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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

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VARNAER is a DFG funded project in the frame of the PANDOWAE group

www.pandowae.de

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

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

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Sensitivity study with ECHAM5 - Methods I

Model configuration: + performed two AGCM - ECHAM5-MA runs (for T42, L39, Htop 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 - 4SNAP-Reading-25.4.2013

Structure evolution of decadal zonally asymmetric O3*

Mean O3* at 20 hPa

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+ wave-1 structure in zonally asymmetric ozone + increase and decadal variability in ozone amplitude

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1990s

1960s

ERA-40 Winter (DJF)

Quasi-stationary wave change for January – Result I

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+ 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

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Sensitivity study with ECHAM5 – SSW – Result II

+ number of major SSW events without final

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+ significant increase of major SSW events in 1980/90s for O3ASYM run

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O3SYMO3ASYM

Mean inter-annual NAM variance – Result III

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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

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Prediction of AO by NAM (p) – Result IV

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+ 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

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Sensitivity study with ECHAM5 – AO – Result V

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+ AO+ minimum in mid-1980s, followed by an increase for O3ASYM run

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O3ASYM

O3SYM

ERA-Interim

Sensitivity study with ECHAM5 RWB –P2

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+ anticyclonic Rossby wave breaking of poleward type P2 difference O3SYM for mean winter (DJF) O3ASYM

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+ 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)

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

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