The Heat Balance in the Western Equatorial Pacific Warm Pool during the Westerly Wind Bursts: A Case Study

2001 ◽  
Vol 18 (5) ◽  
pp. 882-896 ◽  
Author(s):  
Liu Hailong ◽  
Zhang Xuehong ◽  
Li Wei
Keyword(s):  
Heat Balance ◽  
Warm Pool ◽  
Equatorial Pacific ◽  
Westerly Wind ◽  
Pacific Warm Pool ◽  
Western Equatorial Pacific ◽  
Wind Bursts ◽  
The Heat Balance ◽  
Westerly Wind Bursts

scholarly journals Predictability of SST-Modulated Westerly Wind Bursts

2009 ◽  
Vol 22 (14) ◽  
pp. 3894-3909 ◽  
Author(s):  
Geoffrey Gebbie ◽  
Eli Tziperman
Keyword(s):  
Large Scale ◽  
Nonlinear Function ◽  
Warm Pool ◽  
Ensemble Prediction ◽  
Westerly Wind ◽  
Enso Dynamics ◽  
Pacific Warm Pool ◽  
Ensemble Mean ◽  
Wind Bursts ◽  
Westerly Wind Bursts

Abstract Westerly wind bursts (WWBs), a significant player in ENSO dynamics, are modeled using an observationally motivated statistical approach that relates the characteristics of WWBs to the large-scale sea surface temperature. Although the WWB wind stress at a given location may be a nonlinear function of SST, the characteristics of WWBs are well described as a linear function of SST. Over 50% of the interannual variance in the WWB likelihood, zonal location, duration, and fetch is explained by changes in SST. The model captures what is seen in a 17-yr record of satellite-derived winds: the eastward migration and increased occurrence of wind bursts as the western Pacific warm pool extends. The WWB model shows significant skill in predicting the interannual variability of the characteristics of WWBs, while the prediction skill of the WWB seasonal cycle is limited by the record length of available data. The novel formulation of the WWB model can be implemented in a stochastic or deterministic mode, where the deterministic mode predicts the ensemble-mean WWB characteristics. Therefore, the WWB model is especially appropriate for ensemble prediction experiments with existing ENSO models that are not capable of simulating realistic WWBs on their own. Should only the slowly varying component of WWBs be important for ENSO prediction, this WWB model allows a shortcut to directly compute the slowly varying ensemble-mean wind field without performing many realizations.

scholarly journals Westerly Wind Bursts: ENSO’s Tail Rather than the Dog?

2005 ◽  
Vol 18 (24) ◽  
pp. 5224-5238 ◽  
Author(s):  
Ian Eisenman ◽  
Lisan Yu ◽  
Eli Tziperman
Keyword(s):  
Large Scale ◽  
Warm Pool ◽  
Equatorial Pacific ◽  
Short Time Scale ◽  
Westerly Wind ◽  
Stochastic Forcing ◽  
Enso Events ◽  
Ocean Atmosphere ◽  
Wind Bursts ◽  
Westerly Wind Bursts

Abstract Westerly wind bursts (WWBs) in the equatorial Pacific occur during the development of most El Niño events and are believed to be a major factor in ENSO’s dynamics. Because of their short time scale, WWBs are normally considered part of a stochastic forcing of ENSO, completely external to the interannual ENSO variability. Recent observational studies, however, suggest that the occurrence and characteristics of WWBs may depend to some extent on the state of ENSO components, implying that WWBs, which force ENSO, are modulated by ENSO itself. Satellite and in situ observations are used here to show that WWBs are significantly more likely to occur when the warm pool is extended eastward. Based on these observations, WWBs are added to an intermediate complexity coupled ocean–atmosphere ENSO model. The representation of WWBs is idealized such that their occurrence is modulated by the warm pool extent. The resulting model run is compared with a run in which the WWBs are stochastically applied. The modulation of WWBs by ENSO results in an enhancement of the slow frequency component of the WWBs. This causes the amplitude of ENSO events forced by modulated WWBs to be twice as large as the amplitude of ENSO events forced by stochastic WWBs with the same amplitude and average frequency. Based on this result, it is suggested that the modulation of WWBs by the equatorial Pacific SST is a critical element of ENSO’s dynamics, and that WWBs should not be regarded as purely stochastic forcing. In the paradigm proposed here, WWBs are still an important aspect of ENSO’s dynamics, but they are treated as being partially stochastic and partially affected by the large-scale ENSO dynamics, rather than being completely external to ENSO. It is further shown that WWB modulation by the large-scale equatorial SST field is roughly equivalent to an increase in the ocean–atmosphere coupling strength, making the coupled equatorial Pacific effectively self-sustained.

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