• Chelton, D. B., and R. E. Davis, 1982: Monthly mean sea level variability along the west coast of North America. J. Phys. Oceanogr.,12, 757–784.

  • ——, P. A. Bernal, and J. A. McGowan, 1982: Large-scale interannual physical and biological interaction in the California Current. J. Mar. Res.,40, 1095–1125.

  • Clarke, A. J., 1992: Low-frequency reflection from a nonmeridional eastern ocean boundary and the use of coastal sea level to monitor eastern Pacific equatorial Kelvin waves. J. Phys. Oceanogr.,22, 163–183.

  • ——, and X. Liu, 1994: Interannual sea level in the northern and eastern Indian Ocean. J. Phys. Oceanogr.,24, 1224–1235.

  • ——, and S. van Gorder, 1994: On ENSO coastal currents and sea levels. J. Phys. Oceanogr.,24, 661–680.

  • ——, and A. Lebedev, 1996: Long-term changes in the equatorial Pacific trade winds. J. Climate,9, 1020–1029.

  • Deser, C., and J. M. Wallace, 1990: Large-scale atmospheric circulation features of warm and cold episodes in the tropical Pacific. J. Climate,3, 1254–1281.

  • Diaz, H. F., and G. N. Kiladis, 1992: Atmospheric teleconnections associated with extreme phases of the Southern Oscillation. El Niño: Historical and Paleoclimatic Aspects of the Southern Oscillation, H. F. Diaz and V. Markgraf, Eds., Cambridge University Press, 7–28.

  • Enfield, D. B., and J. S. Allen, 1980: On the structure and dynamics of monthly mean sea level anomalies along the Pacific coast of North and South America. J. Phys. Oceanogr.,10, 557–578.

  • Godfrey, J. S., 1975: On ocean spindown. I. A linear experiment. J. Phys. Oceanogr.,5, 399–409.

  • Grimshaw, R., and J. S. Allen, 1988: Low-frequency baroclinic waves off coastal boundaries. J. Phys. Oceanogr.,18, 1124–1143.

  • Gutzler, D. S., 1992: Climate variability of temperature and humidity over the tropical western Pacific. Geophys. Res. Lett.,19, 1595–1598.

  • Kessler, W. S., 1990: Observations of long Rossby waves in the northern tropical Pacific. J. Geophys. Res.,95, 5183–5217.

  • Picaut, J., and T. Delcroix, 1995: Equatorial wave sequence associated with warm pool displacement during the 1986–1989 El Niño–La Niña. J. Geophys. Res.,100, 18 393–18 408.

  • Posmentier, E. S., M. A. Cane, and S. E. Zebiak, 1989: Tropical Pacific climate trends since 1960. J. Climate,2, 731–736.

  • Sturges, W., and B. G. Hong, 1995: Wind forcing of the Atlantic thermocline along 32°N at low frequencies. J. Phys. Oceanogr.,25, 1706–1715.

  • Wright, D. G., and K. R. Thompson, 1983: Time-averaged forms of the nonlinear stress law. J. Phys. Oceanogr.,13, 341–345.

  • Wyrtki, K., 1975: El Niño—The dynamic response of the equatorial Pacific Ocean to atmospheric forcing. J. Phys. Oceanogr.,5, 572–584.

  • Young, J. A., 1987: Boundary layer dynamics of tropical and monsoonal flows. Monsoon Meteorology, C.-P. Chang and T. N. Krishnamurti, Eds., Oxford University Press, 461–500.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 97 97 86
PDF Downloads 2 2 1

Interannual and Decadal Changes in Equatorial Wind Stress in the Atlantic, Indian, and Pacific Oceans and the Eastern Ocean Coastal Response

View More View Less
  • 1 Oceanography Department, The Florida State University, Tallahassee, Florida
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

Recently, Clarke and Lebedev showed that τ, the low-frequency eastward equatorial wind stress zonally averaged along the equator, can, in the case of the Pacific Ocean winds, be linearly estimated by Δp, the surface atmospheric pressure difference between the eastern and western ocean boundaries. The authors find that detrended interannual τ calculated from monthly winds is similarly linearly correlated with detrended Δp in the equatorial Atlantic and Indian Oceans since 1964 when enough wind data are available. The regression coefficient between τ and Δp enables the authors to estimate the turbulent stress atmospheric boundary layer height as being about 240 m for the equatorial Atlantic Ocean and 320 m for the equatorial Indian Ocean. Using a central Pacific pressure observation at 168°W, the authors similarly estimate the western and eastern Pacific turbulent stress atmospheric boundary layer heights as about 665 and 630 m, respectively.

Unlike the wind data, the pressure data do not contain systematic errors due to changing methods of measurement. Comparison of τ to Δp and τ from winds shows that there are strong false trends in Pacific and Atlantic τ estimated from winds. The τ from Δp records are not correlated on interannual timescales for any of the oceans, although the Indian and Pacific τ are negatively correlated if one restricts calculations to the period 1970–92. Decadal fluctuations are not visually correlated over the “short” records available. Most of the decadal Pacific variability comes from the western Pacific.

Theory and previous calculations for the Pacific indicate that interannual and decadal sea level on the eastern Pacific Ocean boundary is linearly related to τ. Calculations confirm this for the eastern Indian Ocean boundary and marginally support it for the Atlantic, where the low-frequency sea level records are short and of small amplitude. The Indian Ocean τ from Δp is much better correlated with sea level than τ from the winds. Large decadal sea level fluctuations occur on the eastern Indian Ocean boundary. On this timescale, anomalous westerly equatorial Indian Ocean winds have raised the Indian Ocean eastern boundary sea level since about 1970 and during most of the 1950s, while anomalous easterly equatorial Indian Ocean winds lowered the eastern Indian Ocean boundary sea level in the 1960s.

* Additional affiliation: Geophysical Fluid Dynamics Institute, Tallahassee, Florida.

Corresponding author address: Dr. Allan J. Clarke, Dept. of Oceanography, 3048, The Florida State University, Tallahassee, FL 32306-3048.

Email: clarke@ocean.fsu.edu

Abstract

Recently, Clarke and Lebedev showed that τ, the low-frequency eastward equatorial wind stress zonally averaged along the equator, can, in the case of the Pacific Ocean winds, be linearly estimated by Δp, the surface atmospheric pressure difference between the eastern and western ocean boundaries. The authors find that detrended interannual τ calculated from monthly winds is similarly linearly correlated with detrended Δp in the equatorial Atlantic and Indian Oceans since 1964 when enough wind data are available. The regression coefficient between τ and Δp enables the authors to estimate the turbulent stress atmospheric boundary layer height as being about 240 m for the equatorial Atlantic Ocean and 320 m for the equatorial Indian Ocean. Using a central Pacific pressure observation at 168°W, the authors similarly estimate the western and eastern Pacific turbulent stress atmospheric boundary layer heights as about 665 and 630 m, respectively.

Unlike the wind data, the pressure data do not contain systematic errors due to changing methods of measurement. Comparison of τ to Δp and τ from winds shows that there are strong false trends in Pacific and Atlantic τ estimated from winds. The τ from Δp records are not correlated on interannual timescales for any of the oceans, although the Indian and Pacific τ are negatively correlated if one restricts calculations to the period 1970–92. Decadal fluctuations are not visually correlated over the “short” records available. Most of the decadal Pacific variability comes from the western Pacific.

Theory and previous calculations for the Pacific indicate that interannual and decadal sea level on the eastern Pacific Ocean boundary is linearly related to τ. Calculations confirm this for the eastern Indian Ocean boundary and marginally support it for the Atlantic, where the low-frequency sea level records are short and of small amplitude. The Indian Ocean τ from Δp is much better correlated with sea level than τ from the winds. Large decadal sea level fluctuations occur on the eastern Indian Ocean boundary. On this timescale, anomalous westerly equatorial Indian Ocean winds have raised the Indian Ocean eastern boundary sea level since about 1970 and during most of the 1950s, while anomalous easterly equatorial Indian Ocean winds lowered the eastern Indian Ocean boundary sea level in the 1960s.

* Additional affiliation: Geophysical Fluid Dynamics Institute, Tallahassee, Florida.

Corresponding author address: Dr. Allan J. Clarke, Dept. of Oceanography, 3048, The Florida State University, Tallahassee, FL 32306-3048.

Email: clarke@ocean.fsu.edu

Save