Role of stratiform heating on the organization of convection over the monsoon trough

R. S. Ajayamohan, Boualem Khouider, Andrew J. Majda, Qiang Deng

Research output: Contribution to journalArticle

Abstract

It has been recently demonstrated that stratiform heating plays a critical role in the scale-selection of organized tropical convection, in an aquaplanet version of a coarse-resolution atmospheric general circulation model coupled to a stochastic multicloud cumulus parameterization scheme. It is shown that Madden–Julian oscillation-like organization dominates when the model is tuned to produce strong and long lived stratiform heating while it gives rise to mostly convectively coupled waves in the case of weak and short lived stratiform clouds. The study is extended here to the case of an asymmetric forcing mimicking the migration of the intertropical convergence zone (ITCZ) during summer to understand the impact of changes in stratiform heating on the monsoon dynamics. Consistent with the equatorial ITCZ case, strong and long lived stratiform heating promotes northward and eastward moving intraseasonal disturbances while weak and short lived stratiform heating yields mostly westward propgating synoptic scale low pressure systems. Moreover, the underlying intraseasonal versus low pressure system activity seems to impact the strength and extend of the monsoon trough (MT). In the regime with intraseasonal activity the MT is much stronger and extends northward while in the low pressure system case MT is some what weaker in strength but extends further westward. In the low pressure dominated regime, the background vorticity and zonal wind profiles over the monsoon trough are consistent with the observations.

Original languageEnglish (US)
Pages (from-to)3641-3660
Number of pages20
JournalClimate Dynamics
Volume47
Issue number12
DOIs
StatePublished - Dec 1 2016

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Keywords

  • Low pressure systems
  • Monsoon Intraseasonal oscillations
  • Monsoon trough
  • Northward propagation
  • Organized convection
  • Stochastic parametrization
  • Stratiform heating

ASJC Scopus subject areas

  • Atmospheric Science

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