Spectrum analysis of easterly waves in the tropical Pacific during two contrasting periods of sea-surface temperature anomalies
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Authors
Chang, C.-P.
Miller, Charles Robert
Subjects
tropical meteorology
tropical waves
easterly waves
sea-surface temperature anomalies.
tropical waves
easterly waves
sea-surface temperature anomalies.
Advisors
Date of Issue
1976-07
Date
1976-07
Publisher
Monterey, California. Naval Postgraduate School
Language
en_US
Abstract
The structure and properties of the tropical easterly waves has been found to vary considerably between different regimes and time periods. This study investigates the possible roles played by the temporal and spatial sea-surface temperature (SST) variations on the waves. Time series of tropical western pacific radiosonde data during two contrasting eight-month periods of SST anomalies, May-December 1972, which has abnormally high SST in the central and eastern Pacific, and May-December 1973 which has below normal SST in the same region, are analyzed. In both periods, the waves have the same periodicity of 4-5 days and a lower tropospheric zonal wavelength on the order of 3300 km, but their vertical phase and amplitude distributions as well as the thermal structures are different. The results are discussed in terms of two possible influences the SST variations may have on the waves: 1) direct effect, the warmer SST represents stronger thermal control through cumulus heating; and 2) indirect effect, the variation of SST changes the large-scale mean wind circulation which, in turn, has a strong impact on the wave vertical structure and the relative importance of energy sources other than cumulus heating. Finally, a schematic model of these influences is proposed which may be applied to both the temporal and the spatial variations of SST
Type
Technical Report
Description
Series/Report No
Department
Identifiers
NPS Report Number
NPS-63Cj76071
Sponsors
Prepared for: National Environmental Satellite Service, National Oceanic and Atmospheric Administration, Washington, D. C. 20233
Funder
Format
46 p. : ill. ; 28 cm.
Citation
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.