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

A large-eddy simulation study

authored by: Rieke Heinze, Dmitrii Mironov, Siegfried Raasch
Abstract: 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.
Organisation(s): Institute of Meteorology and Climatology
External Organisation(s): Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.V. (MPG)
Deutscher Wetterdienst (DWD)
Type: Article
Journal: Journal of Advances in Modeling Earth Systems
Volume: 8
Pages: 3-30
No. of pages: 28
ISSN: 1942-2466
Publication date: 22.04.2016
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Global and Planetary Change, Environmental Chemistry, General Earth and Planetary Sciences
Sustainable Development Goals: SDG 14 - Life Below Water
Electronic version(s): https://doi.org/10.1002/2015MS000508 (Access: Open)