c. timmreck, m. thomas, m. giorgetta, m. esch, h.-f. graf 1 , h. haak,
DESCRIPTION
Interactions between volcanic eruptions and El Ni ñ o: Studies with a coupled atmosphere-ocean model. C. Timmreck, M. Thomas, M. Giorgetta, M. Esch, H.-F. Graf 1 , H. Haak, J. Jungclaus, W. Müller, E. Roeckner , H. Schmidt and G. Stenchikov 2 Max Planck Institute for Meteorology, Hamburg - PowerPoint PPT PresentationTRANSCRIPT
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Interactions between volcanic eruptions and El Niño: Studies with a
coupled atmosphere-ocean modelC. Timmreck, M. Thomas, M. Giorgetta, M. Esch, H.-F. Graf1, H. Haak,
J. Jungclaus, W. Müller, E. Roeckner, H. Schmidt and G. Stenchikov2
Max Planck Institute for Meteorology, Hamburg
1Centre Atmospheric Sciences University, Cambridge 2Rutgers-The State University of NJ, New Brunswick
AGU Spring meeting 2007
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o
The last three biggest eruptions (Agung (1963), El Chichón (1982) and Pinatubo (1991)) occurred at the time as an El Niño event.
Dynamic response due to the combined effects of El Niño and volcanic eruptions are still uncertain.
Paleo reconstructions (Adams et al, 2003) show that large volcanic eruptions enhance the probability of an El Niño event.
AOGCMs are an important tool to improve our understanding of the atmospheric and oceanic response to the combined effects of El Niño and large volcanic eruptions.
Coupled El Niño Volcanic runs
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Coupled El Niño Volcanic runs
We have carried out a series of volcanic simulations with the AOGCM, ECHAM5/MPIOM.
The volcanic radiative forcing is calculated online in the model. A realistic spatial-temporal distribution of aerosol optical parameters for the Pinatubo episode is used.
Optical depth in the visible
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Niño 3.4 SST anomalies in ECHAM5/MPIOM
The frequency analysis of the El Niño events show good agreement with observations. However, the amplitude of 1.7 K is higher than in the IPCC runs (1.5 K) and in the AMIP cases (1.K)
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Three different cases are selected from a 100 year control run.
5 ensembles for Jan and June, perturbed / unperturbed.
Each ensemble run has been performed for two years.
Coupled El Niño Volcanic runsNiño 3.4 Case I Niño 3.4 Case IIINiño 3.4 Case II
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Stratospheric temperature response [K]
ERA 40 Reanalysis Case I June
30 hPa
100 hPa
50 hPa
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Temperature response at 50 hPa
Case I June
Case II June
Case III June
Case II January
Case I January
Case III January
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GPH Anomaly 50 hPa DJF „91/92“
Era 40 Reanalysis
Case I JuneCase I January
Case II January
Case II June
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2m temperature anomaly [k] DJF „91/92“
Era 40 Reanalysis
Case I January Case I June
Case II JuneCase II January
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Case II June 2m temp. anomalies [K] DJF 91/92
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Atmospheric response
The stratospheric tropical temperature response is similar for all cases and in agreement with observations.
The dynamical response in the NH high latitudes is highly variable. Only in a few cases the observed pattern is mirrored. However, some ensemble members reflect the observed pattern.
Further analysis (EP fluxes, refractive indices) is necessary
Note: model top at 10 hPa !
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January
June
Niño 3.4 Case III CTRL
Niño 3.4 SST anomalies [k] Case III
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Niño 3.4 SST anomalies [k] Case II
January
June
Niño 3.4 Case II CTRL
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Niño 3.4 SST anomalies [k] Case I
Niño 3.4 Case I CTRL
January
June
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U10 [m/s]+ 4
- 4
+ 2
- 2
0
Ocean T 6 m [K]
Hovmoeller diagram of anomalies 5N-5SCase I June
Ocean T 100 m [K]
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Oceanic response
Large interannual variability can be detected in the tropical dynamical ocean heat response.
Significant ocean response only in two cases: Case I June
where the model is triggered into a La Niña state. Ekman pumping in the mid equatorial Pacific leads to significant cooling in the perturbed model run.
Case II January
where radiative effects damp the El Niño signal
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Conclusion I
Based on our model results we cannot support the hypothesis from Adams et al.(2003) that volcanic eruptions enhance the possibilty of an El Niño event.
The dynamical response in the atmosphere and in the ocean is highly variable and differs between the selected cases, but also quite strongly between the single ensemble members.
Further analysis is necessary to learn more about
the physical mechanisms behind and why the ensemble members behave differently
Ongoing work
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Conclusion II
Thank you very muchfor your attention!
We had some questions before we started.
Now we have even more.
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Coupled El Niño Volcanic runs
Oceanic response
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Temperature differences (K) and respective significances in the equatorial pacific. The grey scale indicates significances of 90, 95, and 99%.
Oce
an d
epth
(m
)
199201, 7 months after eruption
Oce
an d
epth
(m
)Temperature response in the equatorial Pacific
Case I June
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Nino 82/83
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Nino 91792
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Coupled El Niño Volcanic runs
Atmospheric response
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Case I June 2m temp. anomalies
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Case I June GPH anomalies at 50 hPa
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Case II June 2m temp. anomalies
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Case II June GPH anomalies at 50 hPa