Open AccessSeamless Stratocumulus Simulation across the Turbulent Gray Zone
Author(s) -
Ian Boutle,
Jack Reeves Eyre,
Adrian Lock
Publication year - 2014
Publication title -
monthly weather review
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.862
H-Index - 179
eISSN - 1520-0493
pISSN - 0027-0644
DOI - 10.1175/mwr-d-13-00229.1
Subject(s) - turbulence , grid , large eddy simulation , meteorology , marine stratocumulus , boundary layer , range (aeronautics) , environmental science , scale (ratio) , numerical weather prediction , mechanics , geology , physics , aerospace engineering , geodesy , aerosol , engineering , quantum mechanics
A pragmatic approach for representing partially resolved turbulence in numerical weather prediction models is introduced and tested. The method blends a conventional boundary layer parameterization, suitable for large grid lengths, with a subgrid turbulence scheme suitable for large-eddy simulation. The key parameter for blending the schemes is the ratio of grid length to boundary layer depth. The new parameterization is combined with a scale-aware microphysical parameterization and tested on a case study forecast of stratocumulus evolution. Simulations at a range of model grid lengths between 1 km and 100 m are compared to aircraft observations. The improved microphysical representation removes the correlation between precipitation rate and model grid length, while the new turbulence parameterization improves the transition from unresolved to resolved turbulence as grid length is reduced.