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2. Tropospheric Circulation Changes in Response to a Stratospheric Zonal Ozone Anomaly - Model Results Dieter H.W. Peters, A. Schneidereit, Ch. Zülicke, I. Kirchner* Leibniz IAP, Kühlungsborn, U Rostock * Institute of Meteorology, FU Berlin SNAP-Reading-25.4.2013 dpe - 1 VARNAER is a DFG funded project in the frame of the PANDOWAE group www.pandowae.de

3. Outline - Motivation => open questions - Methodology =>+ perform two 40-year runs with ECHAM5-MA, forced with AMIP SSTs, from 1960-1999, + further diagnosis of quasi-stationary waves, SSW events, NAM variance, predictability : NAM(p) => AO, poleward RWB events of typ P2 - Model results=> for control run with ZSO3 (O3SYM) for anomaly run with both ZSO3+ASO3* (O3ASYM) - Summary dpe - 2SNAP-Reading-25.4.2013

4. Motivation Open questions: Which surface and tropospheric influences are induced by the zonally asymmetric ozone in the stratosphere? + showing results for a sensitivity study, extension of former similar studies (Kirchner & Peters, 2002; …) How does zonally asymmetric ozone change the dynamical coupling of atmospheric layers? + discussion of mechanism dpe - 3 SNAP-Reading-25.4.2013

5. Sensitivity study with ECHAM5 - Methods I Model configuration: + performed two AGCM - ECHAM5-MA runs (for T42, L39, H top  80km) (Roeckner et al. 2002, Manzini et al. 2006) + runtime interval is 40 years forced with same AMIP SST from 1960 until 1999 but different ozone fields are used: - O3SYM: control run with mean zonally symmetric ozone of the 1990s - O3ASYM: anomaly run with added zonally asymmetric ozone O3* field based on ERA-40 ozone fields of the 1960 – 1999 period including months to months and inter-annual variability Remarks: + implemented O3* field only north of 30° N and between 500 and 1 hPa layer + no trend in zonally symmetric ozone field was considered + due to fixed O3* field any transport of ozone was excluded + aim is to isolate the heating effects of zonally asymmetric ozone dpe - 4 SNAP-Reading-25.4.2013

6. Structure evolution of decadal zonally asymmetric O3* Mean O3* at 20 hPa dpe - 5 + wave-1 structure in zonally asymmetric ozone + increase and decadal variability in ozone amplitude SNAP-Reading-25.4.2013 1990s 1960s ERA-40 Winter (DJF)

7. Quasi-stationary wave change for January – Result I SNAP-Reading-25.4.2013 + westward shift of the vortex by about 60 degree + significant (95 %) in the middle and lower stratosphere for O3* anomaly run in January Difference O3ASYM – O3SYM dpe - 6

8. Sensitivity study with ECHAM5 – SSW – Result II + number of major SSW events without final dpe - 7 + significant increase of major SSW events in 1980/90s for O3ASYM run SNAP-Reading-25.4.2013 O3SYM O3ASYM

9. Mean inter-annual NAM variance – Result III dpe - 8 O3SYM control run O3ASYM anomaly run ERA-INTERIM + comparable low-pass variance structure in ECHAM5 model runs and ERA-Interim + significant change (green line, 95 % conf.) in the upper stratosphere for O3* anomaly run SNAP-Reading-25.4.2013

10. Prediction of AO by NAM (p) – Result IV dpe - 9 + less NAM predictability in model runs in comparison to ERA INTERIM reanalysis + improvement of predictability by zonally asymmetric ozone O3* (anomaly run) in the middle stratosphere + significant increase in early winter and midwinter as known from observation SNAP-Reading-25.4.2013

11. Sensitivity study with ECHAM5 – AO – Result V dpe -10 + AO + minimum in mid-1980s, followed by an increase for O3ASYM run SNAP-Reading-25.4.2013 O3ASYM O3SYM ERA-Interim

12. Sensitivity study with ECHAM5 RWB –P2 dpe - 11 + anticyclonic Rossby wave breaking of poleward type P2 difference O3SYM for mean winter (DJF) O3ASYM SNAP-Reading-25.4.2013 + significant change of P2-RWB events over western Europe in O3ASYM during 1980-1999 period due to stronger diffluence of the background field + explanation was given by Peters & Waugh (1995 JAS)

13. Summary & conclusion - model study + found significant changes of stationary wave, of intra-seasonal and interannual variability in the stratosphere which are induced by zonally asymmetric ozone in the stratosphere + further: showed a significant increase of the predictability of surface AO by NAM (p) in midwinter + furthermore: identified significant more poleward Rossby wave breaking events over the NA-EU-region in upper troposphere + conclude that zonally asymmetric ozone heating caused a significant change in the stratospheric and tropospheric circulation, especially it changed the structure of RWB events over the NA-EU region + zonally asymmetric ozone should be considered in the CMIP6 dpe - 12 SNAP-Reading-25.4.2013

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