1/f noise and pulse-like events in the tropical atmospheric surface variabilities

Jun Ichi Yano, Richard Blender, Chidong Zhang, Klaus Fraedrich

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


This study discusses the 1/f-noise behaviour and its connection with pulse-like events in tropical surface meteorological data. The 1/f noise, with f being frequency, refers to the unique spectrum shape of signals that represents the same degree of variability for a whole spectrum range with very long lag-correlations. The pulse-like events are characterized by their high localizations in time and a lack of a distinct spectrum peak. Approximate 1/f-noise behaviour is found in tropical surface temperature, moisture, and wind speed for periods of 1 hour to beyond 10 days and in oceanic wind stress up to 2-year periods. The origin of the 1/f noise can be closely tied to pulse-like events with a highly intermittent nature in the time series. Examples for such pulse-like events include the cumulus convection events leading to convective downdraughts and intraseasonal westerly wind events associated with the Madden-Julian oscillations (MJO). A method based on the wavelet is introduced to extract individual pulse-like events. These events are characterized by a 1/f spectrum extending up to 1-2 decades of frequency centred around their characteristic durations. Their successive occurrences are mutually uncorrelated and the individual pulse-like events themselves constitute a 1/f spectrum for a frequency range around their durations. The superposition of these events of various durations yields the 1/f-noise spectrum for much wider ranges. Physical implications of these findings to convective quasi-equilibrium and MJO-El Niño Southern Oscillation relationship are discussed.

Original languageEnglish (US)
Pages (from-to)1697-1721
Number of pages25
JournalQuarterly Journal of the Royal Meteorological Society
Issue number600 PART A
StatePublished - Jul 2004


  • Madden-Julian oscillations
  • Scaling
  • Tropical convection

ASJC Scopus subject areas

  • Atmospheric Science


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