On Equatorial Pacific Surface Wind Changes around 1977: NCEP–NCAR Reanalysis versus COADS Observations

Renguang Wu International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii

Search for other papers by Renguang Wu in
Current site
Google Scholar
PubMed
Close
and
Shang-Ping Xie International Pacific Research Center, and Department of Meteorology, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii

Search for other papers by Shang-Ping Xie in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

This note compares equatorial Pacific surface wind changes around 1977 in the NCEP–NCAR reanalysis and the Comprehensive Ocean–Atmosphere Data Set (COADS) observations. Significant discrepancies are found in wind changes over the equatorial central and eastern Pacific. In the NCEP–NCAR reanalysis, the easterlies weakened over the eastern equatorial Pacific, while the southerlies strengthened over the north equatorial central Pacific. As a result, the low-level convergence and precipitation decreased over the equatorial central Pacific. These wind and precipitation anomalies are opposite to those derived from the COADS observations. Independent observations of ocean heat content are used to validate the changes in equatorial zonal wind, and it is found that the zonal slope of the thermocline in an ocean model forced by the COADS wind is more consistent with ocean observations than forced by the reanalysis wind. The equatorial wind biases are also identified in the NCEP–NCAR reanalysis climatology, reaching a maximum in the cold season from August to October. This seasonality of wind biases calls for improved representation of atmospheric boundary layer processes in climate models.

Current affiliation: Center for Ocean–Land–Atmosphere Studies, Institute of Global Environment and Society, Inc., Calverton, Maryland

Corresponding author address: Renguang Wu, Center for Ocean–Land–Atmosphere Studies, Institute of Global Environment and Society, Inc., 4041 Powder Mill Road, Suite 302, Calverton, MD 20705. Email: renguang@cola.iges.org

Abstract

This note compares equatorial Pacific surface wind changes around 1977 in the NCEP–NCAR reanalysis and the Comprehensive Ocean–Atmosphere Data Set (COADS) observations. Significant discrepancies are found in wind changes over the equatorial central and eastern Pacific. In the NCEP–NCAR reanalysis, the easterlies weakened over the eastern equatorial Pacific, while the southerlies strengthened over the north equatorial central Pacific. As a result, the low-level convergence and precipitation decreased over the equatorial central Pacific. These wind and precipitation anomalies are opposite to those derived from the COADS observations. Independent observations of ocean heat content are used to validate the changes in equatorial zonal wind, and it is found that the zonal slope of the thermocline in an ocean model forced by the COADS wind is more consistent with ocean observations than forced by the reanalysis wind. The equatorial wind biases are also identified in the NCEP–NCAR reanalysis climatology, reaching a maximum in the cold season from August to October. This seasonality of wind biases calls for improved representation of atmospheric boundary layer processes in climate models.

Current affiliation: Center for Ocean–Land–Atmosphere Studies, Institute of Global Environment and Society, Inc., Calverton, Maryland

Corresponding author address: Renguang Wu, Center for Ocean–Land–Atmosphere Studies, Institute of Global Environment and Society, Inc., 4041 Powder Mill Road, Suite 302, Calverton, MD 20705. Email: renguang@cola.iges.org

Save
  • Cardone, V. J., J. G. Greenwood, and M. A. Cane, 1990: On trends in historical marine wind data. J. Climate, 3 , 113127.

  • Clarke, A. J., and A. Lebedev, 1996: Long-term changes in the equatorial Pacific trade winds. J. Climate, 9 , 10201029.

  • Clarke, A. J., and A. Lebedev, 1997: Interannual and interdecadal changes in equatorial wind stress in the Atlantic, Indian, and Pacific Oceans and the eastern ocean coastal response. J. Climate, 10 , 17221729.

    • Search Google Scholar
    • Export Citation
  • Gaffen, D. J., T. P. Barnett, and W. P. Elliott, 1991: Space and time scales of global tropospheric moisture. J. Climate, 4 , 9891008.

    • Search Google Scholar
    • Export Citation
  • Garreaud, R. D., and D. S. Battisti, 1999: Interannual (ENSO) and interdecadal (ENSO-like) variability in the Southern Hemisphere tropospheric circulation. J. Climate, 12 , 21132123.

    • Search Google Scholar
    • Export Citation
  • Goswami, B. N., and M. A. Thomas, 2000: Coupled ocean–atmosphere interdecadal modes in the tropics. J. Meteor. Soc. Japan, 78 , 765775.

    • Search Google Scholar
    • Export Citation
  • Graham, N. E., 1994: Decadal-scale climate variability in the tropical and North Pacific during the 1970s and 1980s: Observations and model results. Climate Dyn., 10 , 135162.

    • Search Google Scholar
    • Export Citation
  • Hashizume, H., S-P. Xie, M. Fujiwara, M. Shiotani, T. Watanabe, Y. Tanimoto, W. T. Liu, and K. Takeuchi, 2002: Direct observations of atmospheric boundary layer response to SST variations associated with tropical instability waves over the eastern equatorial Pacific. J. Climate, 15 , 33793393.

    • Search Google Scholar
    • Export Citation
  • Janowiak, J. E., A. Gruber, C. R. Kondragunta, R. E. Livezey, and G. J. Huffman, 1998: A comparison of the NCEP–NCAR reanalysis precipitation and the GPCP rain gauge–satellite combined dataset with observational error considerations. J. Climate, 11 , 29602979.

    • Search Google Scholar
    • Export Citation
  • Kachi, M., and T. Nitta, 1997: Decadal variations of the global atmosphere–ocean system. J. Meteor. Soc. Japan, 75 , 657675.

  • Kalnay, E,, and Coauthors. 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77 , 437471.

  • Kistler, R,, and Coauthors. 2001: The NCEP–NCAR 50-Year Reanalysis: Monthly means CD-ROM and documentation. Bull. Amer. Meteor. Soc., 82 , 247267.

    • Search Google Scholar
    • Export Citation
  • Krishnamurthy, V., and B. N. Goswami, 2000: Indian monsoon–ENSO relationship on interdecadal timescales. J. Climate, 13 , 579595.

  • Liu, W. T., X. Xie, P. S. Polito, S-P. Xie, and H. Hashizume, 2000: Atmospheric manifestation of tropical instability waves observed by QuickSCAT and Tropical Rainfall Measuring Mission. Geophys. Res. Lett., 27 , 25452548.

    • Search Google Scholar
    • Export Citation
  • Morrissey, M. L., and N. E. Graham, 1996: Recent trends in rain gauge precipitation measurements from the tropical Pacific: Evidence for an enhanced hydrologic cycle. Bull. Amer. Meteor. Soc., 77 , 12071219.

    • Search Google Scholar
    • Export Citation
  • Nitta, T., and M. Kachi, 1994: Interdecadal variations of precipitation over the tropical Pacific and Indian Oceans. J. Meteor. Soc. Japan, 72 , 823831.

    • Search Google Scholar
    • Export Citation
  • Nitta, T., and S. Yamada, 1989: Recent warming of tropical sea surface temperature and its relationship to the Northern Hemisphere circulation. J. Meteor. Soc. Japan, 67 , 375383.

    • Search Google Scholar
    • Export Citation
  • Philander, S. G. H., 1990: El Niño, La Niña, and the Southern Oscillation. Academic Press, 293 pp.

  • Posmentier, E. S., M. A. Cane, and S. E. Zebiak, 1989: Tropical Pacific climate trends since 1960. J. Climate, 2 , 731736.

  • Putman, W. M., D. M. Legler, and J. J. O’Brien, 2000: Interannual variability of synthesized FSU and NCEP–NCAR reanalysis pseudostress products over the Pacific Ocean. J. Climate, 13 , 30033016.

    • Search Google Scholar
    • Export Citation
  • Sadler, J. C., M. A. Lander, A. M. Hori, and L. K. Oda, 1987: Tropical marine climate atlas. Vol. 1. Pacific Ocean. Rep. UHMET 87-02, Dept. of Meteorology, University of Hawaii at Manoa, 27 pp. [Available from Department of Meteorology, University of Hawaii at Manoa, 2525 Correa Rd., Honolulu, HI 96822.].

    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., 1990: Recent observed interdecadal climate changes in the Northern Hemisphere. Bull. Amer. Meteor. Soc., 71 , 988993.

    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., and J. W. Hurrell, 1994: Decadal atmosphere–ocean variations in the Pacific. Climate Dyn., 9 , 303319.

  • Trenberth, K. E., J. W. Stepaniak, and M. Fiorino, 2001: Quality of reanalysis in the Tropics. J. Climate, 14 , 14991510.

  • Wallace, J. M., T. P. Mitchell, and C. Deser, 1989: The influence of sea-surface temperature on surface wind in the eastern equatorial Pacific: Seasonal and interannual variability. J. Climate, 2 , 14921499.

    • Search Google Scholar
    • Export Citation
  • Wang, B., 1995: Interdecadal change in El Niño onset in the last four decades. J. Climate, 8 , 267285.

  • Wang, B., T. Li, and P. Chang, 1995: An intermediate ocean model of the tropical Pacific Ocean. J. Phys. Oceanogr., 25 , 15991616.

  • Ward, M. N., 1992: Provisionally corrected surface wind data, worldwide ocean–atmosphere surface fields, and Sahelian rainfall variability. J. Climate, 5 , 454475.

    • Search Google Scholar
    • Export Citation
  • Ward, M. N., and B. J. Hoskins, 1996: Near-surface wind over the global ocean 1949–1988. J. Climate, 9 , 18771895.

  • White, W. B., 1995: Design of a global observing system for gyre-scale upper ocean temperature variability. Progress in Oceanography, Vol. 36, Pergamon, 169–217.

    • Search Google Scholar
    • Export Citation
  • Woodruff, S. D., R. J. Slutz, R. L. Jenne, and P. M. Steurer, 1987: A comprehensive ocean–atmosphere data set. Bull. Amer. Meteor. Soc., 68 , 12391350.

    • Search Google Scholar
    • Export Citation
  • World Climate Research Programme, 1998: Proc. First WCRP Int. Conf. on Reanalysis. WCRP-104, WMO/TD-876, Silver Spring, MD, World Meteorological Organization, 461 pp.

    • Search Google Scholar
    • Export Citation
  • World Climate Research Programme, 2000: Proc. Second WCRP Int. Conf. on Reanalysis. WCRP-109, WMO/TD-985, Silver Spring, MD, World Meteorological Organization, 452 pp.

    • Search Google Scholar
    • Export Citation
  • World Climate Research Programme, 2001: Report of the Joint WCRP/SCOR Working Group on Air–Sea Fluxes—Intercomparison and Validation of Ocean–Atmosphere Energy Flux Fields. WCRP-112, WMO/TD-1036, World Meteorological Organization, 307 pp.

    • Search Google Scholar
    • Export Citation
  • Xie, P., and P. A. Arkin, 1997: Global precipitation: A 17-yr monthly analysis based on gauge observations, satellite estimates, and numerical model outputs. Bull. Amer. Meteor. Soc., 78 , 25392558.

    • Search Google Scholar
    • Export Citation
  • Xie, S-P., T. Kunitani, A. Kubokawa, M. Nonaka, and S. Hosoda, 2000: Interdecadal thermocline variability in the North Pacific for 1958–97: A GCM simulation. J. Phys. Oceanogr., 30 , 27982813.

    • Search Google Scholar
    • Export Citation
  • Zhang, Y., J. M. Wallace, and D. S. Battisti, 1997: ENSO-like decade-to-century scale variability: 1900–93. J. Climate, 10 , 10041020.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 217 31 6
PDF Downloads 65 19 3