Tropical Coupled Rossby Waves in the Pacific Ocean–Atmosphere System

Warren B. White Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California

Search for other papers by Warren B. White in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

Gridded fields of TOPEX/Poseidon sea level height (SLH) and National Centers for Environmental Prediction sea surface temperature (SST) and meridional surface wind (MSW) anomalies are constructed monthly on a 2° grid over the Pacific Ocean for nearly 6 years from 1993 to 1998. Time–longitude diagrams of monthly SLH, SST, and MSW anomalies from 10° to 22° lat yield significant peak spectral energy density in zonal wavenumber-frequency spectra for periods of 1–2 yr near the free Rossby wave dispersion curve. Subsequently, temporal and spatial filtering of these SLH, SST, and MSW anomalies finds them propagating westward over the interior tropical Pacific Ocean in fixed phase with one another. Significant squared coherence exists between filtered SLH and SST (SST and MSW) anomalies over the entire latitude band, yielding significant phase differences ranging over 90° ± 45° (−70° ± 45°) at 10°S and 14° lat and ranging over 90° ± 45° (0° ± 45°) at 18° and 22° lat. Over the entire latitude domain warm SST anomalies are displaced westward of high SLH anomalies, consistent with anomalous poleward geostrophic heat advection associated with baroclinic Rossby waves. At 18° and 22° lat poleward MSW anomalies occur directly over warm SST anomalies as observed previously for extratropical coupled Rossby waves. On the other hand, at 10°S and 14° lat poleward MSW anomalies are displaced eastward of warm SST anomalies, consistent with Newtonian cooling balancing SST-induced midlevel diabatic heating in the tropical troposphere. The latter relationship allows an analytical model of tropical coupled Rossby waves to be constructed at 10° and 14° lat, different from that of extratropical Rossby waves at 18° and 22° lat and from that of free Rossby waves expected over the entire latitude domain. This tropical model yields coupled Rossby waves that propagate westward at slower phase speeds than expected of free Rossby waves, as observed. Maintenance (growth) of wave amplitude against dissipation occurs for tropical coupled Rossby waves that travel parallel to (poleward of) isotherms in the mean SST distribution, as observed.

Corresponding author address: Dr. Warren B. White, Physical Oceanography Division, Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093-0230.

Email: wbwhite@ucsd.edu

Abstract

Gridded fields of TOPEX/Poseidon sea level height (SLH) and National Centers for Environmental Prediction sea surface temperature (SST) and meridional surface wind (MSW) anomalies are constructed monthly on a 2° grid over the Pacific Ocean for nearly 6 years from 1993 to 1998. Time–longitude diagrams of monthly SLH, SST, and MSW anomalies from 10° to 22° lat yield significant peak spectral energy density in zonal wavenumber-frequency spectra for periods of 1–2 yr near the free Rossby wave dispersion curve. Subsequently, temporal and spatial filtering of these SLH, SST, and MSW anomalies finds them propagating westward over the interior tropical Pacific Ocean in fixed phase with one another. Significant squared coherence exists between filtered SLH and SST (SST and MSW) anomalies over the entire latitude band, yielding significant phase differences ranging over 90° ± 45° (−70° ± 45°) at 10°S and 14° lat and ranging over 90° ± 45° (0° ± 45°) at 18° and 22° lat. Over the entire latitude domain warm SST anomalies are displaced westward of high SLH anomalies, consistent with anomalous poleward geostrophic heat advection associated with baroclinic Rossby waves. At 18° and 22° lat poleward MSW anomalies occur directly over warm SST anomalies as observed previously for extratropical coupled Rossby waves. On the other hand, at 10°S and 14° lat poleward MSW anomalies are displaced eastward of warm SST anomalies, consistent with Newtonian cooling balancing SST-induced midlevel diabatic heating in the tropical troposphere. The latter relationship allows an analytical model of tropical coupled Rossby waves to be constructed at 10° and 14° lat, different from that of extratropical Rossby waves at 18° and 22° lat and from that of free Rossby waves expected over the entire latitude domain. This tropical model yields coupled Rossby waves that propagate westward at slower phase speeds than expected of free Rossby waves, as observed. Maintenance (growth) of wave amplitude against dissipation occurs for tropical coupled Rossby waves that travel parallel to (poleward of) isotherms in the mean SST distribution, as observed.

Corresponding author address: Dr. Warren B. White, Physical Oceanography Division, Scripps Institution of Oceanography, 9500 Gilman Dr., La Jolla, CA 92093-0230.

Email: wbwhite@ucsd.edu

Save
  • Bendat, J. S., and A. G. Piersol, 1986: Random Data: Analysis and Measurement Procedures. John Wiley & Sons, 566 pp.

  • Chatfield, C., 1989: The Analysis of Time Series: An Introduction. Chapman and Hall, 241 pp.

  • Frankignoul, C., and R. W. Reynolds, 1983: Testing a dynamic model for mid-latitude sea surface temperature. J. Phys. Oceanogr.,13, 1131–1145.

  • Gill, A. E., 1980: Some simple solutions for heat induced tropical circulation. Quart. J. Roy. Meteor. Soc.,106, 447–462.

  • ——, 1982: Atmosphere–Ocean Dynamics. Academic Press, 662 pp.

  • Jackson, L. B., 1996: Digital Filters and Signal Processing. Kluwer Academic, 502 pp.

  • Jacobs, G. A., and J. L. Mitchell, 1996: Ocean circulation variations associated with the Antarctic Circumpolar Wave. Geophys. Res. Lett.,23, 2947–2950.

  • Jenkins, G. M., and D. G. Watts, 1968: Spectral Analysis and Its Applications. Holden-Day, 502 pp.

  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc.,77, 437–471.

  • Kessler, W. S., 1990: Observation of long Rossby waves in the northern tropical Pacific. J. Geophys. Res.,95, 5813–5219.

  • Killworth, P. D., D. B. Chelton, and R. A. deZoeke, 1997: The speed of observed and theoretical long extratropical planetary waves. J. Phys. Oceanogr.,27, 1946–1966.

  • Large, W. G., and S. Pond, 1981: Open ocean momentum flux measurements in moderate to strong winds. J. Phys. Oceanogr.,11, 324.

  • Palmer, T. N., and Z. Sun, 1985: A modeling and observational study of the relationship between sea surface temperature in the north-west Atlantic and the atmospheric general circulation. Quart. J. Roy. Meteor. Soc.,111, 947–975.

  • Reynolds, R. W., and D. C. Marsico, 1993: An improved real-time global sea surface temperature analysis. J. Climate,6, 114–119.

  • Sverdrup, H. U., M. W. Johnson, and R. H. Fleming, 1942: The Oceans, Their Physics, Chemistry, and General Biology. Prentice-Hall, 1060 pp.

  • Wang, C., and R. H. Weisberg, 1994: Equatorial trapped waves of a coupled ocean–atmosphere system. J. Phys. Oceanogr.,24, 1978–1998.

  • ——, and ——, 1996: Stability of equatorial modes in a simplified coupled ocean–atmosphere model. J. Climate,9, 3132–3148.

  • Ward, M. N., and B. J. Hoskins, 1996: Near surface winds over the global ocean 1949–1988. J. Climate,9, 1877–1895.

  • White, W. B., 1977: Annual forcing of baroclinic long waves in the tropical North Pacific. J. Phys. Oceanogr.,7, 50–61.

  • ——, and J. F. T. Saur, 1983: Sources of interannual baroclinic waves in the eastern subtropical North Pacific. J. Phys. Oceanogr.,13, 1035–1046.

  • ——, and R. Peterson, 1996: An Antarctic circumpolar wave in surface pressure, wind, temperature, and sea ice extent. Nature,380, 699–702.

  • ——, and D. R. Cayan, 2000: A global ENSO wave in surface temperature and pressure, and its interdecadal modulation from 1900 to 1996. J. Geophys. Res., in press.

  • ——, Y. Chao, and C.-K. Tai, 1998a: Coupling of biennial oceanic Rossby waves with the overlying atmosphere in the Pacific basin. J. Phys. Oceanogr.,28, 1236–1251.

  • ——, S.-C. Chen, and R. Peterson, 1998b: The Antarctic Circumpolar Wave: A beta-effect in ocean–atmosphere coupling over the Southern Ocean. J. Phys. Oceanogr.,28, 2345–2361.

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

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 321 30 0
PDF Downloads 108 17 0