Realistic initiation and dynamics of the Madden-Julian Oscillation in a coarse resolution aquaplanet GCM

Ajaya Ravindran, Boualem Khouider, Andrew Majda

Research output: Contribution to journalArticle

Abstract

The main mechanisms for the initiation and propagation of the Madden-Julian Oscillation (MJO) are still widely debated. The capacity of operational global climate models (GCMs) to correctly simulate the MJO is hindered by the inadequacy of the underlying cumulus parameterizations. Here we show that a coarse resolution GCM, coupled to a simple multicloud model parameterization mimicking the observed dynamics and physical structure of organized tropical convection, simulates the MJO in an idealized setting of an aquaplanet without ocean dynamics. We impose a fixed nonhomogeneous sea-surface temperature replicating the Indian Ocean/Western Pacific warm pool. This results in a succession of MJOs with realistic phase speed, amplitude, and physical structure. Each MJO event is initiated at a somewhat random location over the warm pool and dies sometimes near the eastern boundary of the warm pool and sometimes at a random location way beyond the warm pool. Also occasionally the MJO events stall at the center of maximum heating. This is reminiscent of the fact that in nature some MJOs stall over the maritime continent while others reach the central Pacific Ocean and beyond. The initiation mechanism in the model is believed to be a combination of persistent intermittent convective events interacting with observed large-scale flow patterns and internal tropical dynamics. The large-scale flow patterns are associated with planetary-scale dry Kelvin waves that are triggered by preceding MJO events and circle the globe, while congestus cloud decks on the flanks of the warm pool are believed to force Rossby gyres which then funnel moisture toward the equatorial region. Key Points Realistic MJO initiation and dynamics in a GCM Used a simple three layer multicloud convection scheme in the simulation A different initiation mechanism for the MJO as opposed to the existing theory

Original languageEnglish (US)
Pages (from-to)6252-6257
Number of pages6
JournalGeophysical Research Letters
Volume40
Issue number23
DOIs
StatePublished - Dec 16 2013

Fingerprint

Madden-Julian Oscillation
Madden-Julian oscillation
climate models
global climate
climate modeling
warm pool
flow pattern
parameterization
convection
flow distribution
gyres
ocean dynamics
Kelvin wave
Kelvin waves
ocean
cumulus
funnels
equatorial regions
globes
Indian Ocean

Keywords

  • GCM
  • MJO

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)
  • Geophysics

Cite this

Realistic initiation and dynamics of the Madden-Julian Oscillation in a coarse resolution aquaplanet GCM. / Ravindran, Ajaya; Khouider, Boualem; Majda, Andrew.

In: Geophysical Research Letters, Vol. 40, No. 23, 16.12.2013, p. 6252-6257.

Research output: Contribution to journalArticle

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