• Anderson, S. P., R. A. Weller, and R. B. Lukas, 1996: Surface buoyancy forcing and the mixed layer of the western Pacific warm pool: Observations and 1D model results. J. Climate, 9 , 30563085.

    • Search Google Scholar
    • Export Citation
  • Behringer, D., and Y. Xue, 2004: Evaluation of the global ocean data assimilation system at NCEP: The Pacific Ocean. Proc. Eighth Symp. on Integrated Observing and Assimilation Systems for Atmosphere, Oceans, and Land Surface, Seattle, WA, Amer. Meteor. Soc., 2.3. [Available online at http://ams.confex.com/ams/pdfpapers/70720.pdf.].

    • Search Google Scholar
    • Export Citation
  • Bruce, J. G., D. R. Johnson, and J. C. Kindle, 1994: Evidence for eddy formation in the eastern Arabian Sea during the northeast monsoon. J. Geophys. Res., 99 , 76517664.

    • Search Google Scholar
    • Export Citation
  • Bruce, J. G., J. C. Kindle, L. H. Kantha, J. L. Kerling, and J. F. Bailey, 1998: Recent observations and modeling in the Arabian Sea Laccadive High region. J. Geophys. Res., 103 , 75937600.

    • Search Google Scholar
    • Export Citation
  • Colborn, J. G., 1975: Thermal Structure of the Indian Ocean. International Indian Ocean Expedition Oceanogr. Monogr., No. 2, University Press of Hawaii, 173 pp.

    • Search Google Scholar
    • Export Citation
  • Conkright, M. E., R. A. Locarnini, H. E. Garcia, T. D. O’Brien, T. P. Boyer, C. Stephens, and J. J. Antonov, 2002: World Ocean Atlas 2001: Objective Analysis, Data Statistics, and Figures. CD-ROM documentation, National Oceanographic Data Center, 17 pp.

    • Search Google Scholar
    • Export Citation
  • Cutler, A. N., and J. C. Swallow, 1984: Surface currents of the Indian Ocean (to 25°S, 100°E). Met Office Institute of Oceanographic Sciences Rep. 187, 42 pp.

    • Search Google Scholar
    • Export Citation
  • Durand, F., S. R. Shetye, J. Vialard, D. Shankar, S. S. C. Shenoi, C. Ethe, and G. Madec, 2004: Impact of temperature inversions on SST evolution in the South-Eastern Arabian Sea during the pre-summer monsoon season. Geophys. Res. Lett., 31 , L01305. doi:10.1029/2003GL018906.

    • Search Google Scholar
    • Export Citation
  • Gopalakrishna, V. V., Z. Johnson, G. Salgaonkar, K. Nisha, C. K. Rajan, and R. R. Rao, 2005: Observed variability of sea surface salinity and thermal inversions in the Lakshadweep Sea during contrast monsoons. Geophys. Res. Lett., 32 , L18605. doi:10.1029/2005GL023280.

    • Search Google Scholar
    • Export Citation
  • Gopalakrishna, V. V., and Coauthors, 2008: Observed anomalous upwelling in the Lakshadweep Sea during the summer monsoon season of 2005. J. Geophys. Res., 113 , C05001. doi:10.1029/2007JC004240.

    • Search Google Scholar
    • Export Citation
  • Hastenrath, S., and P. J. Lamb, 1979: Climatic Atlas of the Indian Ocean. Part II: The Oceanic Heat Budget. Wisconsin University Press, 84 charts, 93 pp.

    • Search Google Scholar
    • Export Citation
  • Johannessen, O. M., G. Subbaraju, and J. Blindheim, 1987: Seasonal variations of the oceanographic conditions off the southwest coast of India during 1971–1975. J. Fiskerdir. Skr. Ser. Havunders., 18 , 247261.

    • Search Google Scholar
    • Export Citation
  • Kurian, J., and P. N. Vinayachandran, 2006: Formation mechanisms of temperature inversions in the southeastern Arabian Sea. Geophys. Res. Lett., 33 , L17611. doi:10.1029/2006GL027280.

    • Search Google Scholar
    • Export Citation
  • Luis, A. J., and H. Kawamura, 2000: Winter wind forcing and sea surface cooling near the South India tip observed using NSCAT and AVHRR. Remote Sens. Environ., 73 , 5564.

    • Search Google Scholar
    • Export Citation
  • Luis, A. J., and H. Kawamura, 2002: A case study of sea surface temperature–cooling dynamics near the Indian tip during May 1997. J. Geophys. Res., 107 , 3171. doi:10.1029/2000JC000778.

    • Search Google Scholar
    • Export Citation
  • Masson, S., P. Delecluse, J-P. Boulanger, and C. Menkes, 2002: A model study of the seasonal variability and formation mechanisms of the barrier layer in the eastern equatorial Indian Ocean. J. Geophys. Res., 107 , 8017. doi:10.1029/2001JC000832.

    • Search Google Scholar
    • Export Citation
  • Masson, S., and Coauthors, 2005: Impact of barrier layer on winter-spring variability of the southeastern Arabian Sea. Geophys. Res. Lett., 32 , L07703. doi:10.1029/2004GL021980.

    • Search Google Scholar
    • Export Citation
  • McCreary Jr., J. P., P. K. Kundu, and R. L. Molinari, 1993: A numerical investigation of the dynamics, thermodynamics and mixed layer processes in the Indian Ocean. Prog. Oceanogr., 31 , 181244.

    • Search Google Scholar
    • Export Citation
  • Prasanna Kumar, S., and Coauthors, 2004: Intrusion of the Bay of Bengal water into the Arabian Sea during winter monsoon and associated chemical and biological response. Geophys. Res. Lett., 31 , L15304. doi:10.1029/2004GL020247.

    • Search Google Scholar
    • Export Citation
  • Rao, R. R., and R. Sivakumar, 1999: On the possible mechanisms of the evolution of a mini-warm pool during the pre-summer monsoon season and the onset vortex in the southeastern Arabian Sea. Quart. J. Roy. Meteor. Soc., 125 , 787809.

    • Search Google Scholar
    • Export Citation
  • Rao, R. R., and R. Sivakumar, 2003: Seasonal variability of sea surface salinity and salt budget of the mixed layer of the north Indian Ocean. J. Geophys. Res., 108 , 3009. doi:10.1029/2001JC000907.

    • Search Google Scholar
    • Export Citation
  • Shankar, D., and S. R. Shetye, 1997: On the dynamics of the Lakshadweep high and low in the southeastern Arabian Sea. J. Geophys. Res., 102 , 1255112562.

    • Search Google Scholar
    • Export Citation
  • Shankar, D., P. N. Vinayachandran, and A. S. Unnikrishnan, 2002: The monsoon currents in the north Indian Ocean. Prog. Oceanogr., 52 , 63120.

    • Search Google Scholar
    • Export Citation
  • Shankar, D., and Coauthors, 2004: Observational evidence for westward propagation of temperature inversions in the southeastern Arabian Sea. Geophys. Res. Lett., 31 , L08305. doi:10.1029/2004GL019652.

    • Search Google Scholar
    • Export Citation
  • Shenoi, S. S. C., D. Shankar, and S. R. Shetye, 1999: On the sea surface temperature high in the Lakshadweep Sea before the onset of the southwest monsoon. J. Geophys. Res., 104 , 1570315712.

    • Search Google Scholar
    • Export Citation
  • Shetye, S. R., A. D. Gouveia, S. S. C. Shenoi, G. S. Michael, D. Sundar, A. M. Almeida, and K. Santanam, 1991: The coastal currents off western India during the northeast monsoon. Deep-Sea Res., 38A , 15171529.

    • Search Google Scholar
    • Export Citation
  • Shetye, S. R., A. D. Gouveia, D. Shankar, S. S. C. Shenoi, P. N. Vinayachandran, D. Sundar, G. S. Michael, and G. Nampoothiri, 1996: Hydrography and circulation in the western Bay of Bengal during northeast monsoon. J. Geophys. Res., 101 , 1401114025.

    • Search Google Scholar
    • Export Citation
  • Sprintall, J., and M. Tomczak, 1992: Evidence of the barrier layer in the surface layer of the tropics. J. Geophys. Res., 97 , 73057316.

    • Search Google Scholar
    • Export Citation
  • Thadathil, P., and A. K. Gosh, 1992: Surface layer temperature inversion in the Arabian Sea during winter. J. Oceanogr., 48 , 293304.

  • Vinayachandran, P. N., S. Iizuka, and T. Yamagata, 2002: Indian Ocean dipole mode events in an ocean general circulation model. Deep-Sea Res. II, 49 , 15731596.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 114 46 2
PDF Downloads 70 29 2

Reduced Near-Surface Thermal Inversions in 2005–06 in the Southeastern Arabian Sea (Lakshadweep Sea)

View More View Less
  • + National Institute of Oceanography, Dona Paula, Goa, India
  • | # Indian Institute of Tropical Meteorology, Pashan, Pune, India
  • | @ Naval Physical and Oceanographic Laboratory, Kochi, India
  • | 4 Indian National Center for Ocean Information Services, Hyderabad, India
  • | * *Space Application Centre, Ahmedabad, India
  • | ++ Cochin University of Science and Technology, Kochi, India
Restricted access

Abstract

Repeat XBT transects made at near-fortnightly intervals in the Lakshadweep Sea (southeastern Arabian Sea) and ocean data assimilation products are examined to describe the year-to-year variability in the observed near-surface thermal inversions during the winter seasons of 2002–06. Despite the existence of a large low-salinity water intrusion into the Lakshadweep Sea, there was an unusually lower number of near-surface thermal inversions during the winter 2005/06 compared to the other winters. The possible causative mechanisms are examined. During the summer monsoon of 2005 and the following winter season, unusually heavy rainfall occurred over the southwestern Bay of Bengal and the Lakshadweep Sea compared to other years in the study. Furthermore, during the winter of 2005, both the East India Coastal Current and the Winter Monsoon Current were stronger compared to the other years, transporting larger quantities of low salinity waters from the Bay of Bengal into the Lakshadweep Sea where a relatively cooler near-surface thermal regime persisted owing to prolonged upwelling until November 2005. In addition, the observed local surface wind field was relatively stronger, and the net surface heat gain to the ocean was weaker over the Lakshadweep Sea during the postmonsoon season of 2005. Thus, in winter 2005/06, the combination of prolonged upwelling and stronger surface wind field resulting in anomalous net surface heat loss caused weaker secondary warming of the near-surface waters in the Lakshadweep Sea. This led to a weaker horizontal sea surface temperature (SST) gradient between the Lakshadweep Sea and the intruding Bay of Bengal waters and, hence, a reduced number of thermal inversions compared to other winters despite the presence of stronger vertical haline stratification.

Corresponding author address: Ms. K. Nisha, Physical Oceanography Division, National Institute of Oceanography, Dona Paula, Goa-403004, India. Email: knisha@nio.org

Abstract

Repeat XBT transects made at near-fortnightly intervals in the Lakshadweep Sea (southeastern Arabian Sea) and ocean data assimilation products are examined to describe the year-to-year variability in the observed near-surface thermal inversions during the winter seasons of 2002–06. Despite the existence of a large low-salinity water intrusion into the Lakshadweep Sea, there was an unusually lower number of near-surface thermal inversions during the winter 2005/06 compared to the other winters. The possible causative mechanisms are examined. During the summer monsoon of 2005 and the following winter season, unusually heavy rainfall occurred over the southwestern Bay of Bengal and the Lakshadweep Sea compared to other years in the study. Furthermore, during the winter of 2005, both the East India Coastal Current and the Winter Monsoon Current were stronger compared to the other years, transporting larger quantities of low salinity waters from the Bay of Bengal into the Lakshadweep Sea where a relatively cooler near-surface thermal regime persisted owing to prolonged upwelling until November 2005. In addition, the observed local surface wind field was relatively stronger, and the net surface heat gain to the ocean was weaker over the Lakshadweep Sea during the postmonsoon season of 2005. Thus, in winter 2005/06, the combination of prolonged upwelling and stronger surface wind field resulting in anomalous net surface heat loss caused weaker secondary warming of the near-surface waters in the Lakshadweep Sea. This led to a weaker horizontal sea surface temperature (SST) gradient between the Lakshadweep Sea and the intruding Bay of Bengal waters and, hence, a reduced number of thermal inversions compared to other winters despite the presence of stronger vertical haline stratification.

Corresponding author address: Ms. K. Nisha, Physical Oceanography Division, National Institute of Oceanography, Dona Paula, Goa-403004, India. Email: knisha@nio.org

Save