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SEASONAL VARIATIONS AND EXCITATION M...

LU, MONG-MING.

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SEASONAL VARIATIONS AND EXCITATION MECHANISMS OF THE EQUATORIALLY TRAPPED WAVES.

Record Type:	Electronic resources : Monograph/item
Title/Author:	SEASONAL VARIATIONS AND EXCITATION MECHANISMS OF THE EQUATORIALLY TRAPPED WAVES./
Author:	LU, MONG-MING.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 1987,
Description:	351 p.
Notes:	Source: Dissertations Abstracts International, Volume: 48-07, Section: B.
Contained By:	Dissertations Abstracts International48-07B.
Subject:	Atmosphere. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=8719932

SEASONAL VARIATIONS AND EXCITATION MECHANISMS OF THE EQUATORIALLY TRAPPED WAVES.
LU, MONG-MING.

SEASONAL VARIATIONS AND EXCITATION MECHANISMS OF THE EQUATORIALLY TRAPPED WAVES. - Ann Arbor : ProQuest Dissertations & Theses, 1987 - 351 p.

Source: Dissertations Abstracts International, Volume: 48-07, Section: B.

Thesis (Ph.D.)--University of California, Los Angeles, 1987.

This item must not be sold to any third party vendors.

The seasonal variation and excitation mechanisms of the equatorially trapped waves (ETWs) are studied using the wind, geopotential and outgoing longwave radiation (OLR) data during the First and Second Special Observing Periods (SOP-I and SOP-II) of the First GARP Global Experiment (FGGE). Some properties of the low-frequency (30-50 day) oscillation in the equatorial region are also examined. The intensity of equatorial disturbances in the wind field is found to be closely related to the configurations of the mean zonal flow. The maximum intensity appears in the region of westerly flow. The minimum appears in the region of easterly flow where intense cumulus convection is observed. The dominant zonal wavenumbers (s) and periods ($\au$) of ETWs are determined by examining the spectra of equatorial zonal and meridional winds. Kelvin waves with s = 1 and 2 and $\au$ = 7$-$10 days and mixed Rossby-gravity waves with s = 4$-$5 and $\au$ = 4$-$5 days are found in both SOPs. Additionally, the SOP-II, a Kelvin wave with S = 1 and $\au$ - 15$-$17 days and an eastward moving low-frequency zonal wind oscillation with s = 1 and $\au\\sim$ 30 days are observed. Both the spectral analysis of meridional wave energy flux (WEF) and the time series of the zonally averaged wave amplitude and meridional WEF show that the convergence of WEF between 14$\\sp\\circ$S and 14$\\sp\\circ$N is often associated with ETWs. Then, frequency band-pass filtering and zonal wavenumber decomposition are employed. The fast-moving Kelvin waves at 200 mb are always associated with some near-equatorial eddies. The convergence of WEF produced by these eddies appears to be crucial for exciting the Kelvin waves. The trough and ridge axes of mixed Rossby-gravity waves at 200 mb are tilted in such a way that these eddies transport wave energy meridionally. The amplitudes and the associated meridional WEF of the Kelvin waves are found to have the same longitudinal differences. In contrast, the convective activity and the amplitude of the Kelvin waves are negatively correlated. The Kelvin and mixed Rossby-gravity waves are found to be triggered or amplified by deep mid-oceanic troughs or by transient eddies located near the equator.Subjects--Topical Terms:

542821
Atmosphere.

SEASONAL VARIATIONS AND EXCITATION MECHANISMS OF THE EQUATORIALLY TRAPPED WAVES.
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100 1 $a LU, MONG-MING. $3 3558653
245 1 0 $a SEASONAL VARIATIONS AND EXCITATION MECHANISMS OF THE EQUATORIALLY TRAPPED WAVES.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 1987
300 $a 351 p.
500 $a Source: Dissertations Abstracts International, Volume: 48-07, Section: B.
500 $a Publisher info.: Dissertation/Thesis.
502 $a Thesis (Ph.D.)--University of California, Los Angeles, 1987.
506 $a This item must not be sold to any third party vendors.
506 $a This item must not be added to any third party search indexes.
520 $a The seasonal variation and excitation mechanisms of the equatorially trapped waves (ETWs) are studied using the wind, geopotential and outgoing longwave radiation (OLR) data during the First and Second Special Observing Periods (SOP-I and SOP-II) of the First GARP Global Experiment (FGGE). Some properties of the low-frequency (30-50 day) oscillation in the equatorial region are also examined. The intensity of equatorial disturbances in the wind field is found to be closely related to the configurations of the mean zonal flow. The maximum intensity appears in the region of westerly flow. The minimum appears in the region of easterly flow where intense cumulus convection is observed. The dominant zonal wavenumbers (s) and periods ($\au$) of ETWs are determined by examining the spectra of equatorial zonal and meridional winds. Kelvin waves with s = 1 and 2 and $\au$ = 7$-$10 days and mixed Rossby-gravity waves with s = 4$-$5 and $\au$ = 4$-$5 days are found in both SOPs. Additionally, the SOP-II, a Kelvin wave with S = 1 and $\au$ - 15$-$17 days and an eastward moving low-frequency zonal wind oscillation with s = 1 and $\au\\sim$ 30 days are observed. Both the spectral analysis of meridional wave energy flux (WEF) and the time series of the zonally averaged wave amplitude and meridional WEF show that the convergence of WEF between 14$\\sp\\circ$S and 14$\\sp\\circ$N is often associated with ETWs. Then, frequency band-pass filtering and zonal wavenumber decomposition are employed. The fast-moving Kelvin waves at 200 mb are always associated with some near-equatorial eddies. The convergence of WEF produced by these eddies appears to be crucial for exciting the Kelvin waves. The trough and ridge axes of mixed Rossby-gravity waves at 200 mb are tilted in such a way that these eddies transport wave energy meridionally. The amplitudes and the associated meridional WEF of the Kelvin waves are found to have the same longitudinal differences. In contrast, the convective activity and the amplitude of the Kelvin waves are negatively correlated. The Kelvin and mixed Rossby-gravity waves are found to be triggered or amplified by deep mid-oceanic troughs or by transient eddies located near the equator.
590 $a School code: 0031.
650 4 $a Atmosphere. $3 542821
690 $a 0725
710 2 $a University of California, Los Angeles. $3 626622
773 0 $t Dissertations Abstracts International $g 48-07B.
790 $a 0031
791 $a Ph.D.
792 $a 1987
793 $a English
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=8719932