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The impact of deformation strain on the formation of banded clouds in idealized modeling experiments

Gray, S. L. ORCID: and Dacre, H. F. ORCID: (2008) The impact of deformation strain on the formation of banded clouds in idealized modeling experiments. Quarterly Journal of the Royal Meteorological Society, 134 (633). pp. 859-874. ISSN 1477-870X

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To link to this item DOI: 10.1002/qj.262


Experiments are performed using an idealized version of an operational forecast model to determine the impact on banded frontal clouds of the strength of deformational forcing, low-level baroclinicity, and model representation of convection. Line convection is initiated along the front, and slantwise bands extend from the top of the line-convection elements into the cold air. This banding is attributed primarily to M adjustment. The cross-frontal spreading of the cold pool generated by the line convection leads to further triggering of upright convection in the cold air that feeds into these slantwise bands. Secondary low-level bands form later in the simulations; these are attributed to the release of conditional symmetric instability. Enhanced deformation strain leads to earlier onset of convection and more coherent line convection. A stronger cold pool is generated, but its speed is reduced relative to that seen in experiments with weaker deformational strain, because of inhibition by the strain field. Enhanced low-level baroclinicity leads to the generation of more inertial instability by line convection (for a given capping height of convection), and consequently greater strength of the slantwise circulations formed by M adjustment. These conclusions are based on experiments without a convective-parametrization scheme. Experiments using the standard or a modified scheme for this model demonstrate known problems with the use of this scheme at the awkward 4 km grid length used in these simulations. Copyright © 2008 Royal Meteorological Society

Item Type:Article
Divisions:Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:1245
Uncontrolled Keywords:conditional symmetric instability (CSI) •delta M adjustment • slantwise circulations
Publisher:Royal Meteorological Society

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