Simulation of monsoon intraseasonal oscillations in a coarse-resolution aquaplanet GCM

Ajaya Ravindran, Boualem Khouider, Andrew Majda

Research output: Contribution to journalArticle

Abstract

The skill of the global climate models (GCMs) to realistically simulate the monsoon intraseasonal oscillations (MISOs) is related to the sensitivity of their convective parameterization schemes. Here we show that by coupling a simple multicloud parameterization to a coarse-resolution aquaplanet GCM, realistic MISOs can be simulated. We conduct three different simulations with a fixed nonhomogeneous sea surface temperature mimicking the Indian Ocean/western Pacific warm pool (WP) centered at the three latitudes 5°N, 10°N, and 15°N, respectively, to replicate the seasonal migration of the Tropical Convergence Zone (TCZ). This results in the generation of mean circulation resembling the monsoonal flow pattern in boreal summer. Succession of eastward propagating Madden-Julian Oscillation (MJO) disturbances with phase speed, amplitude, and structure similar to summer MJOs are simulated when the WP is at 5°N. When the WP is located over 10°N, northward and eastward propagating MISOs are simulated. This case captures the meridional seesaw of convection between continental and oceanic TCZ observed during boreal summer over South Asia. Westward propagating Rossby wave-like disturbances are simulated when the WP is over 15°N congruous with the synoptic disturbances seen over the monsoon trough. The initiation of intraseasonal oscillations in the model can occur internally through organization of convective events above the WP associated with internal dynamics. Key Points Monsoon ISO simulated using multicloud model Three-cloud structure, key for Monsoon ISOs A more realistic parameterization scheme for monsoon ISOs

Original languageEnglish (US)
Pages (from-to)5662-5669
Number of pages8
JournalGeophysical Research Letters
Volume41
Issue number15
DOIs
StatePublished - Aug 16 2014

Fingerprint

intraseasonal variations
monsoons
climate models
global climate
warm pool
climate modeling
monsoon
oscillation
simulation
Madden-Julian Oscillation
parameterization
summer
disturbances
disturbance
Madden-Julian oscillation
Indian Ocean
sea surface temperature
Rossby wave
troughs
planetary waves

Keywords

  • convective parameterization
  • monsoon intraseasonal oscillations
  • tropical convection

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)
  • Geophysics

Cite this

Simulation of monsoon intraseasonal oscillations in a coarse-resolution aquaplanet GCM. / Ravindran, Ajaya; Khouider, Boualem; Majda, Andrew.

In: Geophysical Research Letters, Vol. 41, No. 15, 16.08.2014, p. 5662-5669.

Research output: Contribution to journalArticle

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