1 interannual variability in stratospheric ozone xun jiang advisor: yuk l. yung department of...
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1
Interannual Variability in Stratospheric Ozone
Xun Jiang Advisor: Yuk L. Yung
Department of Environmental Science and Engineering
California Institute of Technology
11/8/2006
2
Overview
• Ozone: Observations and Models Tropics: QBO, QBO-AB, Solar Cycle, ENSO, MJO High Latitudes: Annular Modes
3
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
4
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.
8
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
15
16
High Latitude IAV of Combined Column O3 in NH
1st
30.4%
Cor. Coeff.
0.53
17
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
19
• 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%
21
Leading Mode in SH
59.5%
Data
Model
43.9%
22
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
24
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.