Response of equatorial Pacific upper ocean current to westerly wind bursts

1995 ◽  
Vol 13 (4) ◽  
pp. 294-302
Author(s):  
Wang Fan ◽  
Wu De-xing ◽  
She Guo-hui ◽  
Yan Ji-qiao
Keyword(s):  
Equatorial Pacific ◽  
Ocean Current ◽  
Upper Ocean ◽  
Westerly Wind ◽  
Wind Bursts ◽  
Westerly Wind Bursts

Effects of westerly wind bursts upon the western equatorial Pacific Ocean, February–April 1991

1993 ◽  
Vol 98 (C9) ◽  
pp. 16379 ◽  
Author(s):  
Thierry Delcroix ◽  
Gérard Eldin ◽  
Michael McPhaden ◽  
Alain Morlière
Keyword(s):  
Pacific Ocean ◽  
Equatorial Pacific ◽  
Westerly Wind ◽  
Equatorial Pacific Ocean ◽  
Western Equatorial Pacific ◽  
Wind Bursts ◽  
Westerly Wind Bursts

The response of the western equatorial Pacific Ocean to westerly wind bursts during November 1989 to January 1990

1992 ◽  
Vol 97 (C9) ◽  
pp. 14289 ◽  
Author(s):  
M. J. McPhaden ◽  
F. Bahr ◽  
Y. Du Penhoat ◽  
E. Firing ◽  
S. P. Hayes ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Equatorial Pacific ◽  
Westerly Wind ◽  
Equatorial Pacific Ocean ◽  
Western Equatorial Pacific ◽  
Wind Bursts ◽  
Westerly Wind Bursts

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.

scholarly journals Intraseasonal Variability of Equatorial Indian Ocean Zonal Currents

2007 ◽  
Vol 20 (13) ◽  
pp. 3036-3055 ◽  
Author(s):  
Debasis Sengupta ◽  
Retish Senan ◽  
B. N. Goswami ◽  
Jérôme Vialard
Keyword(s):  
Indian Ocean ◽  
Wind Stress ◽  
Equatorial Indian Ocean ◽  
Ocean Current ◽  
Upper Ocean ◽  
Thermocline Depth ◽  
Westerly Wind ◽  
Pressure Force ◽  
Easterly Wind ◽  
Wind Bursts

Abstract New satellite and in situ observations show large intraseasonal (10–60 day) variability of surface winds and upper-ocean current in the equatorial Indian Ocean, particularly in the east. An ocean model forced by the Quick Scatterometer (QuikSCAT) wind stress is used to study the dynamics of the intraseasonal zonal current. The model has realistic upper-ocean currents and thermocline depth variabilities on intraseasonal to interannual scales. The quality of the simulation is directly attributed to the accuracy of the wind forcing. At the equator, moderate westerly winds are punctuated by strong 10–40-day westerly wind bursts. The wind bursts force swift, intraseasonal (20–50 day) eastward equatorial jets in spring, summer, and fall. The zonal momentum balance is between local acceleration, stress, and pressure, while nonlinearity deepens and strengthens the eastward current. The westward pressure force associated with the thermocline deepening toward the east rapidly arrests eastward jets and, subsequently, generates (weak) westward flow. Thus, in accord with direct observations in the east, the spring jet is a single intraseasonal event, there are intraseasonal jets in summer, and the fall jet is long lived but strongly modulated on an intraseasonal scale. The zonal pressure force is almost always westward in the upper 120 m, and changes sign twice a year in the 120–200-m layer. Transient eastward equatorial undercurrents in early spring and late summer are associated with semiannual Rossby waves generated at the eastern boundary following thermocline deepening by the spring and fall jets. An easterly wind stress is not necessary to generate the undercurrents. Experiments with a single westerly wind burst forcing show that apart from the intraseasonal response, the zonal pressure force and current in the east have an intrinsic 90-day time scale that arises purely from equatorial adjustment.

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