Multicloud convective parametrizations with crude vertical structure

Boualem Khouider, Andrew J. Majda

Research output: Contribution to journalArticle

Abstract

Recent observational analysis reveals the central role of three multi-cloud types, congestus, stratiform, and deep convective cumulus clouds, in the dynamics of large scale convectively coupled Kelvin waves, westward propagating two-day waves, and the Madden-Julian oscillation. The authors have recently developed a systematic model convective parametrization highlighting the dynamic role of the three cloud types through two baroclinic modes of vertical structure: a deep convective heating mode and a second mode with low level heating and cooling corresponding respectively to congestus and stratiform clouds. The model includes a systematic moisture equation where the lower troposphere moisture increases through detrainment of shallow cumulus clouds, evaporation of stratiform rain, and moisture convergence and decreases through deep convective precipitation and a nonlinear switch which favors either deep or congestus convection depending on whether the troposphere is moist or dry. Here several new facets of these multi-cloud models are discussed including all the relevant time scales in the models and the links with simpler parametrizations involving only a single baroclinic mode in various limiting regimes. One of the new phenomena in the multi-cloud models is the existence of suitable unstable radiative convective equilibria (RCE) involving a larger fraction of congestus clouds and a smaller fraction of deep convective clouds. Novel aspects of the linear and nonlinear stability of such unstable RCE's are studied here. They include new modes of linear instability including mesoscale second baroclinic moist gravity waves, slow moving mesoscale modes resembling squall lines, and large scale standing modes. The nonlinear instability of unstable RCE's to homogeneous perturbations is studied with three different types of nonlinear dynamics occurring which involve adjustment to a steady deep convective RCE, periodic oscillation, and even heteroclinic chaos in suitable parameter regimes.

Original languageEnglish (US)
Pages (from-to)351-375
Number of pages25
JournalTheoretical and Computational Fluid Dynamics
Volume20
Issue number5-6
DOIs
StatePublished - Nov 2006

Fingerprint

Parametrization
Vertical
Moisture
cumulus clouds
moisture
baroclinic mode
Cloud Model
Unstable
cumulus
troposphere
Troposphere
Heating
Madden-Julian Oscillation
Oscillation
Kelvin waves
Nonlinear Instability
heating
stratiform cloud
squall line
Madden-Julian oscillation

Keywords

  • Bifurcation
  • Congestus clouds
  • Convective instability
  • Deep convective clouds
  • Heteroclinic orbits
  • Intermediate convective parametrizations
  • Moist gravity waves
  • Multicloud models
  • Periodic solutions
  • Stratiform clouds
  • Tropical convection

ASJC Scopus subject areas

  • Fluid Flow and Transfer Processes
  • Oceanography
  • Computational Mechanics
  • Mechanics of Materials
  • Applied Mathematics
  • Physics and Astronomy(all)
  • Physics and Astronomy (miscellaneous)
  • Condensed Matter Physics

Cite this

Multicloud convective parametrizations with crude vertical structure. / Khouider, Boualem; Majda, Andrew J.

In: Theoretical and Computational Fluid Dynamics, Vol. 20, No. 5-6, 11.2006, p. 351-375.

Research output: Contribution to journalArticle

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