The role of the halted baroclinic mode at the central equatorial Pacific in El Nino event
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Authors
Sun, J.l.
Qinyu, Liu
Chu, Peter C.
Subjects
halted baroclinic mode
central equatorial Pacific
staged atmosphere-ocean interaction mechanism
El Nino
central equatorial Pacific
staged atmosphere-ocean interaction mechanism
El Nino
Advisors
Date of Issue
2005
Date
2005
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Abstract
The role of halted “baroclinic modes” in the central equatorial Pacific is analyzed. It is found that dominant anomaly signals corresponding to “baroclinic modes” occur in the upper layer of the equatorial Pacific, in a two-and-a-half layer oceanic model, in assimilated results of a simple OGCM and in the ADCP observation of TAO. A second “baroclinic mode” is halted in the central equatorial Pacific corresponding
to a positive SST anomaly while the first “baroclinic mode” propagates eastwards in the eastern equatorial Pacific. The role of the halted second “baroclinic mode” in the central equatorial Pacific is explained by a staged ocean-atmosphere interaction mechanism in the formation of El Nino: the westerly bursts in boreal winter over the western equatorial Pacific generate the halted second “baroclinic mode” in the central equatorial Pacific, leading to the increase of heat content and temperature in the upper layer of the
central Pacific which induces the shift of convection from over the western equatorial Pacific to the central equatorial Pacific; another wider, westerly anomaly burst is induced over the western region of convection above the central equatorial Pacific and the westerly anomaly burst generates the first “baroclinic mode” propagating to the eastern equatorial Pacific, resulting in a warm event in the eastern equatorial Pacific.
The mechanism presented in this paper reveals that the central equatorial Pacific is a key region in detecting the possibility of ENSO and, by analyzing TAO observation data of ocean currents and temperature in the central equatorial Pacific, in predicting the coming of an El Nino several months ahead.
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Article
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Advances in Atmospheric Sciences
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Oceanography
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Citation
Sun, J.l., P.C. Chu, and Q. Liu, 2006: The role of the halted baroclinic mode at the central equatorial Pacific in El Nino event (paper download). Advances in Atmospheric Sciences, Vol. 23, No. 1, 2005. pp. 45-53.
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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.