Projection of Tropical Cyclones on Wavenumber–Frequency-Filtered Equatorial Waves

Anantha Aiyyer Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina

Search for other papers by Anantha Aiyyer in
Current site
Google Scholar
PubMed
Close
,
Ademe Mekonnen Department of Energy and Environmental Systems, North Carolina A&T University, Greensboro, North Carolina

Search for other papers by Ademe Mekonnen in
Current site
Google Scholar
PubMed
Close
, and
Carl J. Schreck III Cooperative Institute for Climate and Satellites, North Carolina State University, and NOAA/National Climatic Data Center, Asheville, North Carolina

Search for other papers by Carl J. Schreck III in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

The impact of localized convection associated with tropical cyclones (TCs) on activity ascribed to equatorial waves is estimated. An algorithm is used to remove outgoing longwave radiation (OLR) signal in the vicinity of observed tropical cyclones, and equatorial wave modes are extracted using the standard wavenumber–frequency decomposition method. The results suggest that climatological activity of convection-coupled equatorial waves is overestimated where TC tracks are densest. The greatest impact is found for equatorial Rossby (ER)- and tropical depression (TD)-type waves followed by the Madden–Julian oscillation (MJO). The basins most affected are the eastern and western North Pacific Ocean where, on average, TCs may contribute up to 10%–15% of the climatological wave amplitude variance in these modes. In contrast, Kelvin waves are least impacted by the projection of TCs. The results are likely relevant for studies on the climatology of equatorial waves in observations and global climate model simulations and for those examining individual cases of TC genesis modulated by equatorial wave activity.

Corresponding author address: Anantha Aiyyer, Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Campus Box 8208, Raleigh, NC 27695. E-mail: aaiyyer@ncsu.edu

Abstract

The impact of localized convection associated with tropical cyclones (TCs) on activity ascribed to equatorial waves is estimated. An algorithm is used to remove outgoing longwave radiation (OLR) signal in the vicinity of observed tropical cyclones, and equatorial wave modes are extracted using the standard wavenumber–frequency decomposition method. The results suggest that climatological activity of convection-coupled equatorial waves is overestimated where TC tracks are densest. The greatest impact is found for equatorial Rossby (ER)- and tropical depression (TD)-type waves followed by the Madden–Julian oscillation (MJO). The basins most affected are the eastern and western North Pacific Ocean where, on average, TCs may contribute up to 10%–15% of the climatological wave amplitude variance in these modes. In contrast, Kelvin waves are least impacted by the projection of TCs. The results are likely relevant for studies on the climatology of equatorial waves in observations and global climate model simulations and for those examining individual cases of TC genesis modulated by equatorial wave activity.

Corresponding author address: Anantha Aiyyer, Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Campus Box 8208, Raleigh, NC 27695. E-mail: aaiyyer@ncsu.edu
Save
  • 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
  • Bessafi, M., and M. C. Wheeler, 2006: Modulation of south Indian Ocean tropical cyclones by the Madden–Julian oscillation and convectively coupled equatorial waves. Mon. Wea. Rev., 134, 638656.

    • Search Google Scholar
    • Export Citation
  • Camargo, S. J., M. Wheeler, and A. Sobel, 2009: Diagnosis of the MJO modulation of tropical cyclogenesis using an empirical index. J. Atmos. Sci., 66, 30613074.

    • Search Google Scholar
    • Export Citation
  • Frank, W. M., and P. E. Roundy, 2004: A climatology of waves in the equatorial region. J. Atmos. Sci., 61, 21052132.

  • Frank, W. M., and P. E. Roundy, 2006: The role of tropical waves in tropical cyclogenesis. Mon. Wea. Rev., 134, 23972417.

  • Fu, B., T. Li, M. Peng, and F. Weng, 2007: Analysis of tropical cyclone genesis in the western North Pacific for 2000 and 2001. Mon. Wea. Rev., 135, 763780.

    • Search Google Scholar
    • Export Citation
  • Gruber, A., 1974: The wavenumber-frequency spectra of satellite-measured brightness in the tropics. J. Atmos. Sci., 31, 16751680.

  • Hartmann, D. L., and E. D. Maloney, 2001: The Madden–Julian oscillation, barotropic dynamics, and North Pacific tropical cyclone formation. Part II: Stochastic barotropic modeling. J. Atmos. Sci., 58, 25592570.

    • Search Google Scholar
    • Export Citation
  • Knapp, K. R., M. C. Kruk, and D. H. Levinson, 2010: The International Best Track Archive for Climate Stewardship (IBTrACS). Bull. Amer. Meteor. Soc., 91, 363376.

    • Search Google Scholar
    • Export Citation
  • Liebmann, B., H. H. Hendon, and J. D. Glick, 1994: The relationship between tropical cyclones of the western Pacific and Indian Oceans and the Madden-Julian oscillation. J. Meteor. Soc. Japan, 72, 401412.

    • Search Google Scholar
    • Export Citation
  • Lin, J.-L., M. Zhang, and B. Mapes, 2005: Zonal momentum budget of the Madden–Julian oscillation: The source and strength of equivalent linear damping. J. Atmos. Sci., 62, 21722188.

    • Search Google Scholar
    • Export Citation
  • Molinari, J., K. Lombardo, D. Vollaro, and S. Skubis, 2007: Potential vorticity, easterly waves, and eastern Pacific tropical cyclogenesis. J. Atmos. Sci., 64, 13011317.

    • Search Google Scholar
    • Export Citation
  • Schreck, C., and J. Molinari, 2009: A case study of an outbreak of twin tropical cyclones. Mon. Wea. Rev., 137, 863875.

  • Schreck, C., J. Molinari, and K. Mohr, 2011: Attributing tropical cyclogenesis to equatorial waves in the western North Pacific. J. Atmos. Sci., 68, 195209.

    • Search Google Scholar
    • Export Citation
  • Takayabu, Y. N., 1994: Large-scale cloud disturbances associated with equatorial waves. Part I: Spectral features of the cloud disturbances. J. Meteor. Soc. Japan, 72, 433448.

    • Search Google Scholar
    • Export Citation
  • Wheeler, M., and G. N. Kiladis, 1999: Convectively couple equatorial waves: Analysis of clouds and temperature in the wavenumber–frequency domain. J. Atmos. Sci., 56, 374399.

    • Search Google Scholar
    • Export Citation
  • Wheeler, M., G. N. Kiladis, and P. J. Webster, 2000: Large-scale dynamical fields associated with equatorial waves. J. Atmos. Sci., 57, 613640.

    • Search Google Scholar
    • Export Citation
  • Yang, G., B. Hoskins, and J. Slingo, 2003: Convectively coupled equatorial waves: A new methodology for identifying wave structures in observational data. J. Atmos. Sci., 60, 16371654.

    • Search Google Scholar
    • Export Citation
  • Zangvil, A., 1975: Temporal and spatial behavior of large-scale disturbances in tropical cloudiness deduced from satellite brightness data. Mon. Wea. Rev., 103, 904920.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 412 157 5
PDF Downloads 303 115 7