• Aiyyer, A. R., , and J. Molinari, 2003: Evolution of mixed Rossby–gravity waves in idealized MJO environments. J. Atmos. Sci., 60 , 28372855.

    • Search Google Scholar
    • Export Citation
  • Chang, C-P., , J-M. Chen, , P. A. Harr, , and L. E. Carr, 1996: Northwestward-propagating wave patterns over the tropical western North Pacific during summer. Mon. Wea. Rev., 124 , 22452266.

    • Search Google Scholar
    • Export Citation
  • Dickinson, M., , and J. Molinari, 2002: Mixed Rossby–gravity waves and western tropical Pacific cyclogenesis. Part I: Synoptic evolution. J. Atmos. Sci., 59 , 21832196.

    • Search Google Scholar
    • Export Citation
  • Held, I. M., , and M. J. Suarez, 1994: A proposal for the intercomparison of the dynamical cores of atmospheric general-circulation models. Bull. Amer. Meteor. Soc., 75 , 18251830.

    • Search Google Scholar
    • Export Citation
  • Holland, G. J., 1995: Scale interaction in the western Pacific monsoon. Meteor. Atmos. Phys., 56 , 5779.

  • Jiang, X., , and T. Li, 2005: Reinitiation of the boreal summer intraseasonal oscillation in the tropical Indian Ocean. J. Climate, 18 , 3773795.

    • Search Google Scholar
    • Export Citation
  • Jiang, X., , T. Li, , and B. Wang, 2004: Structures and mechanisms of the northward propagating boreal summer intraseasonal oscillation. J. Climate, 17 , 10221039.

    • Search Google Scholar
    • Export Citation
  • Kuo, H-C., , J-H. Chen, , R. T. Williams, , and C-P. Chang, 2001: Rossby wave in zonally opposing mean flow: Behavior in northwest Pacific summer monsoon. J. Atmos. Sci., 58 , 10351050.

    • Search Google Scholar
    • Export Citation
  • Kuo, H-L., 1974: Further studies of the parameterization of the influence of cumulus convection on large-scale flow. J. Atmos. Sci., 31 , 12311240.

    • Search Google Scholar
    • Export Citation
  • Lau, K-H., , and N-C. Lau, 1990: Observed structure and propagation characteristics of tropical summertime synoptic scale disturbances. Mon. Wea. Rev., 118 , 18881913.

    • Search Google Scholar
    • Export Citation
  • Lau, K-H., , and N-C. Lau, 1992: The energetics and propagation dynamics of tropical summertime synoptic-scale disturbances. Mon. Wea. Rev., 120 , 25232539.

    • Search Google Scholar
    • Export Citation
  • Li, T., , and B. Wang, 1994: The influence of sea surface temperature on the tropical intraseasonal oscillation: A numerical study. Mon. Wea. Rev., 122 , 23492362.

    • Search Google Scholar
    • Export Citation
  • Li, T., , and B. Fu, 2006: Tropical cyclogenesis associated with Rossby wave energy dispersion of a preexisting typhoon. Part I: Satellite data analyses. J. Atmos. Sci., in press.

    • Search Google Scholar
    • Export Citation
  • Li, T., , B. Fu, , X. Ge, , B. Wang, , and M. Peng, 2003: Satellite data analysis and numerical simulation of tropical cyclone formation. Geophy. Res. Lett., 30 .2122, doi:10.1029/2003GL018556.

    • Search Google Scholar
    • Export Citation
  • Li, T., , X. Ge, , B. Wang, , and Y. Zhu, 2006: Tropical cyclogenesis associated with Rossby wave energy dispersion of a pre-existing typhoon. Part II: Numerical simulations. J. Atmos. Sci., in press.

    • Search Google Scholar
    • Export Citation
  • Liebmann, B., , and H. H. Hendon, 1990: Synoptic-scale disturbances near the equator. J. Atmos. Sci., 47 , 14631479.

  • Matsuno, T., 1966: Quasi-geostrophic motions in the equatorial area. J. Meteor. Soc. Japan, 44 , 2543.

  • Nitta, T., , and M. Yanai, 1969: A note on the barotropic instability of the tropical easterly current. J. Meteor. Soc. Japan, 47 , 127130.

    • Search Google Scholar
    • Export Citation
  • Tai, K. S., , and Y. Ogura, 1987: An observational study of easterly waves over the eastern Pacific in the northern summer using FGGE data. J. Atmos. Sci., 44 , 339361.

    • Search Google Scholar
    • Export Citation
  • Takayabu, Y. N., , and T. Nitta, 1993: 3–5 day disturbances coupled with convection in the tropical Pacific Ocean. J. Meteor. Soc. Japan, 71 , 221245.

    • Search Google Scholar
    • Export Citation
  • Tam, C-Y., , and T. Li, 2006: The origin and dispersion characteristics of the observed tropical summertime synoptic-scale waves over the western Pacific. Mon. Wea. Rev., in press.

    • Search Google Scholar
    • Export Citation
  • Ting, M., , and L. Yu, 1998: Steady response to tropical heating in wavy linear and nonlinear baroclinic models. J. Atmos. Sci., 55 , 35653582.

    • Search Google Scholar
    • Export Citation
  • Wang, B., , and T. Li, 1993: A simple tropical atmospheric model of relevance to short-term climate variations. J. Atmos. Sci., 50 , 260284.

    • Search Google Scholar
    • Export Citation
  • Wang, B., , and T. Li, 1994: Convective interaction with boundary-layer dynamics in the development of a tropical intraseasonal system. J. Atmos. Sci., 51 , 13861400.

    • Search Google Scholar
    • Export Citation
  • Wang, B., , and X. Xie, 1996: Low-frequency equatorial waves in sheared zonal flow. Part I: Stable waves. J. Atmos. Sci., 53 , 449467.

  • Wang, B., , R. Wu, , and T. Li, 2003: Atmosphere–warm ocean interaction and its impact on Asian–Australian monsoon variation. J. Climate, 16 , 11951211.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 68 68 13
PDF Downloads 46 46 11

Origin of the Summertime Synoptic-Scale Wave Train in the Western North Pacific

View More View Less
  • 1 International Pacific Research Center and Department of Meteorology, University of Hawaii at Manoa, Honolulu, Hawaii
© Get Permissions
Restricted access

Abstract

The origin of the summertime synoptic wave train in the western North Pacific is investigated with a multilevel, nonlinear baroclinic model. A realistic three-dimensional summer mean state is specified and eigenvectors are calculated by introducing small perturbation initially to the model. Numerical experiments indicate that the origin of the synoptic wave train may arise from instability of the summer mean flow in the presence of a convection–frictional convergence (CFC) feedback. In the lack of the CFC feedback, the summer mean flow supports only a least damped mode, characterized by a northwest–southeast-oriented wave train pattern with a zonal wavelength of 2500 km. In the presence of both the realistic summer mean flow and the CFC feedback, the model reproduces a fast growing mode, whose structure and propagation characters are similar to the observed.

Sensitivity experiments with different initial perturbation patterns indicate that the model solution is not sensitive to initial conditions. Further sensitivity experiments reveal that the basic-state vertical shear may affect the growth rate and propagation character of the wave train. An easterly shear may lead to a faster growth and northwestward phase propagation, whereas a westerly shear may favor a slower growth and southeastward phase propagation.

* School of Ocean and Earth Science and Technology Contribution Number 6715 and International Pacific Research Center Contribution Number 351

Corresponding author address: Prof. Tim Li, IPRC, University of Hawaii at Manoa, 2525 Correa Rd., Honolulu, HI 96822. Email: timli@hawaii.edu

Abstract

The origin of the summertime synoptic wave train in the western North Pacific is investigated with a multilevel, nonlinear baroclinic model. A realistic three-dimensional summer mean state is specified and eigenvectors are calculated by introducing small perturbation initially to the model. Numerical experiments indicate that the origin of the synoptic wave train may arise from instability of the summer mean flow in the presence of a convection–frictional convergence (CFC) feedback. In the lack of the CFC feedback, the summer mean flow supports only a least damped mode, characterized by a northwest–southeast-oriented wave train pattern with a zonal wavelength of 2500 km. In the presence of both the realistic summer mean flow and the CFC feedback, the model reproduces a fast growing mode, whose structure and propagation characters are similar to the observed.

Sensitivity experiments with different initial perturbation patterns indicate that the model solution is not sensitive to initial conditions. Further sensitivity experiments reveal that the basic-state vertical shear may affect the growth rate and propagation character of the wave train. An easterly shear may lead to a faster growth and northwestward phase propagation, whereas a westerly shear may favor a slower growth and southeastward phase propagation.

* School of Ocean and Earth Science and Technology Contribution Number 6715 and International Pacific Research Center Contribution Number 351

Corresponding author address: Prof. Tim Li, IPRC, University of Hawaii at Manoa, 2525 Correa Rd., Honolulu, HI 96822. Email: timli@hawaii.edu

Save