is the role of dynamical and radiative coupling with the stratosphere in extended-range tropospheric weather forecasting and determining long- term trends in tropospheric climate?  By what mechanisms do the stratosphere and troposphere act as a coupled system?