Publication Abstracts

Stevens et al. 2005

Stevens, B., C.-H. Moeng, A.S. Ackerman, C.S. Bretherton, A. Chlond, S. de Roode, J. Edwards, J.-C. Golaz, H. Jiang, M. Khairoutdinov, M.P. Kirkpatrick, D.C. Lewellen, A. Lock, F. Müller, D.E. Stevens, E. Whelan, and P. Zhu, 2005: Evaluation of large-eddy simulations via observations of nocturnal marine stratocumulus. Mon. Weather Rev., 133, 1443-1462, doi:10.1175/MWR2930.1.

Data from the first research flight (RF01) of the second Dynamics and Chemistry of Marine Stratocumulus (DYCOMS-II) field study are used to evaluate the fidelity with which large-eddy simulations (LESs) can represent the turbulent structure of stratocumulus-topped boundary layers. The initial data and forcings for this case placed it in an interesting part of parameter space, near the boundary where cloud-top mixing is thought to render the cloud layer unstable on the one hand, or tending toward a decoupled structure on the other hand. The basis of this evaluation consists of sixteen 4-h simulations from 10 modeling centers over grids whose vertical spacing was 5 m at the cloud-top interface and whose horizontal spacing was 35 m. Extensive sensitivity studies of both the configuration of the case and the numerical setup also enhanced the analysis. Overall it was found that (i) if efforts are made to reduce spurious mixing at cloud top, either by refining the vertical grid or limiting the effects of the subgrid model in this region, then the observed turbulent and thermodynamic structure of the layer can be reproduced with some fidelity; (ii) the base, or native configuration of most simulations greatly overestimated mixing at cloud top, tending toward a decoupled layer in which cloud liquid water path and turbulent intensities were grossly underestimated; (iii) the sensitivity of the simulations to the representation of mixing at cloud top is, to a certain extent, amplified by particulars of this case. Overall the results suggest that the use of LESs to map out the behavior of the stratocumulus-topped boundary layer in this interesting region of parameter space requires a more compelling representation of processes at cloud top. In the absence of significant leaps in the understanding of subgrid-scale (SGS) physics, such a representation can only be achieved by a significant refinement in resolution — a refinement that, while conceivable given existing resources, is probably still beyond the reach of most centers.

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BibTeX Citation

  author={Stevens, B. and Moeng, C.-H. and Ackerman, A. S. and Bretherton, C. S. and Chlond, A. and de Roode, S. and Edwards, J. and Golaz, J.-C. and Jiang, H. and Khairoutdinov, M. and Kirkpatrick, M. P. and Lewellen, D. C. and Lock, A. and Müller, F. and Stevens, D. E. and Whelan, E. and Zhu, P.},
  title={Evaluation of large-eddy simulations via observations of nocturnal marine stratocumulus},
  journal={Mon. Weather Rev.},

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RIS Citation

ID  - st01310g
AU  - Stevens, B.
AU  - Moeng, C.-H.
AU  - Ackerman, A. S.
AU  - Bretherton, C. S.
AU  - Chlond, A.
AU  - de Roode, S.
AU  - Edwards, J.
AU  - Golaz, J.-C.
AU  - Jiang, H.
AU  - Khairoutdinov, M.
AU  - Kirkpatrick, M. P.
AU  - Lewellen, D. C.
AU  - Lock, A.
AU  - Müller, F.
AU  - Stevens, D. E.
AU  - Whelan, E.
AU  - Zhu, P.
PY  - 2005
TI  - Evaluation of large-eddy simulations via observations of nocturnal marine stratocumulus
JA  - Mon. Weather Rev.
VL  - 133
SP  - 1443
EP  - 1462
DO  - 10.1175/MWR2930.1
ER  -

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