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Application of the ARGO and TAO data in improving the subsurface entrainment temperature parameterization for the Zebiak-Cane Ocean model Yonghong Yin* Renhe Zhang ， Li Shi ， Tao Niu Chinese Academy of Meteorological Sciences * Email: yinyh@cams.cma.gov.cn

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Outline 1.Introduction 2.Comparison of the Model Results with the Observational Data 3.Assessment of the Parameterizations by using ARGO and TAO/TRITON data 4.Simulation with the new Parameterization 5.Concluding Remarks

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ZC model (or Lamont model): An intermediate coupled ocean-atmosphere model, presented by Zebiak and Cane (1987), has been widely used not only for routinely ENSO forecasting but also for understanding ENSO theory. An intermediate coupled ocean-atmosphere model, presented by Zebiak and Cane (1987), has been widely used not only for routinely ENSO forecasting but also for understanding ENSO theory.

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ocean model: The ocean circulation is governed by adiabatic, linear shallow water dynamics. The ocean circulation is governed by adiabatic, linear shallow water dynamics. The SSTA are calculated from a fully nonlinear surface mixed layer temperature equation. The SSTA are calculated from a fully nonlinear surface mixed layer temperature equation. Thermocline displacement determined by wind forcing affects SST through the subsurface entrainment temperature parameterization. Thermocline displacement determined by wind forcing affects SST through the subsurface entrainment temperature parameterization. The core scheme is the subsurface temperature parameterization. The core scheme is the subsurface temperature parameterization.

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LDEO-2,3,4: Chen et.al. (1995, 1998,2000) During the resent 10 years, the predictability skill of the ZC model has been improved by introducing the initialization/assimilation scheme and statistical model bias correction scheme to the coupled model.

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subsurface temperature P arameterization it describes the relationship between the subsurface temperature anomaly and the thermocline depth anomaly it describes the relationship between the subsurface temperature anomaly and the thermocline depth anomaly Zebiak and Cane (1987), a hyperbolic tangent function h>0h<0

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Y. Chen et al. (1995): based on the regression between the annual cycle in monthly mean subsurface temperature and in the model thermocline perturbations. Y. Chen et al. (1995): based on the regression between the annual cycle in monthly mean subsurface temperature and in the model thermocline perturbations. i.e. based on the climatological data. Dewitte and Perigaud (1996,DP): proposed new parameters to improve the simulation based on the XBT data but the western Pacific region are fewer considered. Wang (1999): meridional structure in the western Pacific. Wang (1999): meridional structure in the western Pacific. no compared with enough observational data no compared with enough observational data Kang and Kug (2000): based on the SVD singular vectors from the NCEP ocean assimilation data. ……

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Motivation of this work : The evaluation of the model parameterization by high resolution in situ data, such as ARGO and TAO array, should be more interesting and significant, especially for the western Pacific. The evaluation of the model parameterization by high resolution in situ data, such as ARGO and TAO array, should be more interesting and significant, especially for the western Pacific.

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Data : Argo: Jan 2001 - Dec 2003 Argo: Jan 2001 - Dec 2003 TAO/TRITON: Mar 1980 - Dec 2003 WOA01: Climatological data WOA01: Climatological data NCEP/NCAR reanalysis (Kalnay et al. 1996): wind stress NCEP OISST.V2 (Reynolds et al. 2002): SSTA NCEP OISST.V2 (Reynolds et al. 2002): SSTA NCEP Pacific Analysis (Behringer et al., 1998): Subsurface Temperature Anomaly Carton et al. (2000): 20 C isotherm depth data Carton et al. (2000): 20 C isotherm depth data Anomalies are computed based on the monthly mean over the period Jan 1982 - Dec 2003. Anomalies are computed based on the monthly mean over the period Jan 1982 - Dec 2003.

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Comparison of the Model Results with the Observational Data: thermocline depth anomalies (TDA, Unit: m) Nino1+2: 90 -80 W, 10 S-EQ Nino3: 150 -90 W, 5 S-5 N Model, Carton, TAO

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Comparison of the Model Results with the Observational Data: thermocline depth anomalies (TDA, Unit: m ) Nino4: 160 E-150 W, 5 S-5 N WP: 130 -160 E, 0-10 N Model, Carton, TAO The interannual variability of simulated TDA are considerably consistent with the observations both in the eastern and western Pacific.

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Comparison of the Model Results with the Observational Data: sea surface temperature anomalies (SSTA, Unit: C) sea surface temperature anomalies (SSTA, Unit: C) Nino1+2: 90 -80 W, 10 S-EQ Nino3: 150 -90 W, 5 S-5 N Model, OISST.v2

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Comparison of the Model Results with the Observational Data: sea surface temperature anomalies (SSTA, Unit: C) sea surface temperature anomalies (SSTA, Unit: C) Model, OISST.v2 Nino4: 160 E-150 W, 5 S-5 N WP: 130 -160 E, 0-10 N It shows the model equatorial SSTA from the eastern to central regions coincide quite well with the observations except in the tropical western Pacific, where the model can not simulate the observed interannual variability.

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Comparison of the Model Results with the Observational Data: subsurface temperature anomalies (STA, Unit: C) subsurface temperature anomalies (STA, Unit: C) Nino1+2: 90 -80 W, 10 S-EQ Nino3: 150 -90 W, 5 S-5 N Model, NCEP, TAO

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Comparison of the Model Results with the Observational Data: subsurface temperature anomalies (STA, Unit: C) subsurface temperature anomalies (STA, Unit: C) Nino4: 160 E-150 W, 5 S-5 N WP: 130 -160 E, 0-10 N Model, NCEP, TAO It is indicated that in Nino4 and WP regions, STA is too weak compared with the observations. So the model deficiency may be caused, to some extent, by a poor subsurface temperature parameterization in the equatorial central-western Pacific.

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Comparison of the Model Results with the Observational Data: subsurface temperature anomalies (STA, Unit: C) subsurface temperature anomalies (STA, Unit: C) Nino1+2: 90 -80 W, 10 S-EQ Nino3: 150 -90 W, 5 S-5 N New Scheme, ZC Scheme, NCEP, TAO

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Comparison of the Model Results with the Observational Data: subsurface temperature anomalies (STA, Unit: C) subsurface temperature anomalies (STA, Unit: C) Nino4: 160 E-150 W, 5 S-5 N WP: 130 -160 E, 0-10 N New Scheme, ZC Scheme, NCEP, TAO

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Comparison of the Model Results with the Observational Data: sea surface temperature anomalies (SSTA, Unit: C) sea surface temperature anomalies (SSTA, Unit: C) Nino1+2: 90 -80 W, 10 S-EQ Nino3: 150 -90 W, 5 S-5 N New Scheme, ZC Scheme, OISST.v2

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Comparison of the Model Results with the Observational Data: sea surface temperature anomalies (SSTA, Unit: C) sea surface temperature anomalies (SSTA, Unit: C) New Scheme, ZC Scheme, OISST.v2 Nino4: 160 E-150 W, 5 S-5 N WP: 130 -160 E, 0-10 N New Scheme, ZC Scheme, OISST.v2

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SST anomalies averaged over 5 S-5 N.

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Correlation coefficients of SSTA between observations and simulations with new parameterization (upper) and with the original ZC scheme (bottom) for the period 1982-2003.

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Summary To assess the model parameterization scheme, the relationships of subsurface temperature and the thermocline depth in different areas are checked by using ARGO and TAO data. It shows the parameterized subsurface temperature anomalies are somewhat too strong for Nino1+2 regions, closely fitting for Nino3 region, and too weak for Nino4-WP regions. The amount of ARGO data in the Nino1+2 regions are too little and there is no TAO data, therefore, it needs more observation in this area.

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Summary Compared with the original ZC scheme and the scheme of Dewitte and Perigaud (1996), the new scheme can better describe the relationship between the subsurface temperature anomaly and the thermocline depth anomaly in the tropical Pacific Ocean. It is also shown that the model with the new scheme can better simulate the subsurface temperature and SSTA in the equatorial western Pacific.

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Thanks

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