Westerly Wind Events in the Tropical Pacific, 1986–95

D. E. Harrison NOAA/PMEL and JISAO/Hayes Center, University of Washington, Seattle, Washington

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Gabriel A. Vecchi School of Oceanography, University of Washington, Seattle, Washington

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Abstract

Based on examination of 10 yr of 10-m winds and wind anomalies from European Centre for Medium-Range Weather Forecasts (ECWMF) analysis, definitions for westerly wind events (WWEs) of eight different types are proposed. The authors construct a composite for each type of event, show that a simple propagating Gaussian model satisfactorily describes the evolution of zonal wind anomaly for each type of event, and determine the scales of each composite event by fitting the model to each composite. The authors discuss the WWEs that occurred during the Tropical Oceans Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE) intensive observing period (IOP) and show the extent to which these composite events are able to reproduce the major westerly wind features of the IOP. The frequency of occurrence of each type of WWE for each year of this record and by calendar month are described; the authors find several types of events are negatively correlated with the annual mean troup Southern Oscillation index (SOI), and that the stronger WWEs often have a statistically significant seasonality. Several instances of widespread westerly wind anomaly are identified and described, but these “mega”-WWEs have few features in common. Although the authors’ composites underestimate the peak amplitude of many WWEs and cannot always accurately represent the time evolution of each WWE, the authors believe that they offer a useful framework for representing the sort of westerly wind variability that occurs in the western and central tropical Pacific and can provide a basis for further study of the importance of such winds in the climatological and interannual variability of this part of the World Ocean.

Corresponding author address: Dr. D. E. Harrison, NOAA/PMEL/OCRD, 7600 Sand Point Way, NE, Seattle, WA 98115.

Email: harrison@pmel.noaa.gov

Abstract

Based on examination of 10 yr of 10-m winds and wind anomalies from European Centre for Medium-Range Weather Forecasts (ECWMF) analysis, definitions for westerly wind events (WWEs) of eight different types are proposed. The authors construct a composite for each type of event, show that a simple propagating Gaussian model satisfactorily describes the evolution of zonal wind anomaly for each type of event, and determine the scales of each composite event by fitting the model to each composite. The authors discuss the WWEs that occurred during the Tropical Oceans Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE) intensive observing period (IOP) and show the extent to which these composite events are able to reproduce the major westerly wind features of the IOP. The frequency of occurrence of each type of WWE for each year of this record and by calendar month are described; the authors find several types of events are negatively correlated with the annual mean troup Southern Oscillation index (SOI), and that the stronger WWEs often have a statistically significant seasonality. Several instances of widespread westerly wind anomaly are identified and described, but these “mega”-WWEs have few features in common. Although the authors’ composites underestimate the peak amplitude of many WWEs and cannot always accurately represent the time evolution of each WWE, the authors believe that they offer a useful framework for representing the sort of westerly wind variability that occurs in the western and central tropical Pacific and can provide a basis for further study of the importance of such winds in the climatological and interannual variability of this part of the World Ocean.

Corresponding author address: Dr. D. E. Harrison, NOAA/PMEL/OCRD, 7600 Sand Point Way, NE, Seattle, WA 98115.

Email: harrison@pmel.noaa.gov

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  • Bickel, P. J., and K. A. Doksum, 1977: Mathematical Statistics: Basic Ideas and Selected Topics. Holden-Day, 492 pp.

  • Chen, S. S., R. A. Houze Jr., and B. E. Mapes, 1996: Multiscale variability of deep convection in relation to large-scale circulation in TOGA COARE. J. Atmos. Sci.,53, 1380–1409.

  • Chu, P. S., 1988: Extratropical forcing and the burst of equatorial westerlies in the western Pacific: A synoptic study. J. Meteor. Soc. Japan,66, 4549–4564.

  • ——, and J. Frederick, 1990: Westerly wind bursts and surface heat fluxes in the equatorial western Pacific in May 1982. J. Meteor. Soc. Japan,68, 5523–5536.

  • Delcroix, T., G. Eldin, M. McPhaden, and A. Morliere, 1993: Effects of westerly wind bursts upon the western equatorial Pacific Ocean, February–April 1991. J. Geophys. Res.,98, 16379–16385.

  • ECMWF, 1989: The description of the ECMWF/WCRP level III—A global atmospheric data archive. Tech. Attachment, 72 pp. [Available from ECMWF, Shinfield Park, Reading RG2 9AX, United Kingdom.].

  • Efron, B., and R. Tibshirani, 1991: Statistical data analysis in the computer age. Science,253, 390–395.

  • Eldin, G., T. Delcroix, C. Hénin, K. Richards, Y. Du Penhoat, J. Picaut, and P. Rual, 1994: Large-scale current and thermohaline structures along 156°E during the COARE intensive observation period. Geophys. Res. Lett.,21, 2681–2684.

  • Geise, B. S., and D. E. Harrison, 1990: Aspects of the Kelvin wave response to episodic wind forcing. J. Geophys. Res.,95(C5), 7289–7312.

  • ——, and ——, 1991: Eastern equatorial Pacific response to three composite westerly wind types. J. Geophys. Res.,96(Suppl.), 3239–3248.

  • Gill, A. E., 1982: Atmosphere-Ocean Dynamics. Academic Press, 662 pp.

  • Harrison, D. E., 1984: On the appearance of sustained equatorial westerlies during the 1982 Pacific warm event. Science,225, 1099–1102.

  • ——, and P. S. Schopf, 1984: Kelvin-wave-induced anomalous advection and the onset of surface warming in El Niño events. Mon. Wea. Rev.,112, 923–933.

  • ——, and B. S. Geise, 1988: Remote westerly wind forcing of the eastern equatorial Pacific: Some model results. Geophys. Res. Lett.,15, 804–807.

  • ——, and D. S. Luther, 1990: Surface winds from tropical Pacific islands—Climatological statistics. J. Climate,3, 2251–2271.

  • ——, and B. S. Geise, 1991: Episodes of surface westerly winds as observed from islands in the western tropical Pacific. J. Geophys. Res.,96, 3221–3237.

  • ——, and N. Larkin, 1996: The COADS sea level pressure signal: A near-global El Niño composite and time series view, 1946–93. J. Climate,9, 3025–3055.

  • ——, and ——, 1997: The ENSO surface temperature and wind signal: A near-global composite and time-series view, 1946–1995. Rev. Geophys., in press..

  • Hartten, L. M., 1996: Synoptic settings of westerly wind bursts. J. Geophys. Res.,101(D12), 16997–17019.

  • Joint Typhoon Warning Center, 1994a: Western North Pacific typhoons—1994. Mar. Wea. Log,38(1), 34–40.

  • ——, 1994b: Western North Pacific typhoons—1993. Mar. Wea. Log,38(4), 16–23.

  • Keen, R. A., 1982: The role of cross-equatorial cyclone pairs in the Southern Oscillation. Mon. Wea. Rev.,110, 1405–1416.

  • Kiladis, G. N., G. A. Meehl, and K. M. Weickmann, 1994: Large- scale circulation associated with westerly wind bursts and deep convection over the western equatorial Pacific. J. Geophys. Res.,99(D9), 18527–18544.

  • Kindle, J. C., and P. A. Phoebus, 1995: The ocean response to operational wind bursts during the 1991–1992 El Niño. J. Geophys. Res.,100(C3), 4803–4920.

  • Large, W. G., and S. Pond, 1981: Open ocean momentum flux measurments in moderate to strong winds. J. Phys. Oceanogr.,11, 324–336.

  • Lau, K. H., and N. C. Lau, 1992: The energetics and propagation dynamics of tropical summertime synoptic-scale disturbances. Mon. Wea. Rev.,120, 2523–2539.

  • Lau, K. M., L. Peng, C. H. Sui, and T. Nakazawa, 1989: Dynamics of super cloud clusters, westerly wind bursts, 30–60-day oscillations and ENSO: A unified view. J. Meteor. Soc. Japan,67, 2205–2219.

  • Lin, X., and R. H. Johnson, 1996: Kinematic and thermodynamic characteristics of the flow over the western Pacific warm pool during TOGA COARE. J. Atmos. Sci.,53, 5695–5715.

  • Livezey, R. E., and W. Y. Chen, 1983: Statistical field significance and its determination by Monte Carlo techniques. Mon. Wea. Rev.,111, 47–59.

  • Love, G., 1985: Cross-equatorial influence of winter hemisphere subtropical cold surges. Mon. Wea. Rev.,113, 1487–1498.

  • Lukas, R., P. J. Webster, M. Ji, and A. Leetma, 1995: The large-scale context for the TOGA Coupled Ocean-Atmosphere Response Experiment. Meteor. Atmos. Phys.,56, 3–16.

  • Luther, D. S., D. E. Harrison, and R. A. Knox, 1983: Zonal winds in the central equatorial Pacific and El Niño. Science,222, 327–330.

  • Madden, R. A., and P. R. Julian, 1972: Description of global-scale circulation cells in the tropics with a 40–50-day period. J. Atmos. Sci.,29, 1109–1123.

  • ——, and ——, 1994: Observations of the 40–50-day tropical oscillation—A review. Mon. Wea. Rev.,122, 814–837.

  • Mangum, L. J., H. P. Freitag, and M. J. McPhaden, 1994: TOGA- TAO array sampling schemes and sensor evaluations. Proc. Oceans ’94 OSATES,II, 402–406.

  • McBride, J. L., N. E. Davidson, K. Puri, and G. C. Tyrell, 1995: The flow during TOGA COARE as diagnosed by the BMRC tropical analysis and prediction system. Mon. Wea. Rev.,123, 717–736.

  • McPhaden, M. J., 1993: TOGA-TAO and the 1991–93, El Niño–Southern Oscillation Event. Oceanography,6(2), 36–44.

  • ——, F. Bahr, Y. Du Penhoat, E. Firing, S. P. Hayes, P. P. Niiler, P. L. Richardson, and J. M. Toole, 1992: The response of the western equatorial Pacific Ocean to westerly wind bursts during November 1989 to January 1990. J. Geophys. Res.,97, 14289–14303.

  • Meehl, G. A., G. N. Kiladis, K. M. Weickmann, M. Wheeler, D. S. Gutzler, and G. P. Compo, 1996: Modulation of equatorial subseasonal convective episodes by tropical-extratropical interaction in the Indian and Pacific Ocean regions. J. Geophys. Res.,101(D10), 15033–15049.

  • Rasmusson, E. M., and T. H. Carpenter, 1982: Variations in tropical sea surface temperature and surface wind fields associated with the Southern Oscillation/El Niño. Mon. Wea. Rev.,110, 354–384.

  • Rui, H., and B. Wang, 1990: Development characteristics and dynamic structure of tropical intraseasonal convection anomalies. J. Atmos. Sci.,47, 357–379.

  • Shopf, P. S., and D. E. Harrison, 1983: On equatorial Kelvin waves and El Niño, I, Influence of initial states on wave-induced current and warming. J. Phys. Oceanogr.,13, 936–948.

  • Spiegel, M. R., 1994: Theory and Problems of Statistics. Schaum’s Outline Series, McGraw-Hill, 504 pp.

  • Sui, C. H., and K. M. Lau, 1992: Multiscale phenomena in the tropical atmosphere over the western Pacific. Mon. Wea. Rev.,120, 407–430.

  • Tsutsui, J., and A. Kasahara, 1996: Simulated tropical cyclones using the National Center for Atmospheric Research community climate model. J. Geophys. Res.,101(D10), 15013–15032.

  • Vecchi, G. A., and D. E. Harrison, 1997: Westerly wind events in the tropical Pacific, 1986–1995; An atlas. NOAA/PMEL Tech. Memo. ERL PMEL-109, 222 pp. [Available from NTIS, 5285 Port Royal Rd., Springfield, VA 22161.].

  • Webster, P. J., and R. Lukas, 1992: TOGA COARE: The Coupled Ocean–Atmosphere Response Experiment. Bull. Amer. Meteor. Soc.,73, 1377–1416.

  • 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, 1239–1250.

  • Zwillinger, D., Ed., 1996: CRC—Standard Mathematical Tables and Formulae. 30th ed. CRC Press, 812 pp.

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