Differences between more divergent and more rotational types of convectively coupled equatorial waves. Part I

Space-time spectral analyses

Kazuaki Yasunaga, Brian E Mapes

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

Precipitation-related differences in different types of convectively coupled equatorial waves are examined here and in a companion paper. Here the authors show spectra and cross-spectra among tropical-belt time sections of satellite-derived surface rain, infrared brightness temperature T b, precipitable water (PW), and Japan Meteorological Agency reanalysis of divergence and PW. Cross-spectra between rain and divergence at 1000- and 200-hPa levels show significant coherence peaks oriented along the dispersion curves of Kelvin, n 5 1 equatorial Rossby (ERn1), mixed Rossby-gravity (MRG), n50 eastward inertial gravity (EIGn0), and n51 and n 52 westward inertial gravity (WIG) waves, as well as the spectral signatures of the Madden-Julian oscillation (MJO) and tropical depression (TD)-type disturbances. Middle-troposphere divergence (indicative of stratiform rain and half-depth convection involvement in the coupling) is coherent with rain for the higher-frequency and more divergent wave types (Kelvin, EIGn0, WIG) but shows little coherence with rain for more rotational disturbance types (ERn1, MRG, TD). These two broad families also exhibit different rain-PW phase lags, a result supportive of the notion that stratiform rain (which occurs in dry conditions after peak PW and rain) is more involved in the more divergent wave types.

Original languageEnglish (US)
Pages (from-to)3-16
Number of pages14
JournalJournal of the Atmospheric Sciences
Volume69
Issue number1
DOIs
StatePublished - Jan 2012

Fingerprint

equatorial wave
precipitable water
gravity
divergence
disturbance
Madden-Julian oscillation
rain
brightness temperature
gravity wave
troposphere
convection

Keywords

  • Convection
  • Inertia-gravity waves
  • Kelvin waves
  • Rossby waves
  • Tropics

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

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abstract = "Precipitation-related differences in different types of convectively coupled equatorial waves are examined here and in a companion paper. Here the authors show spectra and cross-spectra among tropical-belt time sections of satellite-derived surface rain, infrared brightness temperature T b, precipitable water (PW), and Japan Meteorological Agency reanalysis of divergence and PW. Cross-spectra between rain and divergence at 1000- and 200-hPa levels show significant coherence peaks oriented along the dispersion curves of Kelvin, n 5 1 equatorial Rossby (ERn1), mixed Rossby-gravity (MRG), n50 eastward inertial gravity (EIGn0), and n51 and n 52 westward inertial gravity (WIG) waves, as well as the spectral signatures of the Madden-Julian oscillation (MJO) and tropical depression (TD)-type disturbances. Middle-troposphere divergence (indicative of stratiform rain and half-depth convection involvement in the coupling) is coherent with rain for the higher-frequency and more divergent wave types (Kelvin, EIGn0, WIG) but shows little coherence with rain for more rotational disturbance types (ERn1, MRG, TD). These two broad families also exhibit different rain-PW phase lags, a result supportive of the notion that stratiform rain (which occurs in dry conditions after peak PW and rain) is more involved in the more divergent wave types.",
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AB - Precipitation-related differences in different types of convectively coupled equatorial waves are examined here and in a companion paper. Here the authors show spectra and cross-spectra among tropical-belt time sections of satellite-derived surface rain, infrared brightness temperature T b, precipitable water (PW), and Japan Meteorological Agency reanalysis of divergence and PW. Cross-spectra between rain and divergence at 1000- and 200-hPa levels show significant coherence peaks oriented along the dispersion curves of Kelvin, n 5 1 equatorial Rossby (ERn1), mixed Rossby-gravity (MRG), n50 eastward inertial gravity (EIGn0), and n51 and n 52 westward inertial gravity (WIG) waves, as well as the spectral signatures of the Madden-Julian oscillation (MJO) and tropical depression (TD)-type disturbances. Middle-troposphere divergence (indicative of stratiform rain and half-depth convection involvement in the coupling) is coherent with rain for the higher-frequency and more divergent wave types (Kelvin, EIGn0, WIG) but shows little coherence with rain for more rotational disturbance types (ERn1, MRG, TD). These two broad families also exhibit different rain-PW phase lags, a result supportive of the notion that stratiform rain (which occurs in dry conditions after peak PW and rain) is more involved in the more divergent wave types.

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