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Mixing‐length controls on high‐resolution simulations of convective storms
Author(s) -
Hanley Kirsty E.,
Plant Robert S.,
Stein Thorwald H. M.,
Hogan Robin J.,
Nicol John C.,
Lean Humphrey W.,
Halliwell Carol,
Clark Peter A.
Publication year - 2014
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.2356
Subject(s) - storm , mixing (physics) , meteorology , convection , environmental science , convective storm detection , range (aeronautics) , turbulence , grid , atmospheric sciences , geology , mechanics , physics , materials science , geodesy , quantum mechanics , composite material
We perform simulations of several convective events over the southern UK with the Met Office Unified Model (UM) at horizontal grid lengths ranging from 1.5 km to 200 m. Comparing the simulated storms on these days with the Met Office rainfall radar network allows us to apply a statistical approach to evaluate the properties and evolution of the simulated storms over a range of conditions. Here we present results comparing the storm morphology in the model and reality which show that the simulated storms become smaller as grid length decreases and that the grid length that fits the observations best changes with the size of the observed cells. We investigate the sensitivity of storm morphology in the model to the mixing length used in the subgrid turbulence scheme. As the subgrid mixing length is decreased, the number of small storms with high area‐averaged rain rates increases. We show that, by changing the mixing length, we can produce a lower‐resolution simulation which produces similar morphologies to a higher‐resolution simulation.