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Interannual Variability in Stratospheric Ozone

Xun Jiang Advisor: Yuk L. Yung

Department of Environmental Science and Engineering

California Institute of Technology

11/8/2006

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Overview

• Ozone: Observations and Models Tropics: QBO, QBO-AB, Solar Cycle, ENSO, MJO High Latitudes: Annular Modes

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Data and Models

• Data Merged O3 Data (MOD) [McPeters et al., 1996]

Assimilated O3 from European Centre for Medium-Range Weather Forecasts (ECMWF) [Uppala et al., 2005]

• Models 2-D Caltech/JPL Chemistry and Transport Model 2-D Interactive Chemistry and Transport Model

3-D GEOS-4 Chemistry-Climate Model

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Principal Component Analysis (PCA)

(N timesteps M stations ) Covariance Matrix ( M M )

X

eXp

EOFs ( e, Eigenvectors of C ): modes of spatial pattern

PCs (p, ): time-dependent amplitudes of the EOFs

Eigenvalue: the fraction of variance captured by each EOF

The original data can be represented by

To make EOF patterns have dimensional units. We multiply each EOF by the square root of their associated eigenvalue, and divide each PC by this value.

TT EEXXN

C

1

1

k

Tkk etpX ),()(

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Tropical IAV in the Column Ozone from MOD[Camp et al., 2003]

EOFs

PCs Amplitude Spectra

42%

Cumul. Var.

QBO

Decadal

R=0.80

6

42%

75%

90%

EOFs PCs Amplitude SpectraCumul. Var.

Tropical IAV in the Column Ozone from MOD[Camp et al., 2003]

93%

R=0.80

R=0.73

R=0.71

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Tropical IAV in the Column Ozone from Model[Jiang et al., 2004]

• Mean meridional circulation and eddy mixing coefficients derived from the NCEP/DOE Reanalysis 2 (NCEP2).

• The first realistic simulation of the QBO and QBO-Annual Beat (QBO-AB) in column ozone from 1979 to 2002.

• The model ozone results for QBO and QBO-AB are compared to the signals obtained by the zonal mean MOD observations.

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MOD

2D CTM

Composite of Column Ozone from 1979 to 2002

Tropical IAV in the Column Ozone from Model[Jiang et al., 2004]

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Tropical IAV in the Column Ozone from Model[Jiang et al., 2004]

Latitude distribution of ozone anomaly

MOD

2D CTM

DU

DU

10

74%

EOFs PCs Power Spectra Cumul.

Var.

85%

Ozone PCA: 2D CTM and Zonal MOD [Jiang et al., 2004]

Tropical IAV in the Column Ozone from Model

QBO-AB

QBO

Model (Solid) & MOD (Dash)

R=0.87

R=0.5

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Quasi-biennial Oscillation-Annual Beat of Ozone

[Jiang et al., 2005]

• An idealized 2-D chemistry and transport model is used to investigate the spatial patterns and propagation the QBO-annual beat (QBO-AB) signal in ozone in the tropics and subtropics

• An extended EOF analysis is used to study the propagation of QBO and QBO-AB. The model results are compared to those from the Merged Ozone Data (MOD).

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I: Model: Fully interactive model Comprehensive treatment of stratospheric chemistry The QBO is produced by the parameterization for the

deposition of Kelvin and Rossby-gravity wave momentum in the tropical zonal wind.

II: Merged Ozone Volume Mixing Ratio Data

Model Description and Data

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Propagation of QBO and QBO-AB (Model)

PC1EEOF1+ PC2EEOF2

at equator

PC3EEOF3+ PC4EEOF4

at 12.5 N

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Propagation of QBO and QBO-AB (Data)

PC1EEOF1+ PC2EEOF2

at equator

PC3EEOF3+ PC4EEOF4

at 12.5 N

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High Latitude IAV of Combined Column O3 in NH

1st

30.4%

Cor. Coeff.

0.53

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3.5-year Signal in the Arosa Ozone

• Arosa (46N, 9E) column ozone time series (Aug. 1931 ~ Dec. 2002)

• Signals in Spectra: 3.5 years, QBO-AB, QBO

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1st

High Latitude IAV of Combined Column O3 in SH

43.9%

Cor. Coeff.

0.45

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• Model

Chemistry module on-line in the general circulation model [Douglass et al., 2003; Stolarski et al., 2006a; Bloom et al., 2005]

Sea surface temperature and sea ice are from observations

No solar cycle, volcanic aerosol, and QBO in the model.

• Leading modes for the model O3 in the two hemispheres

• ENSO signals in TOMS and model O3

Comparison with a 3-D Chemistry-Climate Model

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Leading Mode in NH

31.8%

Data

Model

30.4%

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Leading Mode in SH

59.5%

Data

Model

43.9%

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ENSO in TOMS and 3-D Chemistry-Climate Model

TOMS

Model

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PC timeseries of O3 in Tropics

Cor. Coeff.

0.76TOMS

Model 0.53

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MJO in GEOS-chem Model

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MJO in GEOS-chem Model

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Conclusions

• The 2-D CTM provides realistic simulations of the IAV of ozone in the tropics. The QBO and QBO-Annual Beat are well captured in the Catech/JPL model.

• An extended EOF analysis reveals the characteristic pattern of the downward propagation of QBO and upward propagation of QBO-AB, which is simulated well by a 2-D interactive CTM.

• In the high latitudes, first modes are nearly zonally symmetric and represent the connections to the Annular Modes and the Quasi-Biennial Oscillation.

• 3-D GEOS-4 chemistry-climate model can simulate the ozone trend reasonably well in both hemispheres. Model cannot simulate the low-frequency oscillations well.

• 3-D Model captures ENSO signal well in the tropics. Some discrepancies for the model ENSO signal in the SH.