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Observed variability in the upper layers at the Equator, 90°E in the Indian Ocean during 2001–2008, 2: meridional currents

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Abstract

In the Indian Ocean, the observed variability of meridional currents (MC) at the Equator, 90°E shows distinct 10–20 day (quasi-biweekly) north–south reversals in the near-surface 40–350 m water column. Unlike the zonal currents, the seasonal variability in the MC field is strikingly absent in the annual cycle over this water column. However, the strong amplitude oscillations penetrate deep during boreal winter, boreal spring and boreal fall seasons. There is also a suggestion that they are weak and shallow during summer monsoon season during the years when the intraseasonal zonal westerly wind bursts along the equator are weak or absent. These quasi-biweekly oscillations are attributed to the westward propagating equatorially trapped mixed Rossby-gravity (MRG) or Yanai waves triggered by the westward propagating meridional wind (MW) field along the equator suggesting a possibility of wind-forced response of the upper ocean. A careful examination reveals interannual modulation of this quasi-biweekly variability in the MC field. The salinity induced vertical stratification observed in the near-surface layer through barrier layer effects also shows a significant influence on the MC field on 10–20 day time scale. The upwelling and downwelling cycles caused in the near off-equatorial region as a result of the westward propagation of the MRG waves are noticed in the pycnocline inferred from the vertical temperature and salinity profiles recorded by a nearby TRITON CTD mooring deployed at 1.5°S, 90°E. The observed sharp differences in the MCs between years appear to be determined by the strengths of both MWs and barrier layer thickness. A suggestion of westward propagation of quasi-biweekly variability in SST along the equator with phase speed resembling that of the MRG waves is also episodically seen during most years.

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References

  • Akima H (1970) A new method of interpolation and smooth curve fitting based on local procedures. J Assoc Comput Mech 17:589–602

    Article  Google Scholar 

  • Blandford RR (1966) Mixed gravity-Rossby waves in the ocean. Deep-Sea Res 13:941–961

    Google Scholar 

  • Bleck R (2002) An oceanic general circulation model framed in hybrid isopycnic-Cartesian coordinates. Ocean Model 4:55–88

    Article  Google Scholar 

  • Chatterji P, Goswami BN (2004) Structure, genesis and scale selection of the tropical quasi-biweekly mode. Q J R Meteorol Soc 130(599):1171–1194

    Article  Google Scholar 

  • Chen TC, Chen JM (1993) The 10–20 day mode of the 1979 Indian Monsoon: its relation with the time variation of monsoon rainfall. Mon Weather Rev 121:2465–2482

    Article  Google Scholar 

  • Duchon CE (1979) Lanczos filter in one and two dimensions. J Appl Meteorol 18:1016–1022

    Article  Google Scholar 

  • Gill AE (1982) Atmosphere–ocean dynamics. Academic, San Diego

    Google Scholar 

  • Goswami BN, Sengupta D, Kumar S (1998) Intraseasonal oscillations and interannual variability of surface winds over the Indian monsoon region. Proc Ind Acad Sci 107(1):45–64

    Google Scholar 

  • Halkides DJ, Han W, Lee T, Masumoto Y (2007) Effects of sub-seasonal variability on seasonal-to-interannual Indian Ocean meridional heat transport. Geophys Res Lett 34:L12605. doi:10.1029/2007GL030150

    Article  Google Scholar 

  • Han W, Liu WT, Lin J (2006) Impact of submonthly oscillations on sea surface temperature of the tropical Indian Ocean. Geophys Res Lett 33:L03609. doi:10.1029/2005GL025082

    Google Scholar 

  • Hase H, Masumoto Y, Kuroda Y, Mizuno K (2008) Semiannual variability in temperature and salinity observed by Triangle Tans-Ocean Buoy Network (TRITON) buoys in the eastern tropical Indian Ocean. J Geophys Res 113:C01016. doi:10.1029/2006JC004026

    Article  Google Scholar 

  • Hino M (1977) Spectral analysis. Asakura-SyoTen, Tokyo (in Japanese)

    Google Scholar 

  • Johnson ES, Bonjean F, Lagerloef GSE, Gunn JT, Mitchum GT (2007) Validation and error analysis of OSCAR sea surface currents. J Ocean Atmos Technol 24(4):688–701

    Article  Google Scholar 

  • Kindle JC, Thompson JD (1989) The 26 and 30 day oscillation in the western Indian Ocean: model results. J Geophys Res 94:4721–4736

    Article  Google Scholar 

  • Knox R (1976) On a long series of measurements of Indian Ocean equatorial currents near Addu Atoll. Deep Sea Res 23:211–221

    Google Scholar 

  • Krishnamurti TN, Ardunay P (1980) The 10 to 20 day westward propagating mode and “breaks in the monsoons”. Tellus 32:15–26

    Google Scholar 

  • Kuroda Y (2002) TRITON: Present status and future plan. JAMSTEC Tech. Rep. TOCS 5, Japan Marine Science and Technology Center, Yokosuka, Japan

  • Lagerloef GSE, Mitchum GT, Lukas R, Niiler PP (1999) Tropical Pacific near surface currents estimated from altimeter, wind and drifter data. J Geophys Res 104:23313–23326

    Article  Google Scholar 

  • Loschnigg J, Webster P (2000) A coupled ocean–atmosphere system of SST modulation for the Indian Ocean. J Clim 13:3342–3360

    Article  Google Scholar 

  • Luyten JR, Roemmich DH (1982) Equatorial currents at semiannual period in the Indian Ocean. J Phys Oceanogr 12:406–413

    Article  Google Scholar 

  • Masumoto Y, Hase H, Kuroda Y, Matsuura H, Takeuchi K (2005) Intraseasonal variability in the upper layer currents observed in the eastern equatorial Indian Ocean. Geophys Res Lett 32:L02607. doi:10.1029/2004GL021896

    Article  Google Scholar 

  • Matsuno T (1966) Quasi-geostrophic motions in the equatorial area. J Meteorol Soc Jpn 44:25–43

    Article  Google Scholar 

  • McPhaden MJ (1982) Variability in the central equatorial Indian Ocean: I. Ocean dynamics. J Mar Res 40:157–176

    Google Scholar 

  • Miyama T, McCreary JP, Jensen TG, Loschnigg J, Godfrey S, Ishida A (2003) Structure and dynamics of the Indian Ocean cross-equatorial cell. Deep Sea Res Part II 50:2023–2047

    Article  Google Scholar 

  • Miyama T, McCreary JP, Sengupta D, Senan R (2006) Dynamics of quasi-biweekly oscillations in the equatorial Indian Ocean. J Phys Oceanogr 36:827–846

    Article  Google Scholar 

  • Murty VSN, Sarma MSS, Suryanarayana A, Sengupta D, Unnikrishnan AS, Fernando V, Almeida A, Khalap S, Sardar A, Somasundar K, Ravichandran M (2006) Indian moorings: deep-sea current meter moorings in eastern equatorial Indian Ocean. CLIVAR Exchanges, No. 11 (4), International CLIVAR Project Office, Southampton, UK, pp 5–8

  • Ogata T, Sasaki H, Murty VSN, Sarma MSS, Masumoto Y (2008) Intraseasonal meridional current variability in the eastern equatorial Indian Ocean. J Geophys Res 113:C07037. doi:10.1029/2007/JC004331

    Article  Google Scholar 

  • Qu T, Meyers G (2005) Seasonal variation of barrier layer in the southeastern tropical Indian Ocean. J Geophys Res. doi:10.1029/2004JC002816

    Google Scholar 

  • Rao RR, Girish Kumar MS, Ravichandran M, Satheesh Kumar S (2009) Atlas of the tropical Indian Ocean from satellite observations, volume I: sea surface wind vectors and wind stress curl, Indian National Centre for Ocean Information Services (INCOIS), Hyderabad, India. ISBN: 978-81-8424-326-0

  • Rao RR, Horii T, Masumoto Y, Mizuno K (2015) Observed variability in the upper layers at the Equator, 90°E in the Indian Ocean during 2001–2008, 1: zonal currents. Clim Dyn

  • Reppin J, Schott F, Fischer J, Quadfasel D (1999) Equatorial currents and transports in the upper central Indian Ocean. J Geophys Res 104:15495–15514

    Article  Google Scholar 

  • Reverdin G, Luyten J (1986) Near-surface meanders in the equatorial Indian Ocean. J Phys Oceanogr 16:1088–1100

    Article  Google Scholar 

  • Schott F, McCreary JP (2001) The monsoon circulation of the Indian Ocean. Prog Oceanogr 51:1–123

    Article  Google Scholar 

  • Schott F, Reppin J, Fischer J, Quadfasel D (1994) Currents and transports of the monsoon current south of Sri Lanka. J Geophys Res 99:25127–25141

    Article  Google Scholar 

  • Schott FA, McCreary JP, Johnson GC (2004) Shallow over-turning circulations of the tropical-subtropical oceans. In: Wang C, Xie SP, Carton JA (eds) Earth’s climate: the ocean–atmosphere interaction, geophysical monograph series, vol 147. AGU, Washington, pp 261–304

    Google Scholar 

  • Schott FA, Xie SP, McCreary JP (2009) Indian Ocean circulation and climate variability. Rev Geophys 47:RG1002. doi:10.1029/2007RG000245

    Article  Google Scholar 

  • Sengupta D, Senan R, Goswami BN (2001) Origin of intraseasonal variability of circulation in the tropical central Indian Ocean. Geophys Res Lett 28(7):1267–1270

    Article  Google Scholar 

  • Sengupta D, Senan R, Murty VSN, Fernando V (2004) A quasi-biweekly mode in the equatorial Indian Ocean. J Geophys Res 109:C10003. doi:10.1029/2004JC002329

    Article  Google Scholar 

  • Shikhakolli R, Sharma R, Basu S, Gohil BS, Sarkar A, Prasad KVSR (2013) Evaluation of OSCAR ocean surface current product in the tropical Indian Ocean using in situ data. J Earth Syst Sci 122(1):187–199

    Article  Google Scholar 

  • Sikka DR, Gadgil S (1980) On the maximum cloud zone and the ITCZ over Indian longitudes during the southwest monsoon. Mon Weather Rev 108:1840–1853

    Article  Google Scholar 

  • Thompson B, Gnanaseelan C, Salvekar PS (2006) Variability in the Indian Ocean circulation and salinity and its impact on SST anomalies during dipole events. J Mar Res 64:853–880

    Article  Google Scholar 

  • Tsai PTH, O’Brien JJ, Luther ME (1992) The 26-day oscillation observed in the satellite sea surface temperature measurements in the equatorial western Indian Ocean. J Geophys Res 97:9605–9618

    Article  Google Scholar 

  • Waliser DE, Murtugudde R, Lukas L (2004) Indo-Pacific Ocean response to atmospheric intraseasonal variability. Part II: boreal summer and the intraseasonal oscillation. J Geophys Res 109:C03030. doi:10.1029/2003JC002002

    Article  Google Scholar 

  • Wentz FJ, Ashcroft PD, Gentemann CL (2001) Post-launch calibration of the TRMM microwave imager. IEEE Trans Geosci Remote Sens 39(2):415–422

    Article  Google Scholar 

  • Wunsch C, Gill AE (1976) Observations of equatorially trapped waves in Pacific sea level variations. Deep Sea Res 23:371–390

    Google Scholar 

  • Wyrtki K (1973) An equatorial jet in the Indian Ocean. Science 181:262–264

    Article  Google Scholar 

  • Yasunari T (1981) Structure of an Indian summer monsoon system with around 40 day period. J Meteorol Soc Jpn 59:336–354

    Article  Google Scholar 

Download references

Acknowledgments

Highest appreciation is placed on record for the excellent compilation by several persons and organizations of all the data sets utilized in this study. JAMSTEC is responsible for the deployment of ADCP and TRITON CTD moorings in the eastern EIO. The Graphics were generated with GrADS. The encouragement and the facilities provided by the Director General, JAMSTEC are gratefully appreciated. This research was carried out while the first author held a Visiting Senior Scientist position at JAMSTEC with the support of JEPP (Japan Earth Observation Promotion Program) of MEXT (Ministry of Education, Culture, Sports, Science and Technology), Japan.

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Authors and Affiliations

  1. IITM, Pune, India

    R. R. Rao

  2. JAMSTEC, Yokosuka, Japan

    T. Horii, Y. Masumoto & K. Mizuno

  3. University of Tokyo, Tokyo, Japan

    Y. Masumoto

Authors
  1. R. R. Rao
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  2. T. Horii
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  3. Y. Masumoto
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  4. K. Mizuno
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Correspondence to R. R. Rao.

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This paper is a contribution to the special issue on Ocean estimation from an ensemble of global ocean reanalyses, consisting of papers from the Ocean Reanalyses Intercomparsion Project (ORAIP), coordinated by CLIVAR-GSOP and GODAE OceanView. The special issue also contains specific studies using single reanalysis systems.

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Rao, R.R., Horii, T., Masumoto, Y. et al. Observed variability in the upper layers at the Equator, 90°E in the Indian Ocean during 2001–2008, 2: meridional currents. Clim Dyn 49, 1031–1048 (2017). https://doi.org/10.1007/s00382-016-2979-9

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  • DOI: https://doi.org/10.1007/s00382-016-2979-9

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