TY - JOUR

T1 - Analysis of pressure-strain and pressure gradient-scalar covariances in cloud-topped boundary layers

T2 - A large-eddy simulation study

AU - Heinze, Rieke

AU - Mironov, Dmitrii

AU - Raasch, Siegfried

N1 - Funding Information: The authors thank two anonymous reviewers and G. J. Firl whose comments helped to improve the manuscript. This study was supported by the Extramurale Forschung Program of the German Weather Service and partially supported by the European Commission through the COST Action ES0905. All simulations were performed on the SGI Altix ICE of The North-German Supercomputing Alliance (HRLN), Hannover and Berlin, Germany. The NCAR Command Language (Version 6.2.1, http://dx.doi.org/10. 5065/D6WD3XH5) was used for analysis and visualization. Primary data and scripts used in the analysis and other supplementary information that may be useful in reproducing the author's work are archived by the Max Planck Institute for Meteorology and can be obtained by contacting publications@mpimet.mpg.de. The LES data used in this paper can be obtained from the first author, upon request.

PY - 2016/4/22

Y1 - 2016/4/22

N2 - A detailed analysis of the pressure-scrambling terms (i.e., the pressure-strain and pressure gradient-scalar covariances) in the Reynolds-stress and scalar-flux budgets for cloud-topped boundary layers (CTBLs) is performed using high-resolution large-eddy simulation (LES). Two CTBLs are simulated - one with trade wind shallow cumuli, and the other with nocturnal marine stratocumuli. The pressure-scrambling terms are decomposed into contributions due to turbulence-turbulence interactions, mean velocity shear, buoyancy, and Coriolis effects. Commonly used models of these contributions, including a simple linear model most often used in geophysical applications and a more sophisticated two-component-limit (TCL) nonlinear model, are tested against the LES data. The decomposition of the pressure-scrambling terms shows that the turbulence-turbulence and buoyancy contributions are most significant for cloud-topped boundary layers. The Coriolis contribution is negligible. The shear contribution is generally of minor importance inside the cloudy layers, but it is the leading-order contribution near the surface. A comparison of models of the pressure-scrambling terms with the LES data suggests that the more complex TCL model is superior to the simple linear model only for a few contributions. The linear model is able to reproduce the principal features of the pressure-scrambling terms reasonably well. It can be applied in the second-order turbulence modeling of cloud-topped boundary layer flows, provided some uncertainties are tolerated.

AB - A detailed analysis of the pressure-scrambling terms (i.e., the pressure-strain and pressure gradient-scalar covariances) in the Reynolds-stress and scalar-flux budgets for cloud-topped boundary layers (CTBLs) is performed using high-resolution large-eddy simulation (LES). Two CTBLs are simulated - one with trade wind shallow cumuli, and the other with nocturnal marine stratocumuli. The pressure-scrambling terms are decomposed into contributions due to turbulence-turbulence interactions, mean velocity shear, buoyancy, and Coriolis effects. Commonly used models of these contributions, including a simple linear model most often used in geophysical applications and a more sophisticated two-component-limit (TCL) nonlinear model, are tested against the LES data. The decomposition of the pressure-scrambling terms shows that the turbulence-turbulence and buoyancy contributions are most significant for cloud-topped boundary layers. The Coriolis contribution is negligible. The shear contribution is generally of minor importance inside the cloudy layers, but it is the leading-order contribution near the surface. A comparison of models of the pressure-scrambling terms with the LES data suggests that the more complex TCL model is superior to the simple linear model only for a few contributions. The linear model is able to reproduce the principal features of the pressure-scrambling terms reasonably well. It can be applied in the second-order turbulence modeling of cloud-topped boundary layer flows, provided some uncertainties are tolerated.

KW - cloud-topped boundary layers

KW - large-eddy simulation

KW - parameterizations

KW - pressure-scrambling terms

KW - second-order turbulence modeling

UR - http://www.scopus.com/inward/record.url?scp=84953775181&partnerID=8YFLogxK

U2 - 10.1002/2015MS000508

DO - 10.1002/2015MS000508

M3 - Article

AN - SCOPUS:84953775181

VL - 8

SP - 3

EP - 30

JO - Journal of Advances in Modeling Earth Systems

JF - Journal of Advances in Modeling Earth Systems

SN - 1942-2466

IS - 1

ER -