The Role of Atmospheric Teleconnection in the Subtropical Thermal Forcing on the Equatorial Pacific

WANG Lu; and YANG Haijun

doi:10.1007/s00376-013-3173-1

Abstract:

The equatorial response to subtropical Pacific forcing was studied in a coupled climate model. The forcings in the western, central and eastern subtropical Pacific all caused a significant response in the equatorial thermocline, with comparable magnitudes. This work highlights the key role of air-sea coupling in the subtropical impact on the equatorial thermocline, instead of only the role of the oceanic tunnel''. The suggested mechanism is that the cyclonic (anticyclonic) circulation in the atmosphere caused by the subtropical surface warming (cooling) can generate an anomalous upwelling (downwelling) in the interior region. At the same time, an anomalous downwelling (upwelling) occurs at the equatorward flank of the forcing, which produces anomalous thermocline warming (cooling), propagating equatorward and resulting in warming (cooling) in the equatorial thermocline. This is an indirect process that is much faster than the oceanic tunnel'' mechanism in the subtropical impact on the equator.

摘要: The equatorial response to subtropical Pacific forcing was studied in a coupled climate model. The forcings in the western, central and eastern subtropical Pacific all caused a significant response in the equatorial thermocline, with comparable magnitudes. This work highlights the key role of air-sea coupling in the subtropical impact on the equatorial thermocline, instead of only the role of the ``oceanic tunnel''. The suggested mechanism is that the cyclonic (anticyclonic) circulation in the atmosphere caused by the subtropical surface warming (cooling) can generate an anomalous upwelling (downwelling) in the interior region. At the same time, an anomalous downwelling (upwelling) occurs at the equatorward flank of the forcing, which produces anomalous thermocline warming (cooling), propagating equatorward and resulting in warming (cooling) in the equatorial thermocline. This is an indirect process that is much faster than the ``oceanic tunnel'' mechanism in the subtropical impact on the equator.

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The Role of Atmospheric Teleconnection in the Subtropical Thermal Forcing on the Equatorial Pacific

Corresponding author: WANG Lu;

1. Nuclear and Radiation Safety Center, Ministry of Environmental Protection of the People's Republic of China, Beijing 100082

2. Laboratory for Climate and Ocean-Atmosphere Studies and the Department of Atmospheric and Oceanic Sciences, Peking University, Beijing 100871

Manuscript received: 2013-09-02

Manuscript revised: 2013-11-20

Fund Project: This work was jointly supported by the National Natural Science Foundation of China (Grant Nos. 40976007, 41176002, and 41376007), the National Basic Research Program of China (Grant No. 2012CB955201), the Special Fund for Meteorological Scientific Research in the Public Interest of the China Meteorological Administration (Grant No. GYHY201006022), the Specialized Research Fund for the Doctoral Program of Higher Education of China (2010), and the Special Fund for Environmental Protection Scientific Research in the Public Interest of the Ministry of Environmental Protection of the People's Republic of China (Grant No. 201309056) The authors benefited from the invaluable comments of the two anonymous reviewers. All the experiments were carried out on the supercomputer at Peking University.

Abstract: The equatorial response to subtropical Pacific forcing was studied in a coupled climate model. The forcings in the western, central and eastern subtropical Pacific all caused a significant response in the equatorial thermocline, with comparable magnitudes. This work highlights the key role of air-sea coupling in the subtropical impact on the equatorial thermocline, instead of only the role of the oceanic tunnel''. The suggested mechanism is that the cyclonic (anticyclonic) circulation in the atmosphere caused by the subtropical surface warming (cooling) can generate an anomalous upwelling (downwelling) in the interior region. At the same time, an anomalous downwelling (upwelling) occurs at the equatorward flank of the forcing, which produces anomalous thermocline warming (cooling), propagating equatorward and resulting in warming (cooling) in the equatorial thermocline. This is an indirect process that is much faster than the oceanic tunnel'' mechanism in the subtropical impact on the equator.

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The Role of Atmospheric Teleconnection in the Subtropical Thermal Forcing on the Equatorial Pacific

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