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Titel |
Numerical study of buoyancy reversal in stably stratified flows |
VerfasserIn |
H. Schmidt, J. P. Mellado, N. Peters, A. R. Kerstein, B. Stevens |
Konferenz |
EGU General Assembly 2009
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 11 (2009) |
Datensatznummer |
250023909
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Zusammenfassung |
Recent work suggests that shallow cumulus convection is the major point of departure among
climate-model representations of climate sensitivity. A characteristic feature of the
stratocumulus-topped boundary layer (STBL) is the contact discontinuity, and accompanying
sharp temperature inversion, that separates the top of the cloud from the overlying
quasi-laminar, free troposphere. This temperature inversion resists the tendency of the
underlying turbulent layer to grow through entrainment into the free-troposphere, which
allows the lower layer to moisten and clouds to develop therein. This sharp transition and the
importance of the mixing between the two layers, greatly frustrates attempts to represent
the STBL numerically, e.g. via large eddy simulation (LES), due to insufficient
resolution.
The subtile small scale interaction of molecular effects and turbulence might only
be accessed using direct numerical simulation (DNS) and stochastic turbulence
models where the latter keep full resolution of physical processes at least in one
dimension.
First we will present results of a stochastic one-dimensional mixing model used
to explore laboratory analogs to the cloud top mixing problem. Here radiatively
induced buoyancy reversal is investigated. Further we explore the buoyancy reversal
problem using 2D and 3D DNS. The basic configuration now is a two-layer system,
stably stratified because of the temperature difference between the two layers but
undergoing evaporative cooling in the mixing regions, which may lead to buoyancy
reversal. |
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