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| A Premonitory Sign of Anomalous SSTs over the Eastern Equatorial Pacific and a Forecasting Experiment |
| ZHANG Qing-Yun,CHANG Rui |
| State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing；Center for Disastrous Climate Research and Prediction, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing,Center for Disastrous Climate Research and Prediction, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing |
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Abstract A premonitory sign of an anomalous SST over the eastern equatorial Pacific shows up in the North Pacific Subtropical Mode Water (STMW) 18 months earlier, and the air-sea relationship between the STMW and the anomalous SST over the eastern equatorial Pacific is shown. This premonitory connection involves an air-sea coupling between the longtime persistent mid-latitude sea surface temperature anomaly (SSTA) induced by the remote re-emergence of the STMW and the following spring subtropical atmospheric circulation anomalies. An examination of the air-sea interaction reveals that the following spring subtropical atmospheric circulation, which responds to the longtime persistent SSTA, is dominated by the anomalous negative (positive) geopotential height downstream of the negative (positive) SSTA in the strong (weak) STMW case. Thus, the tropics adjust to these anomalies through coupled dynamics, producing positive (negative) SST anomalies over the eastern equatorial Pacific. A cold water event that occurred over the eastern equatorial Pacific during winter 2008-09 was successfully forecasted by the weak summer STMW index in 2007. The evolution of this process for the air-sea interactions from the autumn of 2007 to December 2008 is presented.
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Received: 27 June 2009
Revised: 12 August 2009
Accepted: 13 August 2009
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