• Arakawa, A., 1972: Design of the UCLA general circulation model. Numerical simulation of weather and climate. Dept. of Meteorology, University of California, Report 7, 116 pp.

  • Asselin, R., 1972: Frequency filter for time integration. Mon. Wea. Rev.,100, 487–490.

  • Battisti, D. S., 1988: The dynamics and thermodynamics of a warm event in a coupled atmosphere/ocean model. J. Atmos. Sci.,45, 2889–2919.

  • ——, and A. C. Hirst, 1989: Interannual variability in a tropical atmosphere–ocean model: Influence of the basic state, ocean geometry and nonlinearity. J. Atmos. Sci.,46, 1687–1712.

  • Barnett, T. P., N. Graham, M. Cane, S. Zebiak, S. Dolan, J. O’Brien, and D. Legler, 1988: On the prediction of El Niño of 1986–1987. Science,241, 192–196.

  • Blanke, B., and P. Delecluse, 1993: Variability of the tropical Atlantic Ocean simulated by a general circulation model with two different mixed-layer physics. J. Phys. Oceanogr.,23, 1363–1388.

  • Blumenthal, M. B., and M. A. Cane, 1989: Accounting for parameter uncertainties in model verification: An illustration with tropical sea surface temperature. J. Phys. Oceanogr.,19, 815–830.

  • Boulanger, J.-P., and C. Menkes, 1995: Propagation and reflection of long equatorial waves in the Pacific Ocean during the 1992–1993 El Niño. J. Geophys. Res.,100, 25 041–25 059.

  • ——, and L.-L. Fu, 1996: Evidence of boundary reflection of Kelvin and first-mode Rossby waves from TOPEX/Poseidon sea level data. J. Geophys. Res.,101, 16 361–16 371.

  • ——, P. Delecluse, C. Maes, and C. Levy, 1997: Long equatorial waves in a high-resolution OGCM simulation of the tropical Pacific Ocean during the 1985–1994 TOGA period. Mon. Wea. Rev.,125, 972–984.

  • Busalacchi, A. J., and M. A. Cane, 1985: Hindcasts of sea level variations during the 1982–1983 El Niño. J. Phys. Oceanogr.,15, 213–221.

  • ——, and ——, 1988: The effect of varying stratification on low-frequency equatorial motions. J. Phys. Oceanogr.,18, 801–812.

  • Cane, M. A., 1984: Modeling sea level during El Nino. J. Phys. Oceanogr.,14, 1864–1874.

  • ——, and E. S. Sarachik, 1981: The response of a linear baroclinic equatorial ocean to periodic forcing. J. Mar. Res.,39, 651–693.

  • ——, and Y. du Penhoat, 1982: On the effects of islands on low frequency equatorial motions. J. Mar. Res.,40, 937–962.

  • ——, and R. J. Patton, 1984: A numerical model for low frequency equatorial dynamics. J. Phys. Oceanogr.,14, 1853–1863.

  • ——, S. E. Zebiak, and S. C. Dolan, 1986: Experimental forecasts of El Niño. Nature,321, 827–832.

  • Chen, Y.-Q., D. S. Battisti, and E. S. Sarachik, 1995: A new ocean model for studying the tropical oceanic aspects of ENSO. J. Phys. Oceanogr.,25, 2065–2089.

  • Clarke, A. J., 1991: On the reflection and transmission of low-frequency energy at the irregular western Pacific Ocean boundary. J. Geophys. Res.,96, 3289–3305.

  • Davis, R. E., 1977: Techniques for statistical analysis and prediction of geophysical fluid systems. Geophys. Astrophys. Fluid. Dyn.,8, 245–277.

  • Déqué, M., C. Dreveton, A. Braun, and D. Cariolle, 1994: The ARPEGE/IFS atmosphere model: A contribution to the French community climate modelling. Climate Dyn.,10, 249–266.

  • Delcroix, T., J. Picaut, and G. Eldin, 1991: Equatorial Kelvin and Rossby waves evidenced in the Pacific Ocean through Geosat sea level and surface currents anomalies. J. Geophys. Res.,96, 3249–3262.

  • Delecluse, P., G. Madec, M. Imbard, and C. Levy, 1993: OPA version 7 ocean general circulation model reference manual. Rapport Interne LODYC 93/05, 111 pp. [Available from Tour 14, 4, Place Jussieu 75252, Paris Cedex 5, France.].

  • Du Penhoat, Y., and M. A. Cane, 1991: Effects of low-lattitude western boundary gaps on the reflection of equatorial motions. J. Geophys. Res.,96, 3307–3322.

  • ——, ——, and R. J. Patton, 1983: Reflections of low frequency equatorial waves on partial boundaries. Hydrodynamics of the Equatorial Ocean, J. C. L. Nihoul, Ed., Elsevier, 237–358.

  • Eriksen, C. C., 1985: Moored observations of deep low-frequency motions in the central Pacific: Vertical structure and interpretation as equatorial waves. J. Phys. Oceanogr.,15, 1085–1113.

  • ——, 1988: On wind forcing and observed oceanic wave number spectra. J. Geophys. Res.,93, 4985–4992.

  • Fjelstad, J. E., 1933: Interne Wellen. Geofys. Publ.,10 (6), 35 pp.

  • Fukumori, I., R. Raghunath, and L.-L. Fu, 1998: Nature of global large-scale sea level variability in relation to atmospheric forcing: A modeling study. J. Geophys. Res.,103, 5493–5512.

  • Gent, R. G., K. O’Neill, and M. A. Cane, 1983: A model of the semiannual oscillation in the equatorial Indian Ocean. J. Phys. Oceanogr.,13, 2148–2160.

  • Giese, B. S., 1989: Equatorial oceanic response to forcing on time scales from days to months. NOAA Tech. Memo. ERL PMEL-87, 104 pp.

  • ——, and D. E. Harrison, 1990: Aspect of the Kelvin wave response to episodic wind forcing. J. Geophys. Res.,95, 7289–7312.

  • Gill, A. E., 1982: Changes in thermal structure of the equatorial Pacific during the 1972 El Niño as revealed by bathythermograph observations. J. Phys. Oceanogr.,12, 1373–1387.

  • ——, 1983: An estimate of sea-level and surface-current anomalies during the 1972 El Niño and consequent thermal effects. J. Phys. Oceanogr.,13, 586–606.

  • Graham, N. E., and W. B. White, 1988: The El Niño/Southern Oscillation as a natural oscillator of the tropical Pacific Ocean–atmosphere system. Science,240, 1293–1302.

  • Jerlov, N. G., Ed., 1968: Optical Oceanography. Elsevier, 194 pp.

  • Jiang N., J. D. Neelin, and M. Ghil, 1995: Quasi-quadriennial and quasi-biennial variability in the equatorial Pacific. Climate Dyn.,12, 101–112.

  • Kessler, W. S., and J. P. McCreary, 1993: The annual wind-driven Rossby wave in the subthermocline equatorial Pacific. J. Phys. Oceanogr.,23, 1192–1207.

  • Kleeman, R., A. M. Moore, and N. R. Smith, 1995: Assimilation of subsurface thermal data into an intermediate tropical coupled ocean–atmosphere model. Mon. Wea. Rev.,123, 3103–3113.

  • Kutzbach, J. E., 1967: Empirical eigenvectors of sea level pressure, surface temperature and precipitating complexes over North America. J. Appl. Meteor.,6, 791–802.

  • Lau, K.-H., and N.-C. Lau, 1990: Observed structure and propagation characteristics of tropical summertime synoptic scale disturbances. Mon. Wea. Rev.,118, 1888–1913.

  • Levitus, S., 1982: Climatological Atlas of the World Ocean. NOAA Prof. Paper No. 13, U.S. Govt. Printing Office, 173 pp.

  • Lighthill, M. J., 1969: Dynamical response of the Indian Ocean to onset of the southwest monsoon. Philos. Trans. Roy. Soc. London, Ser. A,265, 45–92.

  • Lukas, R., and E. Firing, 1985: The annual Rossby wave in the central equatorial Pacific Ocean. J. Phys. Oceanogr.,15, 55–67.

  • Maes, C., 1996: Equilibre du réservoir chaud de l’océan Pacifique tropical ouest. Ph.D. thesis, Université Pierre et Marie Curie, Paris VI, France, 232 pp.

  • ——, G. Madec, and P. Delecluse, 1997: Sensitivity of an equatorial Pacific OGCM to lateral diffusion. Mon. Wea. Rev.,125, 958–971.

  • Marti, O., G. Madec, and P. Delecluse, 1992: Comment on “Net diffusivity in ocean circulation models with nonuniform grids” by F. L. Yin and I. Y. Fung. J. Geophys. Res.,97, 12 763–12 766.

  • McCreary, J. P., 1984: Equatorial beams. J. Mar. Res.,42, 395–430.

  • McPhaden, M. J., J. A. Proehl, and L. M. Rothstein, 1986: The interaction of equatorial Kelvin waves with realistically sheared zonal currents. J. Phys. Oceanogr.,16, 1499–1515.

  • Meyers, G., 1979: Annual variation in the slope of the 14°C isotherm along the equator in the Pacific Ocean. J. Phys. Oceanogr.,9, 885–891.

  • Millero, F. S., and A. Poisson, 1981: An international one-atmosphere equation of state of sea water. Deep-Sea Res.,28A, 625–629.

  • Oberhuber, J. M., 1988: An atlas based on the COADS data set: The budgets of heat, buoyancy and turbulent kinetic energy at the surface of the global ocean. Report No. 15, Max-Planck-Institut für Meteorologie, 20 pp. [Available from Max-Planck-Institut für Meteorologie, Bundesstr. 55, D-20146 Hamburg, Germany.].

  • Paulson, C. A., and J. J. Simpson, 1977: Irradiance measurements in the upper Ocean. J. Phys. Oceanogr.,7, 952–956.

  • Périgaud, C., and B. Dewitte, 1995: El Niño–La Niña events simulated with Cane and Zebiak’s model and observed with satellite or in situ data. Proc. TOGA 95 Meeting, Vol II, Melbourne, Victoria, Australia, 615–619.

  • ——, and ——, 1996: El Niño–La Niña events simulated with Cane and Zebiak’s model and observed with satellite or in situ data. Part I: Model data comparison. J. Climate,9, 65–84.

  • ——, S. E. Zebiak, F. Mélin, J.-P. Boulanger, and B. Dewitte, 1997:On the role of meridional wind anomalies in a coupled model of ENSO. J. Climate,10, 761–773.

  • Picaut, J., and L. Sombardier, 1993: Influence of density stratification and bottom depth on vertical mode structure functions in the tropical Pacific. J. Geophys. Res.,98, 14 727–14 737.

  • ——, F. Masia, and Y. DuPenhoat, 1997: An advective–reflective conceptual model for the oscillatory nature of ENSO. Science,277, 663–666.

  • Reverdin, G., C. Frankignoul, E. Kestenare, and M. J. McPhaden, 1994: Seasonal variability in the surface currents of the equatorial Pacific. J. Geophys. Res.,99, 20 323–20 344.

  • ——, A. Kaplan, and M. Cane, 1996: Sea level from temperature profiles in the Tropical Pacific Ocean 1975–1992. J. Geophys. Res.,101, 18 105–18 119.

  • Reynolds, R. W., and T. M. Smith, 1994: Improved global sea surface temperature analyses using optimum interpolation. J. Climate,7, 929–948.

  • Robertson, A. W., C.-C. Ma, C. R. Mechoso, and M. Ghil, 1995a: Simulation of the tropical Pacific climate with a coupled ocean–atmosphere general circulation model. Part I: The seasonal cycle. J. Climate,8, 1178–1198.

  • ——, ——, M. Ghil, and C. R. Mechoso, 1995b: Simulation of the tropical Pacific climate with a coupled ocean–atmosphere general circulation model. Part II: Interannual variability. J. Climate,8, 1199–1216.

  • Schopf, P. S., and M. J. Suarez, 1988: Vacillations in a coupled ocean–atmosphere model. J. Atmos. Sci.,45, 549–566.

  • Vautard, R., and M. Ghil, 1989: Singular spectrum analysis in nonlinear dynamics, with applications to paleoclimatic time series. Physica D,35, 395–424.

  • Vialard, J., and P. Delecluse, 1998: An OGCM study for the TOGA decade. Part II: Barrier-layer formation and variability. J. Phys. Oceanogr.,28, 1089–1106.

  • Vintzileos, A., 1996: Etude de la variabilité climatique avec un modèle couplé atmosphère globale-océan Pacifique tropical. Ph.D. thesis, Université Pierre et Marie Curie, Paris VI, France, 178 pp. [Available from 4 Place Jussieu 75252, Paris Cedex 5, France.].

  • Weare, B. C., and J. S. Nasstrom, 1982: Examples of extended emperical orthogonal function analysis. Mon. Wea. Rev.,110, 481–485.

  • Zebiak, S. E., and M. A. Cane, 1987: A model El Niño–Southern Oscillation. Mon. Wea. Rev.,115, 2262–2278.

  • ——, and ——, 1991: Greenhouse-Gas-Induced Climate Change: A Critical Appraisal of Simulations and Observations. Elsevier Science, 457–569.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 216 44 3
PDF Downloads 90 32 4

Vertical Structure of an OGCM Simulation of the Equatorial Pacific Ocean in 1985–94

View More View Less
  • 1 LEGOS/UMR5566/CNES, Toulouse, France
Restricted access

Abstract

The vertical structure of the variability in the equatorial Pacific in a high-resolution ocean general circulation model (OGCM) simulation for 1985–94 is investigated. Near the equator the linear vertical modes are estimated at each grid point and time step of the OGCM simulation. The characteristics of the vertical modes are found to vary more in space than in time. The contribution of baroclinic modes to surface zonal current and sea level anomalies is analyzed. The first two modes contribute with comparable amplitude but with different spatial distribution in the equatorial waveguide. The third and fourth modes exhibit peaks in variability in the east and in the westernmost part of the basin where the largest zonal gradients in the density field and in the vertical mode characteristics are found. Higher-order mode (sum of third to the eighth mode) variability is the largest near the date line close to the maximum in zonal wind stress variability. Kelvin and first-meridional Rossby components are derived for each of the first three baroclinic contributions by projection onto the associated meridional structures. They are compared to equivalent ones in multimode linear simulations done with the projection coefficients and phase speeds derived from the OGCM simulation. This suggests that in addition to the first-mode-forced equatorial Kelvin and Rossby waves earlier found in the data, forced waves of higher vertical modes should also be observable. For the first two vertical modes, the anomalies in the linear and the OGCM simulations have a similar magnitude and usually present similar propagation characteristics. Phase speed characteristics are however different in the eastern Pacific with larger values for the OGCM. The effect of zonal changes in the stratification is tested in the linear model for a stratification change located either in the eastern or in the western Pacific. This results in a significant redistribution of energy to higher modes via modal dispersion. In particular the third mode increases to a magnitude closer to the one in the OGCM simulation. Gravest modes are also affected. This suggests that modal dispersion plays an important role and should be considered when interpreting data as a combination of linear long equatorial waves.

Corresponding author address: Dr. Boris Dewitte, LEGOS/UMR 5566/CNES, 14, Ave. Edouard Belin, 31401 Toulouse, Cedex 4, France.

Email: bxd@pontos.cst.cnes.fr

Abstract

The vertical structure of the variability in the equatorial Pacific in a high-resolution ocean general circulation model (OGCM) simulation for 1985–94 is investigated. Near the equator the linear vertical modes are estimated at each grid point and time step of the OGCM simulation. The characteristics of the vertical modes are found to vary more in space than in time. The contribution of baroclinic modes to surface zonal current and sea level anomalies is analyzed. The first two modes contribute with comparable amplitude but with different spatial distribution in the equatorial waveguide. The third and fourth modes exhibit peaks in variability in the east and in the westernmost part of the basin where the largest zonal gradients in the density field and in the vertical mode characteristics are found. Higher-order mode (sum of third to the eighth mode) variability is the largest near the date line close to the maximum in zonal wind stress variability. Kelvin and first-meridional Rossby components are derived for each of the first three baroclinic contributions by projection onto the associated meridional structures. They are compared to equivalent ones in multimode linear simulations done with the projection coefficients and phase speeds derived from the OGCM simulation. This suggests that in addition to the first-mode-forced equatorial Kelvin and Rossby waves earlier found in the data, forced waves of higher vertical modes should also be observable. For the first two vertical modes, the anomalies in the linear and the OGCM simulations have a similar magnitude and usually present similar propagation characteristics. Phase speed characteristics are however different in the eastern Pacific with larger values for the OGCM. The effect of zonal changes in the stratification is tested in the linear model for a stratification change located either in the eastern or in the western Pacific. This results in a significant redistribution of energy to higher modes via modal dispersion. In particular the third mode increases to a magnitude closer to the one in the OGCM simulation. Gravest modes are also affected. This suggests that modal dispersion plays an important role and should be considered when interpreting data as a combination of linear long equatorial waves.

Corresponding author address: Dr. Boris Dewitte, LEGOS/UMR 5566/CNES, 14, Ave. Edouard Belin, 31401 Toulouse, Cedex 4, France.

Email: bxd@pontos.cst.cnes.fr

Save