Some aspects of the 30–50 day oscillation

  • S. V. Kasture
  • R. N. Keshavamurty


The structure and interannual variability of the 30–50 day oscillation over the Indian region have been studied during the monsoon season. The power spectra of the zonal component of wind show large power in the 30–50 day time scale. The oscillation has a meridional wavelength of about 25° latitude and a slow northward phase speed of about 0.7° latitude per day. The oscillation also has some interannual variability. The periods are somewhat longer during the drought years.


Oscillation subseasonal oscillation active break monsoon cycle interannual variability 


  1. Alexander G, Keshavamurty R N, De U S, Chellapa R, Das S K and Pillai P V 1978 Fluctuations of monsoon activity;Indian J. Meteorol. Hydrol. Geophys. 29 76–87Google Scholar
  2. Dakshinamurti J and Keshavamurty R N 1978 On oscillation of period around one month in the Indian summer monsoon;Indian J. Meteorol. Hydrol. Geophys. 27 201–208Google Scholar
  3. Keshavamurty R N 1973On the maintenance of the mean Indian southwest monsoon circulation and the structure and energetics of monsoon disturbances; Ph.D. thesis, Mysore University, IndiaGoogle Scholar
  4. Krishnamurti T N, Jayakumar P K, Sheng J, Surgi N and Kumar A 1985 Divergent circulations on the 30–50 day time scale;J. Atmos. Sci. 42 364–375CrossRefGoogle Scholar
  5. Krishnamurti T N and Subramanyam D 1982 The 30–50 day mode at 850 mb during MONEX;J. Atmos. Sci. 39 2088–2095CrossRefGoogle Scholar
  6. Lorenc A C 1984 The evolution of planetary scale 200 mb divergent flow during the FGGE year;Q.J.R. Meteorol. Soc. 110 427–441CrossRefGoogle Scholar
  7. Murakami T, Nakawa and He J H 1983 40–50 day oscillations during the 1979 northern hemispheric summer; Tech. Rep. No. UHMET 83-02. Department of Meteorology, University of Hawaii, Honolulu, HawaiiGoogle Scholar
  8. W M O Tech. Note No. 79 (1966)Google Scholar
  9. Yasumari T 1979 Cloudiness fluctuations associated with the northern hemisphere summer monsoon over India;J. Meteorol. Soc. Jpn. 58 225–229Google Scholar

Copyright information

© Indian Academy of Sciences 1987

Authors and Affiliations

  • S. V. Kasture
    • 1
  • R. N. Keshavamurty
    • 1
  1. 1.Physical Research LaboratoryNavrangpura, AhmedabadIndia

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