The Three-Dimensional Morphology of Simulated and Observed Convective Storms over Southern England

A set of high-resolution radar observations of convective storms has been collected to evaluate such storms in the Met Office Unified Model during the Dynamical and Microphysical Evolution of Convective Storms (DYMECS) project. The 3-GHz Chilbolton Advanced Meteorological Radar was set up with a sca...

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Bibliographic Details
Published in:Monthly weather review 2014-09, Vol.142 (9), p.3264-3283
Main Authors: Stein, Thorwald H M, Hogan, Robin J, Hanley, Kirsty E, Nicol, John C, Lean, Humphrey W, Plant, Robert S, Clark, Peter A, Halliwell, Carol E
Format: Article
Language:English
Subjects:
Algorithms
Convection
Convective storms
Crystals
Drizzle
Graupel
Heavy rainfall
Ice
Ice crystals
Meteorological radar
Meteorology
Modelling
Morphology
Precipitation
Radar
Radar networks
Rain
Rainfall
Simulation
Storms
Structures
Synoptic conditions
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Summary:A set of high-resolution radar observations of convective storms has been collected to evaluate such storms in the Met Office Unified Model during the Dynamical and Microphysical Evolution of Convective Storms (DYMECS) project. The 3-GHz Chilbolton Advanced Meteorological Radar was set up with a scan-scheduling algorithm to automatically track convective storms identified in real time from the operational rainfall radar network. More than 1000 storm observations gathered over 15 days in 2011 and 2012 are used to evaluate the model under various synoptic conditions supporting convection. In terms of the detailed three-dimensional morphology, storms in the 1500-m grid length simulations are shown to produce horizontal structures a factor of 1.5–2 wider compared to radar observations. A set of nested model runs at grid lengths down to 100 m show that the models converge in terms of storm width, but the storm structures in the simulations with the smallest grid lengths are too narrow and too intense compared to the radar observations. The modeled storms were surrounded by a region of drizzle without ice reflectivities above 0 dB Z aloft, which was related to the dominance of ice crystals and was improved by allowing only aggregates as an ice particle habit. Simulations with graupel outperformed the standard configuration for heavy-rain profiles, but the storm structures were a factor of 2 too wide and the convective cores 2 km too deep.
ISSN:0027-0644
1520-0493
DOI:10.1175/MWR-D-13-00372.1