Abstract
During Tropical Ocean and Global Atmosphere (TOGA)/Coupled Ocean and Atmosphere Research Experiment (COARE) Intensive Observing Period (IOP), upward-looking acoustic Doppler current profilers (ADCP) and current meters were moored at two equatorial sites (147°E and 154°E) and two off-equatorial sites (2°N and 2°S, 156°E) in the warm pool region of the western equatorial Pacific. Using current data obtained by these moorings, we have shown that there is a dominant signal with a period of about 2 days from the end of November to the middle of December in 1992, except at the equatorial site on 147°E (Ueki et al., 1998). The energy of this quasi-2-day signal for the meridional current is larger than that for the zonal one and the signal has a high coherence between two off-equatorial sites. In this paper, using band-passed time series of the meridional curerent, we investigated characters of the quasi-2-day signal and attempted to interpret this signal as an equatorially trapped wave. Complex empirical orthogonal function (CEOF) analysis reveals two different phase propagating features between the equatorial and off-equatorial site. One is an upward propagating signal, which is dominant near the surface at two off-equatorial sites, and the other is a downward propagating signal, which is dominant near 200 m at the equatorial site. If one interprets the quasi-2-day signal as an equatorially trapped wave, it is suggested that it cannot be explained as a single wave but can be described as the superimposition of several wave signals. The main part of these signals consists of two signals, one caused by a meteorological forcing and another by another factor in the ocean field.
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References
Barnett, T. P. (1983): Interaction of the Monsoon and Pacific trade wind system at interanual time scales, Part I, The equatorial zone. Mon. Wea. Rev., 111, 756–773.
Hendon, H. H. and B. Liebmann (1994): Organization of convection within the Madden-Julian oscillation. J. Geophys. Res., 99, 8073–8083.
Kessler, S. W. and J. P. McCreary (1992): The annual wind-driven Rossby wave in the subthermocline equatorial Pacific. J. Phys. Oceanogr., 23, 1192–1207
Kutsuwada, K. and H. Inaba (1995): Year-Long Measurements of upper-ocean currents in the western equatorial Pacific by Acoustic Doppler Current Profilers. J. Meteor. Soc. Japan, 73–2B, 665–675.
Lau, K. M., T. Nakazawa and C.-H. Sui (1991): Observations of cloud cluster hierarchies over the tropical western Pacific. J. Geophys. Res., 96, 3197–3208.
Lukas, R. and E. Firing (1985): The annual Rossby wave in the central equatorial Pacific Ocean. J. Phys. Oceanogr., 11, 55–67.
Lukas, R., P.J. Webster, M. Ji and A. Leetmaa (1995): The large-scale context for the TOGA Coupled Ocean-Atmosphere Response Experiment. Meteorol. Atmos. Phys., 56, 3–16.
Luther, D. S. (1980): Observations of long period waves in the tropical oceans and atmosphere. Tech. Rep, WHOI–80–17, Woods Hole Oceanogr. Inst., Woods Hole, Mass.
Maruyama, T. (1994): Upward transport of westerly momentum due to disturbances of the equatorial lower stratosphere in the period range about 2 days—A Singapore data analysis for 1983–1993. J. Meteor. Soc. Japan, 72, 423–432.
Matsuno, T. (1966): Quasi-geostrophic motions in the equatorial area. J. Meteor. Soc. Japan, 44, 25–43.
McPhaden, M. J. (1993): TOGA-TAO and the 1991–1993 El Niño-Southern Oscillation event. Oceanography, 6, 36–44.
McPhaden, M. J. and R. A. Knox (1979): Equatorial Kelvin and Inertio-Gravity waves in zonal shear flow. J. Phys. Oceanogr., 9, 263–277.
McPhaden, M. J., A. J. Busalacchi, R. Cheney, J. R. Donguy, K. S. Gage, D. Halpern, M. Ji, P. Julian, G. Meyers, G. T. Mitchum, P. P. Niiler, J. Picaut, R. W. Reynolds, N. Smith and K. Takeuchi (1998): The Tropical Ocean-Global Atmosphere observing system: A decade of progress. J. Geophys. Res., 103, 14169–14240.
Murakami, M. (1979): Large-scale aspects of deep convective activity over the GATE area. Mon. Wea. Rev., 107, 994–1013.
Nakazawa, T. (1988): Tropical super clusters within intraseasonal variation over the western Pacific. J. Meteor. Soc. Japan, 66, 823–839.
Philander, S. G. H. (1990): El Niño, La Niña and the Southern Oscillation. Academic Press, 293 pp.
Ripa, P. and S. P. Hayes (1981): Evidence for equatorial trapped waves at the Galapagos Islands. J. Geophys. Res., 86, 6509–6516.
Sato, K., F. Hasegawa and I. Hirota (1994): Short-period disturbances in the equatorial lower stratosphere. J. Meteor. Soc. Japan, 72, 859–872.
Suzuki, T., S. Ito, K. Takeuchi and H. Otobe (1995): Variability of the upper ocean at the equator, 156°E, observed by R/V Hakuho-Maru during TOGA-COARE IOP. J. Meteor. Soc. Japan, 73–2B, 645–652.
Takayabu, Y. N. (1994): Large-scale cloud disturbances associated with equatorial waves. Part II: Westward-propagating inertio-gravity waves. J. Meteor. Soc. Japan, 72, 451–465.
Takayabu, Y. N., K.-M. Lau and C.-H. Sui (1996): Observation of a quasi-2-day wave during TOGA COARE. Mon. Wea. Rev., 124, 1892–1913.
Ueki, I., K. Kutsuwada, H. Inaba and A. Kaneko (1998): Short-term variabilities of upper ocean current in the warm pool region during TOGA/COARE IOP. J. Oceanogr., 54, 227–240.
Webster, P. J. and R. Lukas (1992): TOGA COARE: The Coupled Ocean-Atmosphere Response Experiment. Bull. Amer. Meteor. Soc., 73, 1378–1416.
Wunsch, C. and A. E. Gill (1976): Observations of equatorially trapped waves in Pacific sea level variations. Deep-Sea Res., 23, 371–390.
Wyrtki, K. and B. Kilonsky (1984): Mean water and current structure during the Hawaii to Tahiti shuttle experiment. J. Phys. Oceanogr., 14, 242–254.
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Ueki, I., Kutsuwada, K., Inaba, H. et al. Quasi-2-Day Signals Observed in the Warm Pool Region during TOGA/COARE IOP. Journal of Oceanography 56, 539–552 (2000). https://doi.org/10.1023/A:1011101127617
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DOI: https://doi.org/10.1023/A:1011101127617