The scale dependence and structure of convergence fields preceding the initiation of deep convection

Birch, Cathryn E.; Marsham, John H.; Parker, Douglas J.; Taylor, Christopher M.. 2014 The scale dependence and structure of convergence fields preceding the initiation of deep convection. Geophysical Research Letters, 41 (13). 4769-4776.

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Links between convergence and convection are poor in global models, and poor representation of convection is the source of many model biases in the tropics. State-of-the-art convection-permitting simulations allow us to analyze realistic convection statistically. The analysis of fractal dimension is used to show that in convection-permitting simulations (grid spacings 1.5, 4, and 12 km) of the West African monsoon, 50% of deep convective initiations occur in the near vicinity of low-level boundary layer convergence lines that are orientated along the mean wind. In these simulations, more than 80% of the initiations occur within large-scale (300 × 300 km) convergence, with some 20% in large-scale divergence, and almost all cases occur within local scale (60 × 60 km) convergence. The behavior alters in a simulation with a convection scheme and a grid spacing of 12 km; initiation is less frequent over convergence lines, and there is less dependency on high-magnitude low-level local convergence.

Item Type: Publication - Article
Digital Object Identifier (DOI):
UKCEH and CEH Sections/Science Areas: Reynard
ISSN: 0094-8276
Additional Keywords: convection, low-level convergence, Met Office Unified Model, triggering, convection permitting, parameterization
NORA Subject Terms: Meteorology and Climatology
Date made live: 31 Jul 2014 11:55 +0 (UTC)

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