Large-eddy simulation in an anelastic framework with closed water and entropy balances
A large-eddy simulation (LES) framework is developed for simulating the dynamics of clouds and boundary layers with closed water and entropy balances. The framework is based on the anelastic equations in a formulation that remains accurate for deep convection. As prognostic variables, it uses total water and entropy, which are conserved in adiabatic and reversible processes, including reversible phase changes of water. This has numerical advantages for modeling clouds, in which reversible phase changes of water occur frequently. The equations of motion are discretized using higher-order weighted essentially nonoscillatory (WENO) discretization schemes with strong stability preserving time stepping. Numerical tests demonstrate that the WENO schemes yield simulations superior to centered schemes, even when the WENO schemes are used at coarser resolution. The framework is implemented in a new LES code written in Python and Cython, which makes the code transparent and easy to use for a wide user group.
© 2015 The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. Received 9 JUN 2015; Accepted 20 AUG 2015; Accepted article online 22 AUG 2015; Published online 26 SEP 2015. This work was supported by the U.S. National Science Foundation (grants ARC-1107795 and CCF-1048575), by Caltech's Terrestrial Hazard Observation and Reporting (THOR) Center, and by the Swiss National Science Foundation. We thank João Teixeira for stimulating discussions and Cheikh Mbengue, Bettina Meyer, David Raymond, and Sally Zhang for their help and suggestions during the development of PyCLES. The PyCLES code is freely available at climate-dynamics.org/software.
||1.7 MB||Preview Download|