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    Large-Scale Dynamical Fields Associated with Convectively Coupled Equatorial Waves

    Source: Journal of the Atmospheric Sciences:;2000:;Volume( 057 ):;issue: 005::page 613
    Author:
    Wheeler, Matthew
    ,
    Kiladis, George N.
    ,
    Webster, Peter J.
    DOI: 10.1175/1520-0469(2000)057<0613:LSDFAW>2.0.CO;2
    Publisher: American Meteorological Society
    Abstract: Convectively coupled equatorial waves, as previously detected in studies of wavenumber-frequency spectra of tropical clouds, are studied in more detail. Composite dynamical structures of the waves are obtained using linear regression between selectively filtered satellite-observed outgoing longwave radiation (OLR) data, and various fields from a global reanalysis dataset. The selective filtering of the OLR was designed to isolate the convective variations contributing to spectral peaks that lie along the equatorial wave dispersion curves for equivalent depths in the range of 12?50 m. The waves studied are the Kelvin, n = 1 equatorial Rossby (ER), mixed Rossby?gravity, n = 0 eastward inertio?gravity, n = 1 westward inertio?gravity (WIG), and n = 2 WIG waves. The horizontal structures of the dynamical fields associated with the waves are all generally consistent with those calculated from inviscid equatorial ?-plane shallow water theory. In the vertical, there are statistically significant structures spanning the depth of the troposphere, and for all but the ER wave there are associated vertically propagating signals extending into the equatorial stratosphere as well. In zonal cross sections, the vertical structure of the temperature anomaly field appears, for all but the ER wave, as a ?boomerang?-like shape, with the ?elbow? of the boomerang occurring consistently at the 250-hPa level. The tilts of the boomerang imply upward phase propagation throughout most of the troposphere, and downward phase propagation above. The deep convection of the waves occurs in regions of anomalously cold temperatures in the lower troposphere, warm temperatures in the upper troposphere, and cold temperatures at the level of the tropopause. Such a vertical structure appears to indicate that waves of relatively short vertical wavelengths (Lz ? 10 km) are indeed important for the coupling of large-scale dynamics and convection. The deeper structure of the convectively coupled ER wave, on the other hand, is thought to be an indication of the effects of basic-state vertical shear. Finally, the scales of the waves in the equatorial lower stratosphere that are forced by the convectively coupled equatorial waves are quite consistent with those found in many previous studies.
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      Large-Scale Dynamical Fields Associated with Convectively Coupled Equatorial Waves

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    http://yetl.yabesh.ir/yetl1/handle/yetl/4159010
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    • Journal of the Atmospheric Sciences

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    contributor authorWheeler, Matthew
    contributor authorKiladis, George N.
    contributor authorWebster, Peter J.
    date accessioned2017-06-09T14:36:00Z
    date available2017-06-09T14:36:00Z
    date copyright2000/03/01
    date issued2000
    identifier issn0022-4928
    identifier otherams-22548.pdf
    identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4159010
    description abstractConvectively coupled equatorial waves, as previously detected in studies of wavenumber-frequency spectra of tropical clouds, are studied in more detail. Composite dynamical structures of the waves are obtained using linear regression between selectively filtered satellite-observed outgoing longwave radiation (OLR) data, and various fields from a global reanalysis dataset. The selective filtering of the OLR was designed to isolate the convective variations contributing to spectral peaks that lie along the equatorial wave dispersion curves for equivalent depths in the range of 12?50 m. The waves studied are the Kelvin, n = 1 equatorial Rossby (ER), mixed Rossby?gravity, n = 0 eastward inertio?gravity, n = 1 westward inertio?gravity (WIG), and n = 2 WIG waves. The horizontal structures of the dynamical fields associated with the waves are all generally consistent with those calculated from inviscid equatorial ?-plane shallow water theory. In the vertical, there are statistically significant structures spanning the depth of the troposphere, and for all but the ER wave there are associated vertically propagating signals extending into the equatorial stratosphere as well. In zonal cross sections, the vertical structure of the temperature anomaly field appears, for all but the ER wave, as a ?boomerang?-like shape, with the ?elbow? of the boomerang occurring consistently at the 250-hPa level. The tilts of the boomerang imply upward phase propagation throughout most of the troposphere, and downward phase propagation above. The deep convection of the waves occurs in regions of anomalously cold temperatures in the lower troposphere, warm temperatures in the upper troposphere, and cold temperatures at the level of the tropopause. Such a vertical structure appears to indicate that waves of relatively short vertical wavelengths (Lz ? 10 km) are indeed important for the coupling of large-scale dynamics and convection. The deeper structure of the convectively coupled ER wave, on the other hand, is thought to be an indication of the effects of basic-state vertical shear. Finally, the scales of the waves in the equatorial lower stratosphere that are forced by the convectively coupled equatorial waves are quite consistent with those found in many previous studies.
    publisherAmerican Meteorological Society
    titleLarge-Scale Dynamical Fields Associated with Convectively Coupled Equatorial Waves
    typeJournal Paper
    journal volume57
    journal issue5
    journal titleJournal of the Atmospheric Sciences
    identifier doi10.1175/1520-0469(2000)057<0613:LSDFAW>2.0.CO;2
    journal fristpage613
    journal lastpage640
    treeJournal of the Atmospheric Sciences:;2000:;Volume( 057 ):;issue: 005
    contenttypeFulltext
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    DSpace software copyright © 2002-2015  DuraSpace
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