MMM SEMINAR NCAR
Entrainment processes at the
top of the convectively-driven boundary layer revisited through high-resolution
large-eddy simulation and Lagrangian
stochastic models
Charles Chemel
Laboratory of Geophysical
and Industrial Fluid Flows
CNRS/UJF/INPG
In this study, convective entrainment into a stably-stratified atmosphere is
discussed. The discussion is based on results from a high-resolution (2563
grid points) large-eddy simulation (LES) of the convectively-driven
(shear-free) boundary layer (CBL) over flat terrain initialized by a commonly
used sounding of Day 33 of the Wangara experiment. This ‘realistic’
initialization enables us to validate further the numerical results. The
mixed-layer dynamics, which forces the interfacial layer between the CBL and
the free atmosphere, is detailed from a deterministic point of view (using the
Q-criterion to identify the organized turbulent structures) and a statistical
point of view (by computing 1D and 2D spatial as well as temporal spectra). The
entrainment law is next discussed using an Eulerian approach (i.e. the
LES) and a Lagrangian approach (i.e. a Lagrangian stochastic model coupled with
the LES).
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