Changeset 6306 for branches/2015
- Timestamp:
- 2016-02-11T18:48:18+01:00 (8 years ago)
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branches/2015/nemo_v3_6_STABLE/DOC/TexFiles/Chapters/Chap_ZDF.tex
r6275 r6306 261 261 \end{equation} 262 262 263 At the ocean surface, a non zero length scale is set through the \np{rn\_ lmin0} namelist263 At the ocean surface, a non zero length scale is set through the \np{rn\_mxl0} namelist 264 264 parameter. Usually the surface scale is given by $l_o = \kappa \,z_o$ 265 265 where $\kappa = 0.4$ is von Karman's constant and $z_o$ the roughness 266 266 parameter of the surface. Assuming $z_o=0.1$~m \citep{Craig_Banner_JPO94} 267 leads to a 0.04~m, the default value of \np{rn\_ lsurf}. In the ocean interior267 leads to a 0.04~m, the default value of \np{rn\_mxl0}. In the ocean interior 268 268 a minimum length scale is set to recover the molecular viscosity when $\bar{e}$ 269 269 reach its minimum value ($1.10^{-6}= C_k\, l_{min} \,\sqrt{\bar{e}_{min}}$ ). … … 294 294 As the surface boundary condition on TKE is prescribed through $\bar{e}_o = e_{bb} |\tau| / \rho_o$, 295 295 with $e_{bb}$ the \np{rn\_ebb} namelist parameter, setting \np{rn\_ebb}~=~67.83 corresponds 296 to $\alpha_{CB} = 100$. further setting \np{ln\_lsurf} to true applies \eqref{ZDF_Lsbc}297 as surface boundary condition on length scale, with $\beta$ hard coded to the Stace t's value.296 to $\alpha_{CB} = 100$. Further setting \np{ln\_mxl0} to true applies \eqref{ZDF_Lsbc} 297 as surface boundary condition on length scale, with $\beta$ hard coded to the Stacey's value. 298 298 Note that a minimal threshold of \np{rn\_emin0}$=10^{-4}~m^2.s^{-2}$ (namelist parameters) 299 299 is applied on surface $\bar{e}$ value. … … 939 939 $H = 4000$~m, the resulting friction coefficient is $r = 4\;10^{-4}$~m\;s$^{-1}$. 940 940 This is the default value used in \NEMO. It corresponds to a decay time scale 941 of 115~days. It can be changed by specifying \np{rn\_bfri c1} (namelist parameter).941 of 115~days. It can be changed by specifying \np{rn\_bfri1} (namelist parameter). 942 942 943 943 For the linear friction case the coefficients defined in the general … … 949 949 \end{split} 950 950 \end{equation} 951 When \np{nn\_botfr}=1, the value of $r$ used is \np{rn\_bfri c1}.951 When \np{nn\_botfr}=1, the value of $r$ used is \np{rn\_bfri1}. 952 952 Setting \np{nn\_botfr}=0 is equivalent to setting $r=0$ and leads to a free-slip 953 953 bottom boundary condition. These values are assigned in \mdl{zdfbfr}. … … 956 956 in the \ifile{bfr\_coef} input NetCDF file. The mask values should vary from 0 to 1. 957 957 Locations with a non-zero mask value will have the friction coefficient increased 958 by $mask\_value$*\np{rn\_bfrien}*\np{rn\_bfri c1}.958 by $mask\_value$*\np{rn\_bfrien}*\np{rn\_bfri1}. 959 959 960 960 % ------------------------------------------------------------------------------------------------------------- … … 976 976 $e_b = 2.5\;10^{-3}$m$^2$\;s$^{-2}$, while the FRAM experiment \citep{Killworth1992} 977 977 uses $C_D = 1.4\;10^{-3}$ and $e_b =2.5\;\;10^{-3}$m$^2$\;s$^{-2}$. 978 The CME choices have been set as default values (\np{rn\_bfri c2} and \np{rn\_bfeb2}978 The CME choices have been set as default values (\np{rn\_bfri2} and \np{rn\_bfeb2} 979 979 namelist parameters). 980 980 … … 991 991 \end{equation} 992 992 993 The coefficients that control the strength of the non-linear bottom friction are 994 initialised as namelist parameters: $C_D$= \np{rn\_bfri2}, and $e_b$ =\np{rn\_bfeb2}. 995 Note for applications which treat tides explicitly a low or even zero value of 996 \np{rn\_bfeb2} is recommended. From v3.2 onwards a local enhancement of $C_D$ 997 is possible via an externally defined 2D mask array (\np{ln\_bfr2d}=true). 998 See previous section for details. 993 The coefficients that control the strength of the non-linear bottom friction are 994 initialised as namelist parameters: $C_D$= \np{rn\_bfri2}, and $e_b$ =\np{rn\_bfeb2}. 995 Note for applications which treat tides explicitly a low or even zero value of 996 \np{rn\_bfeb2} is recommended. From v3.2 onwards a local enhancement of $C_D$ is possible 997 via an externally defined 2D mask array (\np{ln\_bfr2d}=true). This works in the same way 998 as for the linear bottom friction case with non-zero masked locations increased by 999 $mask\_value$*\np{rn\_bfrien}*\np{rn\_bfri2}. 1000 1001 % ------------------------------------------------------------------------------------------------------------- 1002 % Bottom Friction Log-layer 1003 % ------------------------------------------------------------------------------------------------------------- 1004 \subsection{Log-layer Bottom Friction enhancement (\np{nn\_botfr} = 2, \np{ln\_loglayer} = .true.)} 1005 \label{ZDF_bfr_loglayer} 1006 1007 In the non-linear bottom friction case, the drag coefficient, $C_D$, can be optionally 1008 enhanced using a "law of the wall" scaling. If \np{ln\_loglayer} = .true., $C_D$ is no 1009 longer constant but is related to the thickness of the last wet layer in each column by: 1010 1011 \begin{equation} 1012 C_D = \left ( {\kappa \over {\rm log}\left ( 0.5e_{3t}/rn\_bfrz0 \right ) } \right )^2 1013 \end{equation} 1014 1015 \noindent where $\kappa$ is the von-Karman constant and \np{rn\_bfrz0} is a roughness 1016 length provided via the namelist. 1017 1018 For stability, the drag coefficient is bounded such that it is kept greater or equal to 1019 the base \np{rn\_bfri2} value and it is not allowed to exceed the value of an additional 1020 namelist parameter: \np{rn\_bfri2\_max}, i.e.: 1021 1022 \begin{equation} 1023 rn\_bfri2 \leq C_D \leq rn\_bfri2\_max 1024 \end{equation} 1025 1026 \noindent Note also that a log-layer enhancement can also be applied to the top boundary 1027 friction if under ice-shelf cavities are in use (\np{ln\_isfcav}=.true.). In this case, the 1028 relevant namelist parameters are \np{rn\_tfrz0}, \np{rn\_tfri2} 1029 and \np{rn\_tfri2\_max}. 999 1030 1000 1031 % -------------------------------------------------------------------------------------------------------------
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