Analysis of Decadal Climate Variability in the Tropical Pacific by Coupled
GCM |
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Authors: | ZHANG Ya-Le and YU Yong-Qiang |
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Institution: | State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric
Physics (IAP), Chinese Academy of Sciences, Beijing 100029, China
Graduate University of the Chinese Academy of Sciences, Beijing 100049, China;State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric
Physics (IAP), Chinese Academy of Sciences, Beijing 100029, China |
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Abstract: | This study presents the spatial and temporal
structures of the decadal variability of the Pacific from an
extended control run of a coupled global climate model
(GCM). The GCM used was version g2.0 of the Flexible
Global Ocean Atmosphere Land System (FGOALS-g2.0)
developed at LASG/IAP. The GCM FGOALS-g2.0 reproduces
similar spatial-temporal structures of sea surface
temperature (SST) as observed in the Pacific decadal oscillation
(PDO) with a significant period of approximately
14 years. Correspondingly, the PDO signals were closely
related to the decadal change both in the upper-ocean
temperature anomalies and in the atmospheric circulation.
The present results suggest that warm SST anomalies
along the equator relax the trade winds, causing the SSTs
to warm even more in the eastern equatorial Pacific,
which is a positive feedback. Meanwhile, warm SST
anomalies along the equator force characteristic off-equatorial
wind stress curl anomalies, inducing much more
poleward transport of heat, which is a negative feedback.
The upper-ocean meridional heat transport, which is associated
with the PDO phase transition, links the equatorial
to the off-equatorial Pacific Ocean, acting as a major
mechanism responsible for the tropical Pacific decadal
variations. Therefore, the positive and negative feedbacks
working together eventually result in the decadal oscillation
in the Pacific. |
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Keywords: | Pacific decadal oscillation coupled GCM air-sea interaction meridional heat transport |
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