Differences between faster versus slower components of convectively coupled equatorial waves

Kazuaki Yasunaga, Brian Mapes

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


This paper describes an analysis of multiyear satellite datasets that subdivide two halves (faster and slower) of the space-time spectral signal peaks corresponding to convectively coupled equatorial waves such as Kelvin and inertia-gravity waves [n 5 0 eastward inertia-gravity wave (EIGn0 wave), and n 5 1 and n 5 2 westward inertia-gravity waves (WIGn1 and WIGn2 waves, respectively)]. The faster (slower) component of an equatorial wave is defined as that which has a spectral signal peak in the regions with deeper (shallower) equivalent depths. The data obtained from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (TRMM-PR) are composited around space-time-filtered equatorial-belt data from the TRMM-3B42 rainfall product to separately estimate the convective and stratiform rainfall modulations. Results indicate that the faster components of WIGn1 and WIGn2 waves modulate convective rain relatively more (and stratiform rain relatively less) than their slower counterparts. For Kelvin and EIGn0 waves, however, there is no significant difference in the rainfall modulation between their faster and slower components. A space-time cospectral analysis of the satellite-retrieved rainfall and moisture shows that in the spectral regions corresponding toWIGn1 andWIGn2 waves, precipitation is significantly correlated with lowlevel moisture but not with midlevel moisture. In contrast, significant coherence between rainfall and moisture at these levels is found in the spectral regions corresponding to the Kelvin and EIGn0 waves. These results may bear on different convection-wave coupling mechanisms for these "divergent"waves (stratiform instability versus moisture-stratiform instability).

Original languageEnglish (US)
Pages (from-to)98-111
Number of pages14
JournalJournal of the Atmospheric Sciences
Issue number1
StatePublished - Jan 2014


  • Atmospheric
  • Convective clouds
  • Tropical variability
  • Waves

ASJC Scopus subject areas

  • Atmospheric Science


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