TY - JOUR

T1 - An Investigation of the Grid Sensitivity in Large-Eddy Simulations of the Stable Boundary Layer

AU - Maronga, Björn

AU - Li, Dan

N1 - Funding Information: We would like to thank the two anonymous reviewers for many helpful suggestions to improve the paper. Furthermore, we are grateful to Yi Dai, Sukanta Basu, and Stephan de Roode (all at Delft University of Technology, the Netherlands) and particularly Siegfried Raasch (Leibniz University Hannover) for discussions on the topic. DL acknowledges support from the U.S. National Science Foundation under Grant AGS-1853354 and the Alexander von Humboldt Foundation which supported his visit to Leibniz University Hannover. Simulations were carried out on the computer clusters of the North-German Supercomputing Alliance (HLRN).

PY - 2022/2

Y1 - 2022/2

N2 - We revisit the longstanding problem of grid sensitivity, i.e., the lack of grid convergence in large-eddy simulations (LES) of the stable boundary layer. We use a comprehensive set of LES of the well-known Global Energy and Water Cycle Experiment Atmospheric Boundary Layer Study 1 (GABLS1) case with varying grid spacings between 12.5 m and 1 m to investigate several physical processes and numerical features that are possible causes of grid sensitivity. Our results demonstrate that there are two resolution regimes in which grid sensitivity manifests differently. We find that changing the numerical advection schemes and the subgrid-scale models alters the simulation results, but the options tested do not fully address the grid-sensitivity issue. Moreover, sensitivity runs suggest that the surface boundary condition and the interaction of the surface with the near-surface flow, as well as the mixing with the free atmosphere, are unlikely to be the causes of the observed grid sensitivity. One interesting finding is that the grid sensitivity in the fine grid-spacing regime (grid spacings ≤2m) is closely related to the reduction in the energy content of large-scale turbulence, leading to less turbulence kinetic energy and hence lower boundary-layer heights. The present work demonstrates that there is still an urgent need to address this grid-sensitivity issue in order to perform reliable LES of the stable boundary layer.

AB - We revisit the longstanding problem of grid sensitivity, i.e., the lack of grid convergence in large-eddy simulations (LES) of the stable boundary layer. We use a comprehensive set of LES of the well-known Global Energy and Water Cycle Experiment Atmospheric Boundary Layer Study 1 (GABLS1) case with varying grid spacings between 12.5 m and 1 m to investigate several physical processes and numerical features that are possible causes of grid sensitivity. Our results demonstrate that there are two resolution regimes in which grid sensitivity manifests differently. We find that changing the numerical advection schemes and the subgrid-scale models alters the simulation results, but the options tested do not fully address the grid-sensitivity issue. Moreover, sensitivity runs suggest that the surface boundary condition and the interaction of the surface with the near-surface flow, as well as the mixing with the free atmosphere, are unlikely to be the causes of the observed grid sensitivity. One interesting finding is that the grid sensitivity in the fine grid-spacing regime (grid spacings ≤2m) is closely related to the reduction in the energy content of large-scale turbulence, leading to less turbulence kinetic energy and hence lower boundary-layer heights. The present work demonstrates that there is still an urgent need to address this grid-sensitivity issue in order to perform reliable LES of the stable boundary layer.

KW - GABLS1

KW - Grid sensitivity

KW - Large-eddy simulation

KW - PALM

KW - Stable boundary layer

UR - http://www.scopus.com/inward/record.url?scp=85113707312&partnerID=8YFLogxK

U2 - 10.1007/s10546-021-00656-8

DO - 10.1007/s10546-021-00656-8

M3 - Article

AN - SCOPUS:85113707312

VL - 182

SP - 251

EP - 273

JO - Boundary-Layer Meteorology

JF - Boundary-Layer Meteorology

SN - 0006-8314

IS - 2

ER -