The Dynamics of Double Monsoon Onsets

Maria K. Flatau Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California

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Piotr J. Flatau Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California

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Daniel Rudnick Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California

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Abstract

Double monsoon onset develops when the strong convection in the Bay of Bengal is accompanied by the monsoonlike circulation and appears in the Indian Ocean in early May, which is about 3 weeks earlier than the climatological date of the onset (1 Jun). The initial “bogus onset” is followed by the flow weakening or reversal and clear-sky and dry conditions over the monsoon region. The best example of such a phenomenon is the development of the summer monsoon in 1995, when monsoonlike perturbations that appeared in mid-May disappeared by the end of the month and were followed by a heat wave in India, delaying onset of the monsoon. The climatology of double onsets is analyzed, and it is shown that they are associated with delay of the monsoon rainfall over India. This analysis indicates that the development of bogus onsets depends on the timing of intraseasonal oscillation in the Indian Ocean and the propagation of convective episodes into the western Pacific. There is evidence that an SST evolution in the Bay of Bengal and the western Pacific plays an important role in this phenomenon. It is shown that in the case of the double monsoon onset it is possible to predict hot and dry conditions in India before the real monsoon onset. In the 32 yr of climatological data, six cases of double monsoon onset were identified.

Corresponding author address: Dr. Piotr J. Flatau, Scripps Institution of Oceanography and California Space Institute, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0221. Email: pflatau@ucsd.edu

Abstract

Double monsoon onset develops when the strong convection in the Bay of Bengal is accompanied by the monsoonlike circulation and appears in the Indian Ocean in early May, which is about 3 weeks earlier than the climatological date of the onset (1 Jun). The initial “bogus onset” is followed by the flow weakening or reversal and clear-sky and dry conditions over the monsoon region. The best example of such a phenomenon is the development of the summer monsoon in 1995, when monsoonlike perturbations that appeared in mid-May disappeared by the end of the month and were followed by a heat wave in India, delaying onset of the monsoon. The climatology of double onsets is analyzed, and it is shown that they are associated with delay of the monsoon rainfall over India. This analysis indicates that the development of bogus onsets depends on the timing of intraseasonal oscillation in the Indian Ocean and the propagation of convective episodes into the western Pacific. There is evidence that an SST evolution in the Bay of Bengal and the western Pacific plays an important role in this phenomenon. It is shown that in the case of the double monsoon onset it is possible to predict hot and dry conditions in India before the real monsoon onset. In the 32 yr of climatological data, six cases of double monsoon onset were identified.

Corresponding author address: Dr. Piotr J. Flatau, Scripps Institution of Oceanography and California Space Institute, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0221. Email: pflatau@ucsd.edu

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  • Chen, T-C., R-W. Tzeng, and M. Yen, 1988: Development and life cycle of the Indian monsoon: Effect of the 30–50 day oscillation. Mon. Wea. Rev, 116 , 21832199.

    • Search Google Scholar
    • Export Citation
  • De, U. S., D. S. Desai, and S. G. Bhandari, 1996: Weather in India. Mausam, 47 , 205218.

  • Fieux, M., and H. Stommel, 1977: Onset of the southwest monsoon over the Arabian Sea. Mon. Wea. Rev, 105 , 231236.

  • Gill, A. E., 1980: Some simple solutions for heat-induced tropical circulation. Quart. J. Roy. Meteor. Soc, 106 , 447462.

  • Goswami, B. N., V. Krishnamurthy, and H. Annamalai, 1999: A broad-scale circulation index for the interannual variability of the Indian summer monsoon. Quart. J. Roy. Meteor. Soc, 125 , 611633.

    • Search Google Scholar
    • Export Citation
  • Halpert, M. S., G. D. Bell, V. E. Kousky, and C. F. Ropelewski, 1996: Climate assessment for 1995. Bull. Amer. Meteor. Soc, 77 , S. 1S43.

    • Search Google Scholar
    • Export Citation
  • Hsu, H. H., C. T. Terng, and C. T. Chen, 1999: Evolution of large-scale circulation and heating during the first transition of Asian summer monsoon. J. Climate, 12 , 793810.

    • Search Google Scholar
    • Export Citation
  • Joseph, P., J. Eischeid, and R. Pyle, 1994: Interannual variability of the onset of the Indian summer monsoon and its association with atmospheric features, El Niño, and sea surface temperature anomalies. J. Climate, 7 , 81105.

    • Search Google Scholar
    • Export Citation
  • Lau, K-M., H-T. Wu, and S. Yang, 1998: Hydrologic processes associated with the first transition of the Asian summer monsoon. Bull. Amer. Meteor. Soc, 79 , 18711882.

    • Search Google Scholar
    • Export Citation
  • Lau, K-M., K-M. Kim, and S. Yang, 2000: Dynamical and boundary forcing characteristics of regional components of the Asian summer monsoon. J. Climate, 13 , 24612482.

    • Search Google Scholar
    • Export Citation
  • Mukherjee, A. K., and K. P. Padmanabham, 1978: Simultaneous occurrence of tropical cyclones on either side of the equator in the Indian Ocean area. Indian J. Meteor. Hydrol. Geophys, 28 , 211222.

    • Search Google Scholar
    • Export Citation
  • Pearce, R., and U. Mohanty, 1984: Onsets of the Asian summer monsoon 1979–82. J. Atmos. Sci, 41 , 16201639.

  • Reynolds, R. W., and T. M. Smith, 1994: Improved global sea surface temperature analyses. J. Climate, 7 , 929948.

  • Rudnick, D. L., R. Weller, T. Dickey, J. Marra, and C. Langdon, 1997: Moored instruments weather Arabian Sea monsoons, yield data. Eos, Trans. Amer. Geophys. Union, 78 , 120121.

    • Search Google Scholar
    • Export Citation
  • Schott, F., and J. Fernandez-Partagas, 1981: The onset of the summer monsoon during the FGGE 1979 experiment off the East African Coast: A comparison of wind data collected by different means. J. Geophys. Res, 86 , 41734180.

    • Search Google Scholar
    • Export Citation
  • Soman, M., and J. Slingo, 1997: Sensitivity of the Asian summer monsoon to aspects of sea-surface temperature anomalies in the tropical Pacific Ocean. Quart. J. Roy. Meteor. Soc, 123 , 309336.

    • Search Google Scholar
    • Export Citation
  • Wang, B., and H. Rui, 1990: Synoptic climatology of transient tropical intraseasonal convection anomalies: 1975–1985. Meteor. Atmos. Phys, 44 , 4361.

    • Search Google Scholar
    • Export Citation
  • Wang, B., and X. Xie, 1997: A model for the boreal summer intraseasonal oscillation. J. Atmos. Sci, 54 , 7286.

  • Webster, P., 1986: The variable and interactive monsoon. Monsoons, J. S. Fein, and P. L. Stephens, Eds., John Wiley and Sons, 269–330.

    • Search Google Scholar
    • Export Citation
  • Webster, P., and S. Yang, 1992: Monsoon and ENSO: Selectively interactive systems. Quart. J. Roy. Meteor. Soc, 118 , 877926.

  • Webster, P., V. O. Magana, T. N. Palmer, J. Shukla, R. A. Tomas, M. Yanai, and T. Yasunari, 1998: Monsoons: Processes, predictability, and the prospects for prediction. J. Geophys. Res, 103 , 1445114510.

    • Search Google Scholar
    • Export Citation
  • Weller, R., D. Rudnick, and N. Brink, 1995: Meteorological variability and air–sea fluxes at a closely spaced array of surface moorings. J. Geophys. Res, 100 , 48674883.

    • Search Google Scholar
    • Export Citation
  • Weller, R., M. Baumgartner, S. Josey, A. Fischer, and J. Kindle, 1998: Atmospheric forcing in the Arabian Sea during 1994–1995: Observations and comparisons with climatology and models. Deep-Sea Res. II, Topical Stud. Oceanogr, 45 , 19611999.

    • Search Google Scholar
    • Export Citation
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