Low and high frequency Madden-Julian oscillations in austral summer: Interannual variations

Takeshi Izumo, Sébastien Masson, Jérome Vialard, Clément de Boyer Montegut, Swadhin K. Behera, Gurvan Madec, Keiko Takahashi, Toshio Yamagata

Research output: Contribution to journalArticlepeer-review

33 Citations (Scopus)

Abstract

The Madden-Julian oscillation (MJO) is the main component of intraseasonal variability of the tropical convection, with clear climatic impacts at an almost-global scale. Based on satellite observations, it is shown that there are two types of austral-summer MJO events (broadly defined as 30-120 days convective variability with eastward propagation of about 5 m/s). Equatorial MJO events have a period of 30-50 days and tend to be symmetric about the equator, whereas MJO events centered near 8°S tend to have a longer period of 55-100 days. The lowerfrequency variability is associated with a strong upperocean response, having a clear signature in both sea surface temperature and its diurnal cycle. These two MJO types have different interannual variations, and are modulated by the Indian Ocean Dipole (IOD). Following a negative IOD event, the lower-frequency southern MJO variability increases, while the higher-frequency equatorial MJO strongly diminishes. We propose two possible explanations for this change in properties of the MJO. One possibility is that changes in the background atmospheric circulation after an IOD favour the development of the low-frequency MJO. The other possibility is that the shallower thermocline ridge and mixed layer depth, by enhancing SST intraseasonal variability and thus ocean-atmosphere coupling in the southwest Indian Ocean (the breeding ground of southern MJO onset), favour the lower-frequency southern MJO variability.

Original languageEnglish
Pages (from-to)669-683
Number of pages15
JournalClimate Dynamics
Volume35
Issue number4
DOIs
Publication statusPublished - 2010
Externally publishedYes

Keywords

  • Air-sea interactions
  • Australian weather
  • Diurnal cycle
  • El Nino southern oscillation (ENSO)
  • Indian Ocean dipole (IOD)
  • Interannual variations
  • Intraseasonal Madden-Julian oscillation (MJO)
  • Mixed layer
  • Ocean-atmosphere coupling
  • Oceanic diurnal warm layers
  • Seychelles-Chagos thermocline ridge/thermocline dome of the Indian Ocean

ASJC Scopus subject areas

  • Atmospheric Science

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