TITLE

Modulation of South Indian Ocean Tropical Cyclones by the Madden–Julian Oscillation and Convectively Coupled Equatorial Waves

AUTHOR(S)
Bessafi, Miloud; Wheeler, Matthew C.
PUB. DATE
February 2006
SOURCE
Monthly Weather Review;Feb2006, Vol. 134 Issue 2, p638
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The subseasonal modulation of tropical cyclone (TC) genesis by large-scale atmospheric wave modes is studied using data from the south Indian Ocean region. The modes considered are the Madden–Julian oscillation (MJO), and the convectively coupled equatorial Rossby (ER), Kelvin, and mixed Rossby–gravity (MRG) waves. Analysis of all TCs west of 100°E reveals a large and statistically significant modulation by the MJO and ER waves, a small yet significant modulation by Kelvin waves, and a statistically insignificant modulation by MRG waves. Attribution of the observed TC modulation was made through examination of the wave-induced perturbations to the dynamical fields of low-level vorticity, vertical shear, and deep convection. Possible thermodynamic influences on TC genesis were neglected. Different combinations of the three dynamical fields were necessary for successful attribution for each of the large-scale wave modes. For example, for the MJO, the modulation was best attributable to its perturbations to both the vorticity and shear fields, while for the ER wave, it was its perturbations to the convection and vorticity fields that appeared to best be able to explain the modulation. It appears that there is no single factor that can be used for the attribution of all subseasonal TC variability. Finally, it is shown that the modulation of TCs by at least the MJO and ER waves is large enough to warrant further investigation for prediction on the weekly time scale.
ACCESSION #
19968141

 

Related Articles

  • Comments on “The Effect of Bottom Topography on the Speed of Long Extratropical Planetary Waves”. Tailleux, Rémi // Journal of Physical Oceanography;Jul2003, Vol. 33 Issue 7, p1536 

    Killworth and Blundell used the ray approach of Wentzel Kramers Bril-louin (WKB) theory to investigate the question of whether the large-scale topography could by itself speed up the long extratropical planetary waves of linear standard flat-bottom theory in a way consistent with the...

  • Rossby Wave Ray Tracing in a Barotropic Divergent Atmosphere. Chungu Lu; Boyd, John P. // Journal of the Atmospheric Sciences;May2008, Vol. 65 Issue 5, p1679 

    The effects of divergence on low-frequency Rossby wave propagation are examined by using the two-dimensional Wentzel–Kramers–Brillouin (WKB) method and ray tracing in the framework of a linear barotropic dynamic system. The WKB analysis shows that the divergent wind decreases...

  • Large-scale, free Rossby waves in the atmosphere—an update. Madden, Roland A. // Tellus: Series A;Oct2007, Vol. 59 Issue 5, p571 

    The existence of free, or normal mode Rossby waves has been known for 50 yr. Studies have indicated that they can affect the large-scale flow in important ways; nevertheless there has been little written on them during the last decade. Here, evidence of their presence in a 40-yr record of...

  • The Effect of a Hadley Circulation on the Propagation and Reflection of Planetary Waves in a Simple One-Layer Model. Esler, J. Gavin; Polvani, Lorenzo M. // Journal of the Atmospheric Sciences;5/15/2000, Vol. 57 Issue 10, p1536 

    Presents information on a study which investigated the effect of a simple representation of the Hadley circulation on the propagation and nonlinear reflection of planetary-scale Rossby waves in the winter hemisphere. Extent of Hadley circulation's inhibition of nonlinear reflection; Description...

  • Some Effects of Truncation on Topographic Instability. Fyfe, John; Derome, Jacques // Atmosphere -- Ocean (Canadian Meteorological & Oceanographic Soc;Jun1987, Vol. 25 Issue 2, p159 

    The topographic stability of forced planetary waves in a β-channel is investigated using a barotropic model. The equilibrium forced waves are the result of the interaction of a constant mean zonal wind over finite-amplitude surface orography. Small-amplitude perturbations of the equilibrium...

  • Comment on invalid JWKB unstable solutions of combined inertial-Rossby waves. McKenzie, J. F. // Annales Geophysicae (09927689);Mar2012, Vol. 30 Issue 3, p571 

    The author comments on the use of Jeffreys-Wentzel-Kramers-Brillouin (JWKB) solutions to derive a wave structure equation. He says JWKB solutions exhibit complex roots for the wave frequency if the speed of the Rossby wave exceeded that of the higher frequency inertial wave speed. He offers...

  • The Nonlinear Interaction of Barotropic and Equatorial Baroclinic Rossby Waves. Majda, Andrew J.; Biello, Joseph A. // Journal of the Atmospheric Sciences;8/1/03, Vol. 60 Issue 15, p1809 

    Simplified asymptotic equations are developed for the nonlinear interaction of long-wavelength equatorial Rossby waves and barotropic Rossby waves with a significant midlatitude projection in the presence of suitable horizontally and vertically sheared zonal mean flows. The simplified equations...

  • Initially Forced Long Planetary Waves in the Presence of Nonzonal Mean Flow. Cerovečki, Ivana; de Szoeke, Roland A. // Journal of Physical Oceanography;Mar2006, Vol. 36 Issue 3, p507 

    The purpose of this paper is to understand how long planetary waves evolve when propagating in a subtropical gyre. The steady flow of a wind-driven vertically sheared model subtropical gyre is perturbed by Ekman pumping that is localized within a region of finite lateral extent and oscillates...

  • Extracting Envelopes of Nonzonally Propagating Rossby Wave Packets. Zimin, Aleksey V.; Szunyogh, Istvan; Hunt, Brian R.; Ott, Edward // Monthly Weather Review;Apr2006, Vol. 134 Issue 4, p1329 

    Previously developed techniques that have been used to extract envelopes of Rossby wave packets are based on the assumption of zonally propagating waves. In this note a method that does not require such an assumption is proposed. The advantages of the new technique, both on analytical and...

Share

Read the Article

Courtesy of THE LIBRARY OF VIRGINIA

Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics