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Wyrtki Jets: Role of intraseasonal forcing

  • S PrernaEmail author
  • Abhisek Chatterjee
  • A Mukherjee
  • M Ravichandran
  • S S C Shenoi
Article
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Abstract

Direct current measurements observed from the acoustic Doppler current profilers in the equatorial Indian Ocean (EIO) and solutions from an ocean general circulation model are investigated to understand the dynamics of the Wyrtki jet. These jets are usually described as semiannual direct wind forced zonal currents along the central and eastern EIO. We show that both, spring and fall, Wyrtki jets show predominant semiannual spectral peaks, but significant intraseasonal energy is evident during spring in the central and eastern EIO. We find that for the semiannual band, there is a strong spectral coherence between the overlying winds and the currents in the central EIO, but no coherency is observed in the eastern part of the EIO. Moreover, for the intraseasonal band, strong coherency between the winds and currents is evident. During spring, intraseasonal currents induced by the Madden–Julian oscillation (MJO) superimpose constructively with semiannual currents and thus intensify the strength of the spring Wyrtki jet. Also, the atmospheric intraseasonal variability accounts for the interannual variabilities observed in spring Wyrtki jets.

Keywords

Indian Ocean equatorial dynamics MJO zonal currents 

Notes

Acknowledgements

All the MOM4p1 simulations were carried out on the INCOIS-HPC and on Aditya at IITM, Pune. Ferret is extensively used for analysis and graphics. The MJO index is downloaded from Australian Government Bureau of Meteorology (http://www.bom.gov.au/climate/mjo). Thanks to NOAA/CDC for the OLR data sets and NOAA/PMEL for the equatorial RAMA ADCP (http://www.pmel.noaa.gov/tao/data_deliv/deliv-nojava-rama.html) data sets. This is INCOIS contribution no. 321.

Supplementary material

12040_2018_1042_MOESM1_ESM.pdf (11.9 mb)
Supplementary material 1 (pdf 12152 KB)

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Copyright information

© Indian Academy of Sciences 2019

Authors and Affiliations

  • S Prerna
    • 1
    Email author
  • Abhisek Chatterjee
    • 1
  • A Mukherjee
    • 1
  • M Ravichandran
    • 2
  • S S C Shenoi
    • 1
  1. 1.Indian National Centre for Ocean Information ServicesHyderabadIndia
  2. 2.National Centre for Antarctic and Ocean ResearchGoaIndia

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