Changeset 109 for trunk/documentation
- Timestamp:
- Apr 14, 2011, 11:47:04 AM (14 years ago)
- Location:
- trunk/documentation
- Files:
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- 1 added
- 1 copied
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TabularUnified trunk/documentation/disvert.tex ¶
r108 r109 33 33 \vspace{1cm} 34 34 \Large 35 The upper boundary sponge layer35 The vertical discretization 36 36 } 37 37 … … 43 43 \end{center} 44 44 45 %\section{Theoretical aspects} 45 46 \section{Theoretical aspects} 47 48 The position of the layers: 49 \begin{itemize} 50 \item pressure limit between two layers, 51 \item pressure within the layers 52 \end{itemize} 53 54 The Exner function: definition. 55 It corresponds to the pressure levels within the layers. 56 Used for the computation of the potential temperature. 57 For the Earth, we use a specific scheme that computes these positions so that 58 it maintains a condition of proportionality between total, 59 internal and potential energy (cf. a note from F. Hourdin). 46 60 47 61 \section{Pratical aspects in the code} 48 62 49 The sponge layer is applied at the upper boundary when the \textsf{ok\_strato} 50 flag is set to {\em True} in \textsf{gcm.def} 51 (this parameter also controls the application of a second step in the 52 horizontal dissipation). 63 \begin{itemize} 64 \item \textsf{disvert\_[no]terre.F[90]}: 65 position of the interface pressure levels from an input file 66 (several possibilities). 67 Definition of ap, bp and presnivs. 68 In the planetary version, definition of aps and bps. 53 69 54 The tendencies for the upper boundary sponge layer are computed separately in 55 the \textsf{top\_bound.F} routine, called from \textsf{leapfrog.F}. 56 These tendencies are \textsf{dutop}, \textsf{dvtop} and \textsf{dhtop}, in 57 unit/s. 70 This is done only once, called at the beginning from \textsf{iniconst.F}. 58 71 59 Three parameters may be adjusted in the \textsf{gcm.def} file: 60 \begin{itemize} 61 \item \textsf{iflag\_top\_bound}: selects the affected layers. 62 \begin{itemize} 63 \item 1: only the top 4 layers are affected. In this case, the damping rate 64 is divided by 2 in the second layer, 4 in the third and 8 in the fourth. 65 \item 2: layers with pressure lower than 100 times the top pressure. 66 In this case, the damping rate depends linearly on the pressure. 67 \end{itemize} 68 \item \textsf{mode\_top\_bound}: selects how the fields are affected. 69 \begin{itemize} 70 \item 0: No sponge layer is applied. 71 \item 1: Zonal and meridional winds are damped to zero. 72 \item 2: Zonal and meridional winds are damped to their zonally averaged value. 73 \item 3: Temperature, zonal and meridional winds are damped to their zonally 74 averaged value. 75 \end{itemize} 76 \item \textsf{tau\_top\_bound}: damping rate (in /s) in the top layer. 72 \item Interface pressures: 73 computed in \textsf{caldyn0.F, caldyn.F, integrd.F, leapfrog.F} 74 through the \textsf{pression.F} routine. 75 76 \item Exner function (and therefore pressure within the layers): 77 computed at three different places in \textsf{leapfrog.F} through the 78 \textsf{exner\_[hyb/milieu].F} routine. 79 For the Earth, we use \textsf{exner\_hyb.F}, that computes the positions in a 80 specific way to maintain a condition of proportionality between total, 81 internal and potential energy (cf. a note from F. Hourdin). 82 For other planets, we use \textsf{exner\_milieu.F}, that computes the positions 83 of these pressure levels exactly in the middle of each layer. 84 Though this fails to maintain the previous condition, there is no evidence of 85 any significant influence on the results, and it makes it a lot easier to 86 define correctly the level positions with the input file. 77 87 \end{itemize} 78 88
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