Climate Dynamics

, Volume 42, Issue 5–6, pp 1217–1227 | Cite as

ENSO-phase dependent TD and MRG wave activity in the western North Pacific

  • Liang Wu
  • Zhiping WenEmail author
  • Tim Li
  • Ronghui Huang


The three-dimensional structure and evolution characteristics of tropical depression (TD) and mixed Rossby-gravity wave (MRG) type disturbances in the tropical western North Pacific during El Niño and La Niña summers are investigated based on observational and reanalysis data. A clear MRG-to-TD transition was observed during El Niño summers while such a transition is unclear during La Niña summers. The vertical structure of the TD-MRG waves appears equivalent barotropic during El Niño but becomes tilted eastward with height during La Niña. The diagnosis of barotropic energy conversion shows that both the rotational and divergent components of the background flow change associated with E1 Niño-Southern Oscillation (ENSO) are responsible for energy conversion from the mean flow to the TD-MRG perturbations. A further examination of the pure MRG mode shows that its intensity does not vary between El Niño and La Niña while its phase speed does. A faster (slower) westward propagation speed during La Niña (El Niña) is attributed to enhanced (reduced) mean easterlies in the western equatorial Pacific. The heating associated with the MRG wave appears more anti-symmetric during La Niña than during El Niño. In contrast to the MRG waves, the amplitude of the TD waves depends greatly on the ENSO phase. The enhanced (suppressed) TD disturbances during El Niño (La Niña) is attributed to greater (less) barotropic energy conversion associated with the background flow change. The vertical structure of the TD waves appears quasi-barotropic in the geopotential height field but baroclinic in the divergence field.


ENSO MRG waves TD waves Western North Pacific 



This work is jointly supported by the National Natural Science Foundation of China Grant 41205052, 41230527, and 41175076, the Knowledge Innovation Program of the Chinese Academy of Sciences Grant KZCX2-EW-QN204, and the Special Scientific Research Project for Public Interest Grant GYHY201006021. TL was supported by ONR Grants N000140810256 and N000141210450 and JAMSTEC/NOAA/NASA. This is SOEST contribution number 8914 and IPRC contribution number 974.


  1. Aiyyer AR, Molinari J (2003) Evolution of mixed Rossby-gravity waves in idealized MJO environments. J Atmos Sci 60:2837–2855CrossRefGoogle Scholar
  2. Camargo SJ, Sobel AH (2005) Western North Pacific tropical cyclone intensity and ENSO. J Clim 18:2996–3006CrossRefGoogle Scholar
  3. Camargo SJ, Emanuel KA, Sobel AH (2007) Use of a genesis potential index to diagnose ENSO effects on tropical cyclone genesis. J Clim 20:4819–4834CrossRefGoogle Scholar
  4. Chang H-R, Webster PJ (1990) Energy accumulation and emanation at low latitudes. Part II: nonlinear response to strong episodic equatorial forcing. J Atmos Sci 47:2624–2644CrossRefGoogle Scholar
  5. Chang H-R, Webster PJ (1995) Energy accumulation and emanation at low latitudes. Part III: forward and backward accumulation. J Atmos Sci 52:2384–2403CrossRefGoogle Scholar
  6. Chen G, Huang R (2009) Interannual variations in mixed Rossby–gravity waves and their impacts on tropical cyclogenesis over the Western North Pacific. J Clim 22:535–549CrossRefGoogle Scholar
  7. Chen T-C, Weng SP, Yamazaki N, Kiehne S (1998) Interannual variation in the tropical cyclone formation over the Western North Pacific. Mon Weather Rev 126:1080–1090CrossRefGoogle Scholar
  8. Chia HH, Ropelewski CF (2002) The interannual variability in the genesis location of tropical cyclones in the Northwest Pacific. J Clim 15:2934–2944CrossRefGoogle Scholar
  9. Clark JD, Chu P-S (2002) Interannual variation of tropical cyclone activity over the central North Pacific. J Meteor Soc Jpn 80:403–418CrossRefGoogle Scholar
  10. Dickinson M, Molinari J (2002) Mixed Rossby–gravity waves and western Pacific tropical cyclogenesis. Part I: synoptic evolution. J Atmos Sci 59:2183–2195CrossRefGoogle Scholar
  11. Frank WM, Roundy PE (2006) The role of tropical waves in tropical cyclogenesis. Mon Weather Rev 134:2397–2417CrossRefGoogle Scholar
  12. Fu B, Li T, Peng M, Weng F (2007) Analysis of tropical cyclone genesis in the western North Pacific for 2000 and 2001. Weather Forecast 22:763–780CrossRefGoogle Scholar
  13. Gall JS, Frank WM (2010) The role of equatorial Rossby waves in tropical cyclogenesis. Part II: idealized simulations in a monsoon trough environment. Mon Weather Rev 138:1383–1398CrossRefGoogle Scholar
  14. Gall JS, Frank WM, Wheeler MC (2010) The role of equatorial Rossby waves in tropical cyclogenesis. Part I: idealized numerical simulations in an initially quiescent background environment. Mon Weather Rev 138:1368–1382CrossRefGoogle Scholar
  15. Gu G, Zhang C (2008) A space-time wavelet spectrum analysis and its application to tropical atmospheric waves/oscillations. Curr Dev Theor Appl Wavelets 2(2):125–136Google Scholar
  16. Hendon HH, Wheeler MC (2008) Some space-time spectral analyses of tropical convection and planetary-scale waves. J Atmos Sci 65:2936–2948CrossRefGoogle Scholar
  17. Iizuka S, Matsuura T (2008) ENSO and Western North Pacific tropical cyclone activity simulated in a CGCM. Clim Dyn 30:815–830CrossRefGoogle Scholar
  18. Kanamitsu M, Ebisuzaki W, Woollen J, Yang S-K, Hnilo JJ, Fiorino M, Potter GL (2002) NCEP–DOE AMIP-II Reanalysis (R-2). Bull Am Meteor Soc 83:1631–1643CrossRefGoogle Scholar
  19. Lau K-H, Lau N-C (1990) Observed structure and propagation characteristics of tropical summertime synoptic scale disturbances. Mon Weather Rev 118:1888–1913CrossRefGoogle Scholar
  20. Li T (2006) Origin of the summertime synoptic-scale wave train in the western North Pacific. J Atmos Sci 63:1093–1102CrossRefGoogle Scholar
  21. Li T (2012) Synoptic and climatic aspects of tropical cyclogenesis in western North Pacific. In: Oouchi K, Fudevasu H (eds) Cyclones: formation, triggers and control. Noval Science Publishers, ISBN: 798-1-61942-976-5, pp 61–94Google Scholar
  22. Li T, Fu B (2006) Tropical cyclogenesis associated with Rossby wave energy dispersion of a pre-existing typhoon. Part I: satellite data analyses. J Atmos Sci 63:1377–1389CrossRefGoogle Scholar
  23. Li T, Fu B, Ge X, Wang B, Peng M (2003) Satellite data analysis and numerical simulation of tropical cyclone formation. Geophys Res Lett 30:2122–2126CrossRefGoogle Scholar
  24. Li T, Ge X, Wang B, Zhu Y (2006) Tropical cyclogenesis associated with Rossby wave energy dispersion of a pre-existing typhoon. Part II: numerical simulations. J Atmos Sci 63:1390–1409CrossRefGoogle Scholar
  25. Liebmann B, Smith CA (1996) Description of a complete (interpolated) OLR dataset. Bull Am Meteor Soc 77:1275–1277Google Scholar
  26. Maloney ED, Hartmann DL (2001) The Madden–Julian oscillation, barotropic dynamics, and North Pacific tropical cyclone formation. Part I: Observations. J Atmos Sci 58:2545–2558CrossRefGoogle Scholar
  27. Molinari J, Lombardo K, Vollaro D (2007) Tropical cyclogenesis within an equatorial Rossby wave packet. J Atmos Sci 64:1301–1317CrossRefGoogle Scholar
  28. Roundy PE, Frank WM (2004) A climatology of waves in the equatorial region. J Atmos Sci 61:2105–2132CrossRefGoogle Scholar
  29. Sobel AH, Bretherton CS (1999) Development of synoptic-scale disturbances over the summertime tropical Northwest Pacific. J Atmos Sci 56:3106–3127CrossRefGoogle Scholar
  30. Sobel AH, Maloney ED (2000) Effect of ENSO and the MJO on western North Pacific tropical cyclones. Geophys Res Lett 27:1739–1742CrossRefGoogle Scholar
  31. Takayabu YN, Nitta T (1993) 3–5 day period disturbances coupled with convection over the tropical Pacific Ocean. J Meteor Soc Jpn 71:221–246Google Scholar
  32. Tam C-Y, Li T (2006) The origin and dispersion characteristics of the observed tropical summertime synoptic-scale waves over the western Pacific. Mon Weather Rev 134:1630–1646CrossRefGoogle Scholar
  33. Wang B, Chan JC-L (2002) How strong ENSO events affect tropical storm activity over the Western North Pacific. J Clim 15:1643–1658CrossRefGoogle Scholar
  34. Webster PJ, Chang H-R (1988) Equatorial energy accumulation and emanation regions: impact of a zonally varying basic state. J Atmos Sci 45:803–829CrossRefGoogle Scholar
  35. Wheeler M, Kiladis GN (1999) Convectively coupled equatorial waves: analysis of clouds and temperature in the wavenumber-frequency domain. J Atmos Sci 56:374–399CrossRefGoogle Scholar
  36. Wu L, Wang B (2004) Assessing impacts of global warming on tropical cyclone tracks. J Clim 17:1686–1698CrossRefGoogle Scholar
  37. Wu L, Wen Z, Huang R, Wu R (2012) Possible linkage between the monsoon trough variability and the tropical cyclone activity over the Western North Pacific. Mon Weather Rev 140:140–150CrossRefGoogle Scholar
  38. Zehr RM (1992) Tropical cyclogenesis in the western north Pacific. In: NOAA Technical Report NESDIS 61. US Dept of Commerce, Washington DCGoogle Scholar
  39. Zhou X, Wang B (2007) Transition from an eastern Pacific upper-level mixed Rossby-gravity wave to a western Pacific tropical cyclone. Geophys Res Lett 34:L24801CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  1. 1.Center for Monsoon System Research, Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina
  2. 2.Center for Monsoon and Environment Research/Department of Atmospheric SciencesSun Yat-sen UniversityGuangzhouChina
  3. 3.International Pacific Research Center and Department of Meteorology, School of Ocean and Earth Science and TechnologyUniversity of Hawaii at ManoaHonoluluHawaii

Personalised recommendations