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

Composite analysis based on space-time filtering

Kazuaki Yasunaga, Brian E Mapes

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

This paper describes an analysis of multiyear satellite datasets to characterize the modulations of convective versus stratiform rain, rain system size, and column water vapor by convectively coupled equatorial waves. Composites are built around space-time filtered equatorial-belt data from the Tropical Rainfall Measuring Mission (TRMM) 3B42 rainfall product, while TRMM Precipitation Radar (PR) and passive microwave data are the composited variables. The results are consistent with the more reanalysis-dependent findings in Part I, indicating that higher-frequency (or more divergent) waves, such as Kelvin and inertia- gravity families, modulate mesoscale convective systems and stratiform rain relatively more, whereas slower (or more rotational) types such as Rossby, mixed Rossby-gravity, and tropical depression (TD) or "easterly" waves primarily modulate convective rain and smaller-sized precipitation systems. Column water vapor composites indicate that the more rotational wave types modulate the moisture field more pronouncedly than do the divergent waves, leading the authors to speculate that the slow/rotational versus fast/wavelike distinction in precipitation characteristics may correspond to the different balances of two main convective coupling mechanisms: moisture control of cumulus cells versus convective inhibition control (via low-level density waves) of mesoscale convective systems. The Madden-Julian oscillation (MJO) is unique in that it exhibits prominent modulation of both stratiform precipitation (like the fast divergent waves) and small-sized precipitation features, convective rainfall, and moisture (like the other low-frequency, rotational waves). A composite of other waves' amplitudes as a function of MJO amplitude and phase shows that divergent waves are more active in the developing phase and rotational waves are more active in the decaying rather than developing phase of the MJO.

Original languageEnglish (US)
Pages (from-to)17-34
Number of pages18
JournalJournal of the Atmospheric Sciences
Volume69
Issue number1
DOIs
StatePublished - Jan 2012

Fingerprint

equatorial wave
Madden-Julian oscillation
convective system
TRMM
moisture
water vapor
gravity
easterly wave
analysis
rainfall
cumulus
inertia
radar
rain

Keywords

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

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

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title = "Differences between more divergent and more rotational types of convectively coupled equatorial waves. Part II: Composite analysis based on space-time filtering",
abstract = "This paper describes an analysis of multiyear satellite datasets to characterize the modulations of convective versus stratiform rain, rain system size, and column water vapor by convectively coupled equatorial waves. Composites are built around space-time filtered equatorial-belt data from the Tropical Rainfall Measuring Mission (TRMM) 3B42 rainfall product, while TRMM Precipitation Radar (PR) and passive microwave data are the composited variables. The results are consistent with the more reanalysis-dependent findings in Part I, indicating that higher-frequency (or more divergent) waves, such as Kelvin and inertia- gravity families, modulate mesoscale convective systems and stratiform rain relatively more, whereas slower (or more rotational) types such as Rossby, mixed Rossby-gravity, and tropical depression (TD) or {"}easterly{"} waves primarily modulate convective rain and smaller-sized precipitation systems. Column water vapor composites indicate that the more rotational wave types modulate the moisture field more pronouncedly than do the divergent waves, leading the authors to speculate that the slow/rotational versus fast/wavelike distinction in precipitation characteristics may correspond to the different balances of two main convective coupling mechanisms: moisture control of cumulus cells versus convective inhibition control (via low-level density waves) of mesoscale convective systems. The Madden-Julian oscillation (MJO) is unique in that it exhibits prominent modulation of both stratiform precipitation (like the fast divergent waves) and small-sized precipitation features, convective rainfall, and moisture (like the other low-frequency, rotational waves). A composite of other waves' amplitudes as a function of MJO amplitude and phase shows that divergent waves are more active in the developing phase and rotational waves are more active in the decaying rather than developing phase of the MJO.",
keywords = "Convection, Inertia-gravity waves, Kelvin waves, Rossby waves, Tropics",
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T1 - Differences between more divergent and more rotational types of convectively coupled equatorial waves. Part II

T2 - Composite analysis based on space-time filtering

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AU - Mapes, Brian E

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N2 - This paper describes an analysis of multiyear satellite datasets to characterize the modulations of convective versus stratiform rain, rain system size, and column water vapor by convectively coupled equatorial waves. Composites are built around space-time filtered equatorial-belt data from the Tropical Rainfall Measuring Mission (TRMM) 3B42 rainfall product, while TRMM Precipitation Radar (PR) and passive microwave data are the composited variables. The results are consistent with the more reanalysis-dependent findings in Part I, indicating that higher-frequency (or more divergent) waves, such as Kelvin and inertia- gravity families, modulate mesoscale convective systems and stratiform rain relatively more, whereas slower (or more rotational) types such as Rossby, mixed Rossby-gravity, and tropical depression (TD) or "easterly" waves primarily modulate convective rain and smaller-sized precipitation systems. Column water vapor composites indicate that the more rotational wave types modulate the moisture field more pronouncedly than do the divergent waves, leading the authors to speculate that the slow/rotational versus fast/wavelike distinction in precipitation characteristics may correspond to the different balances of two main convective coupling mechanisms: moisture control of cumulus cells versus convective inhibition control (via low-level density waves) of mesoscale convective systems. The Madden-Julian oscillation (MJO) is unique in that it exhibits prominent modulation of both stratiform precipitation (like the fast divergent waves) and small-sized precipitation features, convective rainfall, and moisture (like the other low-frequency, rotational waves). A composite of other waves' amplitudes as a function of MJO amplitude and phase shows that divergent waves are more active in the developing phase and rotational waves are more active in the decaying rather than developing phase of the MJO.

AB - This paper describes an analysis of multiyear satellite datasets to characterize the modulations of convective versus stratiform rain, rain system size, and column water vapor by convectively coupled equatorial waves. Composites are built around space-time filtered equatorial-belt data from the Tropical Rainfall Measuring Mission (TRMM) 3B42 rainfall product, while TRMM Precipitation Radar (PR) and passive microwave data are the composited variables. The results are consistent with the more reanalysis-dependent findings in Part I, indicating that higher-frequency (or more divergent) waves, such as Kelvin and inertia- gravity families, modulate mesoscale convective systems and stratiform rain relatively more, whereas slower (or more rotational) types such as Rossby, mixed Rossby-gravity, and tropical depression (TD) or "easterly" waves primarily modulate convective rain and smaller-sized precipitation systems. Column water vapor composites indicate that the more rotational wave types modulate the moisture field more pronouncedly than do the divergent waves, leading the authors to speculate that the slow/rotational versus fast/wavelike distinction in precipitation characteristics may correspond to the different balances of two main convective coupling mechanisms: moisture control of cumulus cells versus convective inhibition control (via low-level density waves) of mesoscale convective systems. The Madden-Julian oscillation (MJO) is unique in that it exhibits prominent modulation of both stratiform precipitation (like the fast divergent waves) and small-sized precipitation features, convective rainfall, and moisture (like the other low-frequency, rotational waves). A composite of other waves' amplitudes as a function of MJO amplitude and phase shows that divergent waves are more active in the developing phase and rotational waves are more active in the decaying rather than developing phase of the MJO.

KW - Convection

KW - Inertia-gravity waves

KW - Kelvin waves

KW - Rossby waves

KW - Tropics

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U2 - 10.1175/JAS-D-11-034.1

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EP - 34

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JF - Journals of the Atmospheric Sciences

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