• A note on new indices for the equatorial Indian Ocean oscillation

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    • Keywords

       

      Indian summer monsoon variability; equatorial Indian Ocean oscillation; Indian Ocean dipole; El Ni˜ño and southern oscillation.

    • Abstract

       

      It is now well known that there is a strong association of the extremes of the Indian summer monsoon rainfall (ISMR) with the El Ni˜no and southern oscillation (ENSO) and the Equatorial Indian Ocean Oscillation (EQUINOO), later being an east–west oscillation in convection anomaly over the equatorial Indian Ocean. So far, the index used for EQUINOO is EQWIN, which is based on the surface zonal wind over the central equatorial Indian Ocean. Since the most important attribute of EQUINOO is the oscillation in convection/precipitation, we believe that the indices based on convection or precipitation would be more appropriate. Continuous and reliable data on outgoing longwave radiation (OLR), and satellite derived precipitation are now available from 1979 onwards. Hence, in this paper, we introduce new indices for EQUINOO, based on the difference in the anomaly of OLR/precipitation between eastern and western parts of the equatorial Indian Ocean. We show that the strong association of extremes of the Indian summer monsoon with ENSO and EQUINOO is also seen when the new indices are used to represent EQUINOO.

    • Author Affiliations

       

      P A Francis1 Sulochana Gadgil2

      1. Indian National Centre for Ocean Information Services, Ministry of Earth Sciences, Hyderabad 500 090, India.
      2. Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore 560 012, India.
    • Dates

       
  • Journal of Earth System Science | News

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