Dynamical Control on Decadal Ozone Change S. Dhomse 1, M. Weber 1, I. Wohltmann 2, M. Rex 2, V. Eyring 3, M. Dameris 3, and J.P. Burrows 1 (1)Institute of Environmental Physics, University Bremen, Bremen (2)Alfred-Wegner Institute for Polar and Marine Research, Potsdam (3)Institute of Atmospheric Physics, DLR Oberpfaffenhofen

Overview Data sources: TOZ :- GOME V3, TOMS V7, TOMS-SBUV merged dataset Met Analyses:- ERA40, UKMO, NCEP GCC:- ECHAM/DLR E39/C Topics:  Planetary wave driving and ozone (introduction)  Heat flux and spring/fall ozone ratio – Interhemispheric linkage  ERA40 – Problems in SH(!) and NH(?)  Multivariate regression analysis (preliminary results)  Summary and Conclusion

Annual cycle in total ozone

Interannual variability Winter/spring ozone Photochem. summer decay

Annual cycle of GOME total ozone in NH and SH NH SH  Winter gain through transport in ozone outweighs chemical ozone loss in NH  In SH, chemical ozone loss is larger than winter transport, except 2002.

 Heat flux starts increasing in fall  NH heat flux is generally higher than in SH Annual cycle of heat flux in NH and SH 3 day mean time series

Tropospheric forcing and spring/fall ozone ratio  GOME ozone ratio  50°-90°  Sep over Mar (SH) Mar over Sep (NH)  Winter heat flux  43°-70°  100 mbar  Sep-Mar (Mar-Sep) integrated and averaged SH anomaly 2002 Cold Arctic winter/spring seasons Update from Weber et al For SH :-

Update from weber et al Tropospheric forcing and chlorine activation  OClO  BrO+ClO –> OClO + O  Measured in twilight inside the polar vortex  Maximum vertical column at 90° solar zenith angle integrated over the winter  Below 92°SZA OClO is a measure of chlorine activation UKMO High chlorine activation persisted during SH anomaly 2002

Correlation coefficients for selected latitude bands Jan/Aug Feb/Aug Mar/Aug Apr/Aug May/Aug Jan/Sep Feb/Sep Mar/Sep Apr/Sep Oct/Sep Jan/Oct Feb/Oct Mar/Oct Apr/Oct May/Oct Sig. Level > 99% Sig. Level < 95% Sig. Level > 95% Nearly identical results using TOMS,TOMS/SBUV merged dataset

Ozone winter gain and summer transition  ERA40 vs UKMO  Interannual variability of winter heat flux correlates well with winter ozone gain  Winter heat flux higher in ERA40 (too much transport)  E39/C vs GOME  lower interannual variability in winter (NH)  weaker wave driving in SH (cold bias?)  Photochemical decay about 3m (>50°N) and 2.5 m (>62°N)  Good agreement between GOME and E39/C

ERA40 in Early 80s vs. late 90s  Correlation with ERA40 in early 80s and SH very poor  What is changing ? Dynamics or chemistry? ERA40

1957 / 09 – 1957 / / 12 – 1972 / / 05 – 1972 / / 01 – 1974 / / 05 – 1974 / / 07 – 1985 / / 04 – 1986 / / 04 – 1988 / / 11 – 1988 / / 01 – 1994 / / 01 – 1995 / / 05 – 2002 / 08 ERA40 in various streams

Long term trend Difference March-September 50°N-90°N  Linear regression terms: const, linear, aerosol & heat flux

Long term trend Difference March-September 50°N-90°N  Linear regression terms: const, linear, aerosol & heat flux  Linear: r=0.88, EESC: r=0.89, no linear term: r=0.83  “Linear“ term not statistically significant (3  ): instrumental drift/bias /met analysis quality 80s vs 90s

Summary & Conclusion  Compact relationship between winter ozone gain and seasonal heat flux for both hemispheres (late nineties/early 2000)  Winter chlorine activation shows good correlation with wave driving  Summer ozone levels are tied to wave activity of the previous winter (see also Fioletov and Shepard 2003)  Met. Analyses  good measure of interannual variability  differences in strength of high latitude ozone transport varies (ERA40 higher than NCEP/UKMO)  Correlations between wave driving & ozone particularly well in 90s  ERA40 seems inconsistant in SH in presatellite era  E39/C (and possibly other CCMs)  less interannual variability in winter  No summer minimum in SH

 Multivariate regression of spring-fall difference at high latitudes  Linear term is not significent  Largest contribution from aerosol and heat flux Summary & Conclusion

Candidoz: 3 rd Year WP 3: Residual circulation and Tropospheric Coupling:  Systematic investigation of interhemispheric linkage (latitude bands and diffrent periods)  Cumulative effect over winter is not necessarily linear  Multivariate regression using different latitude bands with CANDIDOZ proxies  Use of GOME neural net O3 profile data ( )  TEM transport diagnostics (in collabaoration with AWI)  EP flux correlation with the zonal mean vertical field  EOF analysis of latitude-altitude field

Proxies for statistical trend analysis/O3 changes (1) Longer term variability  Residual circulation  EP flux from preceding winter (most important)  Pol ozone loss  V_psc X EESC (take into account H2O vapour trend, abt. 10%/decade, and bromine, latter is already included)  Dilution proxy (RDF advection of O3 depletion profile, see Knudsen, somewhat dificult to obtain)  Mid-stratosphere homogeneous ozone loss  EESC  Aerosol  Stratospheric extinction (multiplying with EESC)  QBO  2 QBO indices differing by a phase shift of pi/2  Solar cycle  F10.7 cm flux, after 1978 MgII index, sun spot number for older data

Proxies for statistical trend analysis/O3 changes (2) Short term variability (days)  Vertical lifting (TH change)/thickness of O3 layer between TH and photochemical equilibrium (10hPa)  Tropopause pressure (NCEP)/200 hPa Geopotential  Short-term advection (TH change)  Equivalent latitude (bad in summer)/ PV at various altitude (PV trend problem?)

UB Action Item  Inform CANDIDOZ when WFDOAS data are ready  Discuss with Greg Bodeker about using WFDOAS in NIWA dataset  Make MgII index available to Candidoz