Changeset 10419 for NEMO/branches/2018/dev_r10164_HPC09_ESIWACE_PREP_MERGE/doc/latex/NEMO/subfiles/chap_ZDF.tex
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r10368 r10419 1 \documentclass[../tex_main/NEMO_manual]{subfiles} 1 \documentclass[../main/NEMO_manual]{subfiles} 2 2 3 \begin{document} 3 4 % ================================================================ … … 6 7 \chapter{Vertical Ocean Physics (ZDF)} 7 8 \label{chap:ZDF} 9 8 10 \minitoc 9 11 10 12 %gm% Add here a small introduction to ZDF and naming of the different physics (similar to what have been written for TRA and DYN. 11 13 12 13 14 \newpage 14 $\ $\newline % force a new ligne15 16 15 17 16 % ================================================================ … … 60 59 It is recommended that this option is only used in process studies, not in basin scale simulations. 61 60 Typical values used in this case are: 62 \begin{align*} 63 A_u^{vm} = A_v^{vm} &= 1.2\ 10^{-4}~m^2.s^{-1} \\64 A^{vT} = A^{vS} &= 1.2\ 10^{-5}~m^2.s^{-1}61 \begin{align*} 62 A_u^{vm} = A_v^{vm} &= 1.2\ 10^{-4}~m^2.s^{-1} \\ 63 A^{vT} = A^{vS} &= 1.2\ 10^{-5}~m^2.s^{-1} 65 64 \end{align*} 66 65 … … 69 68 that is $\sim10^{-6}~m^2.s^{-1}$ for momentum, $\sim10^{-7}~m^2.s^{-1}$ for temperature and 70 69 $\sim10^{-9}~m^2.s^{-1}$ for salinity. 71 72 70 73 71 % ------------------------------------------------------------------------------------------------------------- … … 90 88 ($i.e.$ the ratio of stratification to vertical shear). 91 89 Following \citet{Pacanowski_Philander_JPO81}, the following formulation has been implemented: 92 \begin{equation} \label{eq:zdfric} 93 \left\{ \begin{aligned} 94 A^{vT} &= \frac {A_{ric}^{vT}}{\left( 1+a \; Ri \right)^n} + A_b^{vT} \\ 95 A^{vm} &= \frac{A^{vT} }{\left( 1+ a \;Ri \right) } + A_b^{vm} 96 \end{aligned} \right. 97 \end{equation} 90 \[ 91 % \label{eq:zdfric} 92 \left\{ 93 \begin{aligned} 94 A^{vT} &= \frac {A_{ric}^{vT}}{\left( 1+a \; Ri \right)^n} + A_b^{vT} \\ 95 A^{vm} &= \frac{A^{vT} }{\left( 1+ a \;Ri \right) } + A_b^{vm} 96 \end{aligned} 97 \right. 98 \] 98 99 where $Ri = N^2 / \left(\partial_z \textbf{U}_h \right)^2$ is the local Richardson number, 99 100 $N$ is the local Brunt-Vais\"{a}l\"{a} frequency (see \autoref{subsec:TRA_bn2}), … … 111 112 112 113 This depth is assumed proportional to the "depth of frictional influence" that is limited by rotation: 113 \ begin{equation}114 h_{e} = Ek \frac {u^{*}} {f_{0}}115 \ end{equation}114 \[ 115 h_{e} = Ek \frac {u^{*}} {f_{0}} 116 \] 116 117 where, $Ek$ is an empirical parameter, $u^{*}$ is the friction velocity and $f_{0}$ is the Coriolis parameter. 117 118 118 119 In this similarity height relationship, the turbulent friction velocity: 119 \ begin{equation}120 u^{*} = \sqrt \frac {|\tau|} {\rho_o}121 \ end{equation}120 \[ 121 u^{*} = \sqrt \frac {|\tau|} {\rho_o} 122 \] 122 123 is computed from the wind stress vector $|\tau|$ and the reference density $ \rho_o$. 123 124 The final $h_{e}$ is further constrained by the adjustable bounds \np{rn\_mldmin} and \np{rn\_mldmax}. … … 146 147 The time evolution of $\bar{e}$ is the result of the production of $\bar{e}$ through vertical shear, 147 148 its destruction through stratification, its vertical diffusion, and its dissipation of \citet{Kolmogorov1942} type: 148 \begin{equation} \label{eq:zdftke_e} 149 \frac{\partial \bar{e}}{\partial t} = 150 \frac{K_m}{{e_3}^2 }\;\left[ {\left( {\frac{\partial u}{\partial k}} \right)^2 151 +\left( {\frac{\partial v}{\partial k}} \right)^2} \right] 152 -K_\rho\,N^2 153 +\frac{1}{e_3} \;\frac{\partial }{\partial k}\left[ {\frac{A^{vm}}{e_3 } 154 \;\frac{\partial \bar{e}}{\partial k}} \right] 155 - c_\epsilon \;\frac{\bar {e}^{3/2}}{l_\epsilon } 149 \begin{equation} 150 \label{eq:zdftke_e} 151 \frac{\partial \bar{e}}{\partial t} = 152 \frac{K_m}{{e_3}^2 }\;\left[ {\left( {\frac{\partial u}{\partial k}} \right)^2 153 +\left( {\frac{\partial v}{\partial k}} \right)^2} \right] 154 -K_\rho\,N^2 155 +\frac{1}{e_3} \;\frac{\partial }{\partial k}\left[ {\frac{A^{vm}}{e_3 } 156 \;\frac{\partial \bar{e}}{\partial k}} \right] 157 - c_\epsilon \;\frac{\bar {e}^{3/2}}{l_\epsilon } 156 158 \end{equation} 157 \begin{equation} \label{eq:zdftke_kz} 158 \begin{split} 159 K_m &= C_k\ l_k\ \sqrt {\bar{e}\; } \\ 160 K_\rho &= A^{vm} / P_{rt} 161 \end{split} 162 \end{equation} 159 \[ 160 % \label{eq:zdftke_kz} 161 \begin{split} 162 K_m &= C_k\ l_k\ \sqrt {\bar{e}\; } \\ 163 K_\rho &= A^{vm} / P_{rt} 164 \end{split} 165 \] 163 166 where $N$ is the local Brunt-Vais\"{a}l\"{a} frequency (see \autoref{subsec:TRA_bn2}), 164 167 $l_{\epsilon }$ and $l_{\kappa }$ are the dissipation and mixing length scales, … … 168 171 They are set through namelist parameters \np{nn\_ediff} and \np{nn\_ediss}. 169 172 $P_{rt}$ can be set to unity or, following \citet{Blanke1993}, be a function of the local Richardson number, $R_i$: 170 \begin{align*} \label{eq:prt} 171 P_{rt} = \begin{cases} 172 \ \ \ 1 & \text{if $\ R_i \leq 0.2$} \\ 173 5\,R_i & \text{if $\ 0.2 \leq R_i \leq 2$} \\ 174 \ \ 10 & \text{if $\ 2 \leq R_i$} 175 \end{cases} 173 \begin{align*} 174 % \label{eq:prt} 175 P_{rt} = 176 \begin{cases} 177 \ \ \ 1 & \text{if $\ R_i \leq 0.2$} \\ 178 5\,R_i & \text{if $\ 0.2 \leq R_i \leq 2$} \\ 179 \ \ 10 & \text{if $\ 2 \leq R_i$} 180 \end{cases} 176 181 \end{align*} 177 182 Options are defined through the \ngn{namzdfy\_tke} namelist variables. … … 195 200 196 201 \subsubsection{Turbulent length scale} 202 197 203 For computational efficiency, the original formulation of the turbulent length scales proposed by 198 204 \citet{Gaspar1990} has been simplified. 199 205 Four formulations are proposed, the choice of which is controlled by the \np{nn\_mxl} namelist parameter. 200 206 The first two are based on the following first order approximation \citep{Blanke1993}: 201 \begin{equation} \label{eq:tke_mxl0_1} 202 l_k = l_\epsilon = \sqrt {2 \bar{e}\; } / N 207 \begin{equation} 208 \label{eq:tke_mxl0_1} 209 l_k = l_\epsilon = \sqrt {2 \bar{e}\; } / N 203 210 \end{equation} 204 211 which is valid in a stable stratified region with constant values of the Brunt-Vais\"{a}l\"{a} frequency. … … 211 218 which add an extra assumption concerning the vertical gradient of the computed length scale. 212 219 So, the length scales are first evaluated as in \autoref{eq:tke_mxl0_1} and then bounded such that: 213 \begin{equation} \label{eq:tke_mxl_constraint} 214 \frac{1}{e_3 }\left| {\frac{\partial l}{\partial k}} \right| \leq 1 215 \qquad \text{with }\ l = l_k = l_\epsilon 220 \begin{equation} 221 \label{eq:tke_mxl_constraint} 222 \frac{1}{e_3 }\left| {\frac{\partial l}{\partial k}} \right| \leq 1 223 \qquad \text{with }\ l = l_k = l_\epsilon 216 224 \end{equation} 217 225 \autoref{eq:tke_mxl_constraint} means that the vertical variations of the length scale cannot be larger than … … 227 235 (and note that here we use numerical indexing): 228 236 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 229 \begin{figure}[!t] \begin{center} 230 \includegraphics[width=1.00\textwidth]{Fig_mixing_length} 231 \caption{ \protect\label{fig:mixing_length} 232 Illustration of the mixing length computation. } 233 \end{center} 237 \begin{figure}[!t] 238 \begin{center} 239 \includegraphics[width=1.00\textwidth]{Fig_mixing_length} 240 \caption{ 241 \protect\label{fig:mixing_length} 242 Illustration of the mixing length computation. 243 } 244 \end{center} 234 245 \end{figure} 235 246 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 236 \begin{equation} \label{eq:tke_mxl2} 237 \begin{aligned} 238 l_{up\ \ }^{(k)} &= \min \left( l^{(k)} \ , \ l_{up}^{(k+1)} + e_{3t}^{(k)}\ \ \ \; \right) 247 \[ 248 % \label{eq:tke_mxl2} 249 \begin{aligned} 250 l_{up\ \ }^{(k)} &= \min \left( l^{(k)} \ , \ l_{up}^{(k+1)} + e_{3t}^{(k)}\ \ \ \; \right) 239 251 \quad &\text{ from $k=1$ to $jpk$ }\ \\ 240 l_{dwn}^{(k)} &= \min \left( l^{(k)} \ , \ l_{dwn}^{(k-1)} + e_{3t}^{(k-1)} \right)252 l_{dwn}^{(k)} &= \min \left( l^{(k)} \ , \ l_{dwn}^{(k-1)} + e_{3t}^{(k-1)} \right) 241 253 \quad &\text{ from $k=jpk$ to $1$ }\ \\ 242 \end{aligned}243 \ end{equation}254 \end{aligned} 255 \] 244 256 where $l^{(k)}$ is computed using \autoref{eq:tke_mxl0_1}, $i.e.$ $l^{(k)} = \sqrt {2 {\bar e}^{(k)} / {N^2}^{(k)} }$. 245 257 … … 247 259 $ l_k= l_\epsilon = \min \left(\ l_{up} \;,\; l_{dwn}\ \right)$, while in the \np{nn\_mxl}\forcode{ = 3} case, 248 260 the dissipation and mixing turbulent length scales are give as in \citet{Gaspar1990}: 249 \begin{equation} \label{eq:tke_mxl_gaspar} 250 \begin{aligned} 251 & l_k = \sqrt{\ l_{up} \ \ l_{dwn}\ } \\ 252 & l_\epsilon = \min \left(\ l_{up} \;,\; l_{dwn}\ \right) 253 \end{aligned} 254 \end{equation} 261 \[ 262 % \label{eq:tke_mxl_gaspar} 263 \begin{aligned} 264 & l_k = \sqrt{\ l_{up} \ \ l_{dwn}\ } \\ 265 & l_\epsilon = \min \left(\ l_{up} \;,\; l_{dwn}\ \right) 266 \end{aligned} 267 \] 255 268 256 269 At the ocean surface, a non zero length scale is set through the \np{rn\_mxl0} namelist parameter. … … 261 274 $\bar{e}$ reach its minimum value ($1.10^{-6}= C_k\, l_{min} \,\sqrt{\bar{e}_{min}}$ ). 262 275 263 264 276 \subsubsection{Surface wave breaking parameterization} 265 277 %-----------------------------------------------------------------------% 278 266 279 Following \citet{Mellor_Blumberg_JPO04}, the TKE turbulence closure model has been modified to 267 280 include the effect of surface wave breaking energetics. … … 272 285 273 286 Following \citet{Craig_Banner_JPO94}, the boundary condition on surface TKE value is : 274 \begin{equation} \label{eq:ZDF_Esbc} 275 \bar{e}_o = \frac{1}{2}\,\left( 15.8\,\alpha_{CB} \right)^{2/3} \,\frac{|\tau|}{\rho_o} 287 \begin{equation} 288 \label{eq:ZDF_Esbc} 289 \bar{e}_o = \frac{1}{2}\,\left( 15.8\,\alpha_{CB} \right)^{2/3} \,\frac{|\tau|}{\rho_o} 276 290 \end{equation} 277 291 where $\alpha_{CB}$ is the \citet{Craig_Banner_JPO94} constant of proportionality which depends on the ''wave age'', 278 292 ranging from 57 for mature waves to 146 for younger waves \citep{Mellor_Blumberg_JPO04}. 279 293 The boundary condition on the turbulent length scale follows the Charnock's relation: 280 \begin{equation} \label{eq:ZDF_Lsbc} 281 l_o = \kappa \beta \,\frac{|\tau|}{g\,\rho_o} 294 \begin{equation} 295 \label{eq:ZDF_Lsbc} 296 l_o = \kappa \beta \,\frac{|\tau|}{g\,\rho_o} 282 297 \end{equation} 283 298 where $\kappa=0.40$ is the von Karman constant, and $\beta$ is the Charnock's constant. … … 293 308 surface $\bar{e}$ value. 294 309 295 296 310 \subsubsection{Langmuir cells} 297 311 %--------------------------------------% 312 298 313 Langmuir circulations (LC) can be described as ordered large-scale vertical motions in 299 314 the surface layer of the oceans. … … 313 328 By making an analogy with the characteristic convective velocity scale ($e.g.$, \citet{D'Alessio_al_JPO98}), 314 329 $P_{LC}$ is assumed to be : 315 \ begin{equation}330 \[ 316 331 P_{LC}(z) = \frac{w_{LC}^3(z)}{H_{LC}} 317 \ end{equation}332 \] 318 333 where $w_{LC}(z)$ is the vertical velocity profile of LC, and $H_{LC}$ is the LC depth. 319 334 With no information about the wave field, $w_{LC}$ is assumed to be proportional to … … 322 337 $u_s = 0.016 \,|U_{10m}|$. 323 338 Assuming an air density of $\rho_a=1.22 \,Kg/m^3$ and a drag coefficient of 324 $1.5~10^{-3}$ give the expression used of $u_s$ as a function of the module of surface stress}. 339 $1.5~10^{-3}$ give the expression used of $u_s$ as a function of the module of surface stress 340 }. 325 341 For the vertical variation, $w_{LC}$ is assumed to be zero at the surface as well as at 326 342 a finite depth $H_{LC}$ (which is often close to the mixed layer depth), 327 343 and simply varies as a sine function in between (a first-order profile for the Langmuir cell structures). 328 344 The resulting expression for $w_{LC}$ is : 329 \begin{equation} 330 w_{LC} = \begin{cases} 331 c_{LC} \,u_s \,\sin(- \pi\,z / H_{LC} ) & \text{if $-z \leq H_{LC}$} \\ 332 0 & \text{otherwise} 333 \end{cases} 334 \end{equation} 345 \[ 346 w_{LC} = 347 \begin{cases} 348 c_{LC} \,u_s \,\sin(- \pi\,z / H_{LC} ) & \text{if $-z \leq H_{LC}$} \\ 349 0 & \text{otherwise} 350 \end{cases} 351 \] 335 352 where $c_{LC} = 0.15$ has been chosen by \citep{Axell_JGR02} as a good compromise to fit LES data. 336 353 The chosen value yields maximum vertical velocities $w_{LC}$ of the order of a few centimeters per second. … … 341 358 $H_{LC}$ is depth to which a water parcel with kinetic energy due to Stoke drift can reach on its own by 342 359 converting its kinetic energy to potential energy, according to 343 \ begin{equation}360 \[ 344 361 - \int_{-H_{LC}}^0 { N^2\;z \;dz} = \frac{1}{2} u_s^2 345 \end{equation} 346 362 \] 347 363 348 364 \subsubsection{Mixing just below the mixed layer} … … 362 378 swell and waves is parameterized by \autoref{eq:ZDF_Esbc} the standard TKE surface boundary condition, 363 379 plus a depth depend one given by: 364 \begin{equation} \label{eq:ZDF_Ehtau} 365 S = (1-f_i) \; f_r \; e_s \; e^{-z / h_\tau} 380 \begin{equation} 381 \label{eq:ZDF_Ehtau} 382 S = (1-f_i) \; f_r \; e_s \; e^{-z / h_\tau} 366 383 \end{equation} 367 384 where $z$ is the depth, $e_s$ is TKE surface boundary condition, $f_r$ is the fraction of the surface TKE that … … 380 397 They will be removed in the next release. 381 398 382 383 384 399 % from Burchard et al OM 2008 : 385 400 % the most critical process not reproduced by statistical turbulence models is the activity of … … 390 405 % (e.g. Mellor, 1989; Large et al., 1994; Meier, 2001; Axell, 2002; St. Laurent and Garrett, 2002). 391 406 392 393 394 407 % ------------------------------------------------------------------------------------------------------------- 395 408 % TKE discretization considerations … … 399 412 400 413 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 401 \begin{figure}[!t] \begin{center} 402 \includegraphics[width=1.00\textwidth]{Fig_ZDF_TKE_time_scheme} 403 \caption{ \protect\label{fig:TKE_time_scheme} 404 Illustration of the TKE time integration and its links to the momentum and tracer time integration. } 405 \end{center} 414 \begin{figure}[!t] 415 \begin{center} 416 \includegraphics[width=1.00\textwidth]{Fig_ZDF_TKE_time_scheme} 417 \caption{ 418 \protect\label{fig:TKE_time_scheme} 419 Illustration of the TKE time integration and its links to the momentum and tracer time integration. 420 } 421 \end{center} 406 422 \end{figure} 407 423 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> … … 419 435 the vertical momentum diffusion is obtained by multiplying this quantity by $u^t$ and 420 436 summing the result vertically: 421 \begin{equation} \label{eq:energ1} 422 \begin{split} 423 \int_{-H}^{\eta} u^t \,\partial_z &\left( {K_m}^t \,(\partial_z u)^{t+\rdt} \right) \,dz \\ 424 &= \Bigl[ u^t \,{K_m}^t \,(\partial_z u)^{t+\rdt} \Bigr]_{-H}^{\eta} 425 - \int_{-H}^{\eta}{ {K_m}^t \,\partial_z{u^t} \,\partial_z u^{t+\rdt} \,dz } 426 \end{split} 437 \begin{equation} 438 \label{eq:energ1} 439 \begin{split} 440 \int_{-H}^{\eta} u^t \,\partial_z &\left( {K_m}^t \,(\partial_z u)^{t+\rdt} \right) \,dz \\ 441 &= \Bigl[ u^t \,{K_m}^t \,(\partial_z u)^{t+\rdt} \Bigr]_{-H}^{\eta} 442 - \int_{-H}^{\eta}{ {K_m}^t \,\partial_z{u^t} \,\partial_z u^{t+\rdt} \,dz } 443 \end{split} 427 444 \end{equation} 428 445 Here, the vertical diffusion of momentum is discretized backward in time with a coefficient, $K_m$, … … 443 460 The rate of change of potential energy (in 1D for the demonstration) due vertical mixing is obtained by 444 461 multiplying vertical density diffusion tendency by $g\,z$ and and summing the result vertically: 445 \begin{equation} \label{eq:energ2} 446 \begin{split} 447 \int_{-H}^{\eta} g\,z\,\partial_z &\left( {K_\rho}^t \,(\partial_k \rho)^{t+\rdt} \right) \,dz \\ 448 &= \Bigl[ g\,z \,{K_\rho}^t \,(\partial_z \rho)^{t+\rdt} \Bigr]_{-H}^{\eta} 449 - \int_{-H}^{\eta}{ g \,{K_\rho}^t \,(\partial_k \rho)^{t+\rdt} } \,dz \\ 450 &= - \Bigl[ z\,{K_\rho}^t \,(N^2)^{t+\rdt} \Bigr]_{-H}^{\eta} 451 + \int_{-H}^{\eta}{ \rho^{t+\rdt} \, {K_\rho}^t \,(N^2)^{t+\rdt} \,dz } 452 \end{split} 462 \begin{equation} 463 \label{eq:energ2} 464 \begin{split} 465 \int_{-H}^{\eta} g\,z\,\partial_z &\left( {K_\rho}^t \,(\partial_k \rho)^{t+\rdt} \right) \,dz \\ 466 &= \Bigl[ g\,z \,{K_\rho}^t \,(\partial_z \rho)^{t+\rdt} \Bigr]_{-H}^{\eta} 467 - \int_{-H}^{\eta}{ g \,{K_\rho}^t \,(\partial_k \rho)^{t+\rdt} } \,dz \\ 468 &= - \Bigl[ z\,{K_\rho}^t \,(N^2)^{t+\rdt} \Bigr]_{-H}^{\eta} 469 + \int_{-H}^{\eta}{ \rho^{t+\rdt} \, {K_\rho}^t \,(N^2)^{t+\rdt} \,dz } 470 \end{split} 453 471 \end{equation} 454 472 where we use $N^2 = -g \,\partial_k \rho / (e_3 \rho)$. … … 468 486 469 487 The above energetic considerations leads to the following final discrete form for the TKE equation: 470 \begin{equation} \label{eq:zdftke_ene} 471 \begin{split} 472 \frac { (\bar{e})^t - (\bar{e})^{t-\rdt} } {\rdt} \equiv 473 \Biggl\{ \Biggr. 474 &\overline{ \left( \left(\overline{K_m}^{\,i+1/2}\right)^{t-\rdt} \,\frac{\delta_{k+1/2}[u^{t+\rdt}]}{{e_3u}^{t+\rdt} } 475 \ \frac{\delta_{k+1/2}[u^ t ]}{{e_3u}^ t } \right) }^{\,i} \\ 476 +&\overline{ \left( \left(\overline{K_m}^{\,j+1/2}\right)^{t-\rdt} \,\frac{\delta_{k+1/2}[v^{t+\rdt}]}{{e_3v}^{t+\rdt} } 477 \ \frac{\delta_{k+1/2}[v^ t ]}{{e_3v}^ t } \right) }^{\,j} 478 \Biggr. \Biggr\} \\ 479 % 480 - &{K_\rho}^{t-\rdt}\,{(N^2)^t} \\ 481 % 482 +&\frac{1}{{e_3w}^{t+\rdt}} \;\delta_{k+1/2} \left[ {K_m}^{t-\rdt} \,\frac{\delta_{k}[(\bar{e})^{t+\rdt}]} {{e_3w}^{t+\rdt}} \right] \\ 483 % 484 - &c_\epsilon \; \left( \frac{\sqrt{\bar {e}}}{l_\epsilon}\right)^{t-\rdt}\,(\bar {e})^{t+\rdt} 485 \end{split} 488 \begin{equation} 489 \label{eq:zdftke_ene} 490 \begin{split} 491 \frac { (\bar{e})^t - (\bar{e})^{t-\rdt} } {\rdt} \equiv 492 \Biggl\{ \Biggr. 493 &\overline{ \left( \left(\overline{K_m}^{\,i+1/2}\right)^{t-\rdt} \,\frac{\delta_{k+1/2}[u^{t+\rdt}]}{{e_3u}^{t+\rdt} } 494 \ \frac{\delta_{k+1/2}[u^ t ]}{{e_3u}^ t } \right) }^{\,i} \\ 495 +&\overline{ \left( \left(\overline{K_m}^{\,j+1/2}\right)^{t-\rdt} \,\frac{\delta_{k+1/2}[v^{t+\rdt}]}{{e_3v}^{t+\rdt} } 496 \ \frac{\delta_{k+1/2}[v^ t ]}{{e_3v}^ t } \right) }^{\,j} 497 \Biggr. \Biggr\} \\ 498 % 499 - &{K_\rho}^{t-\rdt}\,{(N^2)^t} \\ 500 % 501 +&\frac{1}{{e_3w}^{t+\rdt}} \;\delta_{k+1/2} \left[ {K_m}^{t-\rdt} \,\frac{\delta_{k}[(\bar{e})^{t+\rdt}]} {{e_3w}^{t+\rdt}} \right] \\ 502 % 503 - &c_\epsilon \; \left( \frac{\sqrt{\bar {e}}}{l_\epsilon}\right)^{t-\rdt}\,(\bar {e})^{t+\rdt} 504 \end{split} 486 505 \end{equation} 487 506 where the last two terms in \autoref{eq:zdftke_ene} (vertical diffusion and Kolmogorov dissipation) … … 511 530 $k$-$\omega$ \citep{Wilcox_1988} among others \citep{Umlauf_Burchard_JMS03,Kantha_Carniel_CSR05}). 512 531 The GLS scheme is given by the following set of equations: 513 \begin{equation} \label{eq:zdfgls_e} 514 \frac{\partial \bar{e}}{\partial t} = 515 \frac{K_m}{\sigma_e e_3 }\;\left[ {\left( \frac{\partial u}{\partial k} \right)^2 516 +\left( \frac{\partial v}{\partial k} \right)^2} \right] 517 -K_\rho \,N^2 518 +\frac{1}{e_3}\,\frac{\partial}{\partial k} \left[ \frac{K_m}{e_3}\,\frac{\partial \bar{e}}{\partial k} \right] 519 - \epsilon 532 \begin{equation} 533 \label{eq:zdfgls_e} 534 \frac{\partial \bar{e}}{\partial t} = 535 \frac{K_m}{\sigma_e e_3 }\;\left[ {\left( \frac{\partial u}{\partial k} \right)^2 536 +\left( \frac{\partial v}{\partial k} \right)^2} \right] 537 -K_\rho \,N^2 538 +\frac{1}{e_3}\,\frac{\partial}{\partial k} \left[ \frac{K_m}{e_3}\,\frac{\partial \bar{e}}{\partial k} \right] 539 - \epsilon 520 540 \end{equation} 521 541 522 \begin{equation} \label{eq:zdfgls_psi} 523 \begin{split} 524 \frac{\partial \psi}{\partial t} =& \frac{\psi}{\bar{e}} \left\{ 525 \frac{C_1\,K_m}{\sigma_{\psi} {e_3}}\;\left[ {\left( \frac{\partial u}{\partial k} \right)^2 526 +\left( \frac{\partial v}{\partial k} \right)^2} \right] 527 - C_3 \,K_\rho\,N^2 - C_2 \,\epsilon \,Fw \right\} \\ 528 &+\frac{1}{e_3} \;\frac{\partial }{\partial k}\left[ {\frac{K_m}{e_3 } 529 \;\frac{\partial \psi}{\partial k}} \right]\; 530 \end{split} 531 \end{equation} 532 533 \begin{equation} \label{eq:zdfgls_kz} 534 \begin{split} 535 K_m &= C_{\mu} \ \sqrt {\bar{e}} \ l \\ 536 K_\rho &= C_{\mu'}\ \sqrt {\bar{e}} \ l 537 \end{split} 538 \end{equation} 539 540 \begin{equation} \label{eq:zdfgls_eps} 541 {\epsilon} = C_{0\mu} \,\frac{\bar {e}^{3/2}}{l} \; 542 \end{equation} 542 \[ 543 % \label{eq:zdfgls_psi} 544 \begin{split} 545 \frac{\partial \psi}{\partial t} =& \frac{\psi}{\bar{e}} \left\{ 546 \frac{C_1\,K_m}{\sigma_{\psi} {e_3}}\;\left[ {\left( \frac{\partial u}{\partial k} \right)^2 547 +\left( \frac{\partial v}{\partial k} \right)^2} \right] 548 - C_3 \,K_\rho\,N^2 - C_2 \,\epsilon \,Fw \right\} \\ 549 &+\frac{1}{e_3} \;\frac{\partial }{\partial k}\left[ {\frac{K_m}{e_3 } 550 \;\frac{\partial \psi}{\partial k}} \right]\; 551 \end{split} 552 \] 553 554 \[ 555 % \label{eq:zdfgls_kz} 556 \begin{split} 557 K_m &= C_{\mu} \ \sqrt {\bar{e}} \ l \\ 558 K_\rho &= C_{\mu'}\ \sqrt {\bar{e}} \ l 559 \end{split} 560 \] 561 562 \[ 563 % \label{eq:zdfgls_eps} 564 {\epsilon} = C_{0\mu} \,\frac{\bar {e}^{3/2}}{l} \; 565 \] 543 566 where $N$ is the local Brunt-Vais\"{a}l\"{a} frequency (see \autoref{subsec:TRA_bn2}) and 544 567 $\epsilon$ the dissipation rate. … … 549 572 550 573 %--------------------------------------------------TABLE-------------------------------------------------- 551 \begin{table}[htbp] \begin{center} 552 %\begin{tabular}{cp{70pt}cp{70pt}cp{70pt}cp{70pt}cp{70pt}cp{70pt}c} 553 \begin{tabular}{ccccc} 554 & $k-kl$ & $k-\epsilon$ & $k-\omega$ & generic \\ 555 % & \citep{Mellor_Yamada_1982} & \citep{Rodi_1987} & \citep{Wilcox_1988} & \\ 556 \hline \hline 557 \np{nn\_clo} & \textbf{0} & \textbf{1} & \textbf{2} & \textbf{3} \\ 558 \hline 559 $( p , n , m )$ & ( 0 , 1 , 1 ) & ( 3 , 1.5 , -1 ) & ( -1 , 0.5 , -1 ) & ( 2 , 1 , -0.67 ) \\ 560 $\sigma_k$ & 2.44 & 1. & 2. & 0.8 \\ 561 $\sigma_\psi$ & 2.44 & 1.3 & 2. & 1.07 \\ 562 $C_1$ & 0.9 & 1.44 & 0.555 & 1. \\ 563 $C_2$ & 0.5 & 1.92 & 0.833 & 1.22 \\ 564 $C_3$ & 1. & 1. & 1. & 1. \\ 565 $F_{wall}$ & Yes & -- & -- & -- \\ 566 \hline 567 \hline 568 \end{tabular} 569 \caption{ \protect\label{tab:GLS} 570 Set of predefined GLS parameters, or equivalently predefined turbulence models available with 571 \protect\key{zdfgls} and controlled by the \protect\np{nn\_clos} namelist variable in \protect\ngn{namzdf\_gls}.} 572 \end{center} \end{table} 574 \begin{table}[htbp] 575 \begin{center} 576 % \begin{tabular}{cp{70pt}cp{70pt}cp{70pt}cp{70pt}cp{70pt}cp{70pt}c} 577 \begin{tabular}{ccccc} 578 & $k-kl$ & $k-\epsilon$ & $k-\omega$ & generic \\ 579 % & \citep{Mellor_Yamada_1982} & \citep{Rodi_1987} & \citep{Wilcox_1988} & \\ 580 \hline 581 \hline 582 \np{nn\_clo} & \textbf{0} & \textbf{1} & \textbf{2} & \textbf{3} \\ 583 \hline 584 $( p , n , m )$ & ( 0 , 1 , 1 ) & ( 3 , 1.5 , -1 ) & ( -1 , 0.5 , -1 ) & ( 2 , 1 , -0.67 ) \\ 585 $\sigma_k$ & 2.44 & 1. & 2. & 0.8 \\ 586 $\sigma_\psi$ & 2.44 & 1.3 & 2. & 1.07 \\ 587 $C_1$ & 0.9 & 1.44 & 0.555 & 1. \\ 588 $C_2$ & 0.5 & 1.92 & 0.833 & 1.22 \\ 589 $C_3$ & 1. & 1. & 1. & 1. \\ 590 $F_{wall}$ & Yes & -- & -- & -- \\ 591 \hline 592 \hline 593 \end{tabular} 594 \caption{ 595 \protect\label{tab:GLS} 596 Set of predefined GLS parameters, or equivalently predefined turbulence models available with 597 \protect\key{zdfgls} and controlled by the \protect\np{nn\_clos} namelist variable in \protect\ngn{namzdf\_gls}. 598 } 599 \end{center} 600 \end{table} 573 601 %-------------------------------------------------------------------------------------------------------------- 574 602 … … 646 674 647 675 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 648 \begin{figure}[!htb] \begin{center} 649 \includegraphics[width=0.90\textwidth]{Fig_npc} 650 \caption{ \protect\label{fig:npc} 651 Example of an unstable density profile treated by the non penetrative convective adjustment algorithm. 652 $1^{st}$ step: the initial profile is checked from the surface to the bottom. 653 It is found to be unstable between levels 3 and 4. 654 They are mixed. 655 The resulting $\rho$ is still larger than $\rho$(5): levels 3 to 5 are mixed. 656 The resulting $\rho$ is still larger than $\rho$(6): levels 3 to 6 are mixed. 657 The $1^{st}$ step ends since the density profile is then stable below the level 3. 658 $2^{nd}$ step: the new $\rho$ profile is checked following the same procedure as in $1^{st}$ step: 659 levels 2 to 5 are mixed. 660 The new density profile is checked. 661 It is found stable: end of algorithm.} 662 \end{center} \end{figure} 676 \begin{figure}[!htb] 677 \begin{center} 678 \includegraphics[width=0.90\textwidth]{Fig_npc} 679 \caption{ 680 \protect\label{fig:npc} 681 Example of an unstable density profile treated by the non penetrative convective adjustment algorithm. 682 $1^{st}$ step: the initial profile is checked from the surface to the bottom. 683 It is found to be unstable between levels 3 and 4. 684 They are mixed. 685 The resulting $\rho$ is still larger than $\rho$(5): levels 3 to 5 are mixed. 686 The resulting $\rho$ is still larger than $\rho$(6): levels 3 to 6 are mixed. 687 The $1^{st}$ step ends since the density profile is then stable below the level 3. 688 $2^{nd}$ step: the new $\rho$ profile is checked following the same procedure as in $1^{st}$ step: 689 levels 2 to 5 are mixed. 690 The new density profile is checked. 691 It is found stable: end of algorithm. 692 } 693 \end{center} 694 \end{figure} 663 695 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 664 696 … … 781 813 782 814 Diapycnal mixing of S and T are described by diapycnal diffusion coefficients 783 \begin{align*} % \label{eq:zdfddm_Kz} 784 &A^{vT} = A_o^{vT}+A_f^{vT}+A_d^{vT} \\ 785 &A^{vS} = A_o^{vS}+A_f^{vS}+A_d^{vS} 815 \begin{align*} 816 % \label{eq:zdfddm_Kz} 817 &A^{vT} = A_o^{vT}+A_f^{vT}+A_d^{vT} \\ 818 &A^{vS} = A_o^{vS}+A_f^{vS}+A_d^{vS} 786 819 \end{align*} 787 820 where subscript $f$ represents mixing by salt fingering, $d$ by diffusive convection, … … 792 825 To represent mixing of $S$ and $T$ by salt fingering, we adopt the diapycnal diffusivities suggested by Schmitt 793 826 (1981): 794 \begin{align} \label{eq:zdfddm_f} 795 A_f^{vS} &= \begin{cases} 796 \frac{A^{\ast v}}{1+(R_\rho / R_c)^n } &\text{if $R_\rho > 1$ and $N^2>0$ } \\ 797 0 &\text{otherwise} 798 \end{cases} 799 \\ \label{eq:zdfddm_f_T} 800 A_f^{vT} &= 0.7 \ A_f^{vS} / R_\rho 827 \begin{align} 828 \label{eq:zdfddm_f} 829 A_f^{vS} &= 830 \begin{cases} 831 \frac{A^{\ast v}}{1+(R_\rho / R_c)^n } &\text{if $R_\rho > 1$ and $N^2>0$ } \\ 832 0 &\text{otherwise} 833 \end{cases} 834 \\ \label{eq:zdfddm_f_T} 835 A_f^{vT} &= 0.7 \ A_f^{vS} / R_\rho 801 836 \end{align} 802 837 803 838 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 804 \begin{figure}[!t] \begin{center} 805 \includegraphics[width=0.99\textwidth]{Fig_zdfddm} 806 \caption{ \protect\label{fig:zdfddm} 807 From \citet{Merryfield1999} : 808 (a) Diapycnal diffusivities $A_f^{vT}$ and $A_f^{vS}$ for temperature and salt in regions of salt fingering. 809 Heavy curves denote $A^{\ast v} = 10^{-3}~m^2.s^{-1}$ and thin curves $A^{\ast v} = 10^{-4}~m^2.s^{-1}$; 810 (b) diapycnal diffusivities $A_d^{vT}$ and $A_d^{vS}$ for temperature and salt in regions of diffusive convection. 811 Heavy curves denote the Federov parameterisation and thin curves the Kelley parameterisation. 812 The latter is not implemented in \NEMO. } 813 \end{center} \end{figure} 839 \begin{figure}[!t] 840 \begin{center} 841 \includegraphics[width=0.99\textwidth]{Fig_zdfddm} 842 \caption{ 843 \protect\label{fig:zdfddm} 844 From \citet{Merryfield1999} : 845 (a) Diapycnal diffusivities $A_f^{vT}$ and $A_f^{vS}$ for temperature and salt in regions of salt fingering. 846 Heavy curves denote $A^{\ast v} = 10^{-3}~m^2.s^{-1}$ and thin curves $A^{\ast v} = 10^{-4}~m^2.s^{-1}$; 847 (b) diapycnal diffusivities $A_d^{vT}$ and $A_d^{vS}$ for temperature and salt in regions of 848 diffusive convection. 849 Heavy curves denote the Federov parameterisation and thin curves the Kelley parameterisation. 850 The latter is not implemented in \NEMO. 851 } 852 \end{center} 853 \end{figure} 814 854 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 815 855 … … 820 860 To represent mixing of S and T by diffusive layering, the diapycnal diffusivities suggested by 821 861 Federov (1988) is used: 822 \begin{align} \label{eq:zdfddm_d} 823 A_d^{vT} &= \begin{cases} 824 1.3635 \, \exp{\left( 4.6\, \exp{ \left[ -0.54\,( R_{\rho}^{-1} - 1 ) \right] } \right)} 825 &\text{if $0<R_\rho < 1$ and $N^2>0$ } \\ 826 0 &\text{otherwise} 827 \end{cases} 828 \\ \label{eq:zdfddm_d_S} 829 A_d^{vS} &= \begin{cases} 830 A_d^{vT}\ \left( 1.85\,R_{\rho} - 0.85 \right) 831 &\text{if $0.5 \leq R_\rho<1$ and $N^2>0$ } \\ 832 A_d^{vT} \ 0.15 \ R_\rho 833 &\text{if $\ \ 0 < R_\rho<0.5$ and $N^2>0$ } \\ 834 0 &\text{otherwise} 835 \end{cases} 862 \begin{align} 863 % \label{eq:zdfddm_d} 864 A_d^{vT} &= 865 \begin{cases} 866 1.3635 \, \exp{\left( 4.6\, \exp{ \left[ -0.54\,( R_{\rho}^{-1} - 1 ) \right] } \right)} 867 &\text{if $0<R_\rho < 1$ and $N^2>0$ } \\ 868 0 &\text{otherwise} 869 \end{cases} 870 \nonumber \\ 871 \label{eq:zdfddm_d_S} 872 A_d^{vS} &= 873 \begin{cases} 874 A_d^{vT}\ \left( 1.85\,R_{\rho} - 0.85 \right) &\text{if $0.5 \leq R_\rho<1$ and $N^2>0$ } \\ 875 A_d^{vT} \ 0.15 \ R_\rho &\text{if $\ \ 0 < R_\rho<0.5$ and $N^2>0$ } \\ 876 0 &\text{otherwise} 877 \end{cases} 836 878 \end{align} 837 879 … … 863 905 a condition on the vertical diffusive flux. 864 906 For the bottom boundary layer, one has: 865 \begin{equation} \label{eq:zdfbfr_flux} 866 A^{vm} \left( \partial {\textbf U}_h / \partial z \right) = {{\cal F}}_h^{\textbf U} 867 \end{equation} 907 \[ 908 % \label{eq:zdfbfr_flux} 909 A^{vm} \left( \partial {\textbf U}_h / \partial z \right) = {{\cal F}}_h^{\textbf U} 910 \] 868 911 where ${\cal F}_h^{\textbf U}$ is represents the downward flux of horizontal momentum outside 869 912 the logarithmic turbulent boundary layer (thickness of the order of 1~m in the ocean). … … 878 921 bottom model layer. 879 922 To illustrate this, consider the equation for $u$ at $k$, the last ocean level: 880 \begin{equation} \label{eq:zdfbfr_flux2} 881 \frac{\partial u_k}{\partial t} = \frac{1}{e_{3u}} \left[ \frac{A_{uw}^{vm}}{e_{3uw}} \delta_{k+1/2}\;[u] - {\cal F}^u_h \right] \approx - \frac{{\cal F}^u_{h}}{e_{3u}} 923 \begin{equation} 924 \label{eq:zdfbfr_flux2} 925 \frac{\partial u_k}{\partial t} = \frac{1}{e_{3u}} \left[ \frac{A_{uw}^{vm}}{e_{3uw}} \delta_{k+1/2}\;[u] - {\cal F}^u_h \right] \approx - \frac{{\cal F}^u_{h}}{e_{3u}} 882 926 \end{equation} 883 927 If the bottom layer thickness is 200~m, the Ekman transport will be distributed over that depth. … … 897 941 bottom velocities and geometric values to provide the momentum trend due to bottom friction. 898 942 These coefficients are computed in \mdl{zdfbfr} and generally take the form $c_b^{\textbf U}$ where: 899 \begin{equation} \label{eq:zdfbfr_bdef} 900 \frac{\partial {\textbf U_h}}{\partial t} = 943 \begin{equation} 944 \label{eq:zdfbfr_bdef} 945 \frac{\partial {\textbf U_h}}{\partial t} = 901 946 - \frac{{\cal F}^{\textbf U}_{h}}{e_{3u}} = \frac{c_b^{\textbf U}}{e_{3u}} \;{\textbf U}_h^b 902 947 \end{equation} … … 911 956 The linear bottom friction parameterisation (including the special case of a free-slip condition) assumes that 912 957 the bottom friction is proportional to the interior velocity (i.e. the velocity of the last model level): 913 \begin{equation} \label{eq:zdfbfr_linear} 914 {\cal F}_h^\textbf{U} = \frac{A^{vm}}{e_3} \; \frac{\partial \textbf{U}_h}{\partial k} = r \; \textbf{U}_h^b 915 \end{equation} 958 \[ 959 % \label{eq:zdfbfr_linear} 960 {\cal F}_h^\textbf{U} = \frac{A^{vm}}{e_3} \; \frac{\partial \textbf{U}_h}{\partial k} = r \; \textbf{U}_h^b 961 \] 916 962 where $r$ is a friction coefficient expressed in ms$^{-1}$. 917 963 This coefficient is generally estimated by setting a typical decay time $\tau$ in the deep ocean, … … 927 973 928 974 For the linear friction case the coefficients defined in the general expression \autoref{eq:zdfbfr_bdef} are: 929 \begin{equation} \label{eq:zdfbfr_linbfr_b} 930 \begin{split} 931 c_b^u &= - r\\ 932 c_b^v &= - r\\ 933 \end{split} 934 \end{equation} 975 \[ 976 % \label{eq:zdfbfr_linbfr_b} 977 \begin{split} 978 c_b^u &= - r\\ 979 c_b^v &= - r\\ 980 \end{split} 981 \] 935 982 When \np{nn\_botfr}\forcode{ = 1}, the value of $r$ used is \np{rn\_bfri1}. 936 983 Setting \np{nn\_botfr}\forcode{ = 0} is equivalent to setting $r=0$ and … … 950 997 951 998 The non-linear bottom friction parameterisation assumes that the bottom friction is quadratic: 952 \begin{equation} \label{eq:zdfbfr_nonlinear} 953 {\cal F}_h^\textbf{U} = \frac{A^{vm}}{e_3 }\frac{\partial \textbf {U}_h 954 }{\partial k}=C_D \;\sqrt {u_b ^2+v_b ^2+e_b } \;\; \textbf {U}_h^b 955 \end{equation} 999 \[ 1000 % \label{eq:zdfbfr_nonlinear} 1001 {\cal F}_h^\textbf{U} = \frac{A^{vm}}{e_3 }\frac{\partial \textbf {U}_h 1002 }{\partial k}=C_D \;\sqrt {u_b ^2+v_b ^2+e_b } \;\; \textbf {U}_h^b 1003 \] 956 1004 where $C_D$ is a drag coefficient, and $e_b $ a bottom turbulent kinetic energy due to tides, 957 1005 internal waves breaking and other short time scale currents. … … 965 1013 the bottom friction to the general momentum trend in \mdl{dynbfr}. 966 1014 For the non-linear friction case the terms computed in \mdl{zdfbfr} are: 967 \begin{equation} \label{eq:zdfbfr_nonlinbfr} 968 \begin{split} 969 c_b^u &= - \; C_D\;\left[ u^2 + \left(\bar{\bar{v}}^{i+1,j}\right)^2 + e_b \right]^{1/2}\\ 970 c_b^v &= - \; C_D\;\left[ \left(\bar{\bar{u}}^{i,j+1}\right)^2 + v^2 + e_b \right]^{1/2}\\ 971 \end{split} 972 \end{equation} 1015 \[ 1016 % \label{eq:zdfbfr_nonlinbfr} 1017 \begin{split} 1018 c_b^u &= - \; C_D\;\left[ u^2 + \left(\bar{\bar{v}}^{i+1,j}\right)^2 + e_b \right]^{1/2}\\ 1019 c_b^v &= - \; C_D\;\left[ \left(\bar{\bar{u}}^{i,j+1}\right)^2 + v^2 + e_b \right]^{1/2}\\ 1020 \end{split} 1021 \] 973 1022 974 1023 The coefficients that control the strength of the non-linear bottom friction are initialised as namelist parameters: … … 991 1040 If \np{ln\_loglayer} = .true., $C_D$ is no longer constant but is related to the thickness of 992 1041 the last wet layer in each column by: 993 \ begin{equation}994 C_D = \left ( {\kappa \over {\rm log}\left ( 0.5e_{3t}/rn\_bfrz0 \right ) } \right )^2995 \ end{equation}1042 \[ 1043 C_D = \left ( {\kappa \over {\rm log}\left ( 0.5e_{3t}/rn\_bfrz0 \right ) } \right )^2 1044 \] 996 1045 997 1046 \noindent where $\kappa$ is the von-Karman constant and \np{rn\_bfrz0} is a roughness length provided via … … 1001 1050 the base \np{rn\_bfri2} value and it is not allowed to exceed the value of an additional namelist parameter: 1002 1051 \np{rn\_bfri2\_max}, i.e.: 1003 \ begin{equation}1004 rn\_bfri2 \leq C_D \leq rn\_bfri2\_max1005 \ end{equation}1052 \[ 1053 rn\_bfri2 \leq C_D \leq rn\_bfri2\_max 1054 \] 1006 1055 1007 1056 \noindent Note also that a log-layer enhancement can also be applied to the top boundary friction if … … 1018 1067 bottom friction does not induce numerical instability. 1019 1068 For the purposes of stability analysis, an approximation to \autoref{eq:zdfbfr_flux2} is: 1020 \begin{equation} \label{eq:Eqn_bfrstab} 1021 \begin{split} 1022 \Delta u &= -\frac{{{\cal F}_h}^u}{e_{3u}}\;2 \rdt \\ 1023 &= -\frac{ru}{e_{3u}}\;2\rdt\\ 1024 \end{split} 1069 \begin{equation} 1070 \label{eq:Eqn_bfrstab} 1071 \begin{split} 1072 \Delta u &= -\frac{{{\cal F}_h}^u}{e_{3u}}\;2 \rdt \\ 1073 &= -\frac{ru}{e_{3u}}\;2\rdt\\ 1074 \end{split} 1025 1075 \end{equation} 1026 1076 \noindent where linear bottom friction and a leapfrog timestep have been assumed. 1027 1077 To ensure that the bottom friction cannot reverse the direction of flow it is necessary to have: 1028 \ begin{equation}1029 |\Delta u| < \;|u|1030 \ end{equation}1078 \[ 1079 |\Delta u| < \;|u| 1080 \] 1031 1081 \noindent which, using \autoref{eq:Eqn_bfrstab}, gives: 1032 \ begin{equation}1033 r\frac{2\rdt}{e_{3u}} < 1 \qquad \Rightarrow \qquad r < \frac{e_{3u}}{2\rdt}\\1034 \ end{equation}1082 \[ 1083 r\frac{2\rdt}{e_{3u}} < 1 \qquad \Rightarrow \qquad r < \frac{e_{3u}}{2\rdt}\\ 1084 \] 1035 1085 This same inequality can also be derived in the non-linear bottom friction case if 1036 1086 a velocity of 1 m.s$^{-1}$ is assumed. 1037 1087 Alternatively, this criterion can be rearranged to suggest a minimum bottom box thickness to ensure stability: 1038 \ begin{equation}1039 e_{3u} > 2\;r\;\rdt1040 \ end{equation}1088 \[ 1089 e_{3u} > 2\;r\;\rdt 1090 \] 1041 1091 \noindent which it may be necessary to impose if partial steps are being used. 1042 1092 For example, if $|u| = 1$ m.s$^{-1}$, $rdt = 1800$ s, $r = 10^{-3}$ then $e_{3u}$ should be greater than 3.6 m. … … 1070 1120 the bottom boundary condition is implemented implicitly. 1071 1121 1072 \begin{equation} \label{eq:dynzdf_bfr} 1073 \left.{\left( {\frac{A^{vm} }{e_3 }\ \frac{\partial \textbf{U}_h}{\partial k}} \right)} \right|_{mbk} 1074 = \binom{c_{b}^{u}u^{n+1}_{mbk}}{c_{b}^{v}v^{n+1}_{mbk}} 1075 \end{equation} 1122 \[ 1123 % \label{eq:dynzdf_bfr} 1124 \left.{\left( {\frac{A^{vm} }{e_3 }\ \frac{\partial \textbf{U}_h}{\partial k}} \right)} \right|_{mbk} 1125 = \binom{c_{b}^{u}u^{n+1}_{mbk}}{c_{b}^{v}v^{n+1}_{mbk}} 1126 \] 1076 1127 1077 1128 where $mbk$ is the layer number of the bottom wet layer. … … 1089 1140 The implementation of the implicit bottom friction in \mdl{dynspg\_ts} is done in two steps as the following: 1090 1141 1091 \begin{equation} \label{eq:dynspg_ts_bfr1} 1092 \frac{\textbf{U}_{med}-\textbf{U}^{m-1}}{2\Delta t}=-g\nabla\eta-f\textbf{k}\times\textbf{U}^{m}+c_{b} 1093 \left(\textbf{U}_{med}-\textbf{U}^{m-1}\right) 1094 \end{equation} 1095 \begin{equation} \label{eq:dynspg_ts_bfr2} 1096 \frac{\textbf{U}^{m+1}-\textbf{U}_{med}}{2\Delta t}=\textbf{T}+ 1097 \left(g\nabla\eta^{'}+f\textbf{k}\times\textbf{U}^{'}\right)- 1098 2\Delta t_{bc}c_{b}\left(g\nabla\eta^{'}+f\textbf{k}\times\textbf{u}_{b}\right) 1099 \end{equation} 1142 \[ 1143 % \label{eq:dynspg_ts_bfr1} 1144 \frac{\textbf{U}_{med}-\textbf{U}^{m-1}}{2\Delta t}=-g\nabla\eta-f\textbf{k}\times\textbf{U}^{m}+c_{b} 1145 \left(\textbf{U}_{med}-\textbf{U}^{m-1}\right) 1146 \] 1147 \[ 1148 \frac{\textbf{U}^{m+1}-\textbf{U}_{med}}{2\Delta t}=\textbf{T}+ 1149 \left(g\nabla\eta^{'}+f\textbf{k}\times\textbf{U}^{'}\right)- 1150 2\Delta t_{bc}c_{b}\left(g\nabla\eta^{'}+f\textbf{k}\times\textbf{u}_{b}\right) 1151 \] 1100 1152 1101 1153 where $\textbf{T}$ is the vertical integrated 3-D momentum trend. … … 1106 1158 the 3-D baroclinic mode. 1107 1159 $\textbf{u}_{b}$ is the bottom layer horizontal velocity. 1108 1109 1110 1111 1160 1112 1161 % ------------------------------------------------------------------------------------------------------------- … … 1157 1206 1158 1207 Otherwise, the implicit formulation takes the form: 1159 \begin{equation} \label{eq:zdfbfr_implicitts} 1160 \bar{U}^{t+ \rdt} = \; \left [ \bar{U}^{t-\rdt}\; + 2 \rdt\;RHS \right ] / \left [ 1 - 2 \rdt \;c_b^{u} / H_e \right ] 1161 \end{equation} 1208 \[ 1209 % \label{eq:zdfbfr_implicitts} 1210 \bar{U}^{t+ \rdt} = \; \left [ \bar{U}^{t-\rdt}\; + 2 \rdt\;RHS \right ] / \left [ 1 - 2 \rdt \;c_b^{u} / H_e \right ] 1211 \] 1162 1212 where $\bar U$ is the barotropic velocity, $H_e$ is the full depth (including sea surface height), 1163 1213 $c_b^u$ is the bottom friction coefficient as calculated in \rou{zdf\_bfr} and 1164 1214 $RHS$ represents all the components to the vertically integrated momentum trend except for 1165 1215 that due to bottom friction. 1166 1167 1168 1169 1216 1170 1217 % ================================================================ … … 1192 1239 $A^{vT}_{tides}$ is expressed as a function of $E(x,y)$, 1193 1240 the energy transfer from barotropic tides to baroclinic tides: 1194 \begin{equation} \label{eq:Ktides} 1195 A^{vT}_{tides} = q \,\Gamma \,\frac{ E(x,y) \, F(z) }{ \rho \, N^2 } 1241 \begin{equation} 1242 \label{eq:Ktides} 1243 A^{vT}_{tides} = q \,\Gamma \,\frac{ E(x,y) \, F(z) }{ \rho \, N^2 } 1196 1244 \end{equation} 1197 1245 where $\Gamma$ is the mixing efficiency, $N$ the Brunt-Vais\"{a}l\"{a} frequency (see \autoref{subsec:TRA_bn2}), … … 1209 1257 with a vertical scale of $h_o$ (\np{rn\_htmx} namelist parameter, 1210 1258 with a typical value of $500\,m$) \citep{St_Laurent_Nash_DSR04}, 1211 \begin{equation} \label{eq:Fz} 1212 F(i,j,k) = \frac{ e^{ -\frac{H+z}{h_o} } }{ h_o \left( 1- e^{ -\frac{H}{h_o} } \right) } 1213 \end{equation} 1259 \[ 1260 % \label{eq:Fz} 1261 F(i,j,k) = \frac{ e^{ -\frac{H+z}{h_o} } }{ h_o \left( 1- e^{ -\frac{H}{h_o} } \right) } 1262 \] 1214 1263 and is normalized so that vertical integral over the water column is unity. 1215 1264 … … 1234 1283 1235 1284 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 1236 \begin{figure}[!t] \begin{center} 1237 \includegraphics[width=0.90\textwidth]{Fig_ZDF_M2_K1_tmx} 1238 \caption{ \protect\label{fig:ZDF_M2_K1_tmx} 1239 (a) M2 and (b) K1 internal wave drag energy from \citet{Carrere_Lyard_GRL03} ($W/m^2$). } 1240 \end{center} \end{figure} 1285 \begin{figure}[!t] 1286 \begin{center} 1287 \includegraphics[width=0.90\textwidth]{Fig_ZDF_M2_K1_tmx} 1288 \caption{ 1289 \protect\label{fig:ZDF_M2_K1_tmx} 1290 (a) M2 and (b) K1 internal wave drag energy from \citet{Carrere_Lyard_GRL03} ($W/m^2$). 1291 } 1292 \end{center} 1293 \end{figure} 1241 1294 %>>>>>>>>>>>>>>>>>>>>>>>>>>>> 1242 1295 … … 1268 1321 the energy dissipation proportional to $N^2$ below the core of the thermocline and to $N$ above. 1269 1322 The resulting $F(z)$ is: 1270 \begin{equation} \label{eq:Fz_itf} 1271 F(i,j,k) \sim \left\{ \begin{aligned} 1272 \frac{q\,\Gamma E(i,j) } {\rho N \, \int N dz} \qquad \text{when $\partial_z N < 0$} \\ 1273 \frac{q\,\Gamma E(i,j) } {\rho \, \int N^2 dz} \qquad \text{when $\partial_z N > 0$} 1274 \end{aligned} \right. 1275 \end{equation} 1323 \[ 1324 % \label{eq:Fz_itf} 1325 F(i,j,k) \sim \left\{ 1326 \begin{aligned} 1327 \frac{q\,\Gamma E(i,j) } {\rho N \, \int N dz} \qquad \text{when $\partial_z N < 0$} \\ 1328 \frac{q\,\Gamma E(i,j) } {\rho \, \int N^2 dz} \qquad \text{when $\partial_z N > 0$} 1329 \end{aligned} 1330 \right. 1331 \] 1276 1332 1277 1333 Averaged over the ITF area, the resulting tidal mixing coefficient is $1.5\,cm^2/s$, … … 1283 1339 global coupled GCMs \citep{Koch-Larrouy_al_CD10}. 1284 1340 1285 1286 1341 % ================================================================ 1287 1342 % Internal wave-driven mixing … … 1299 1354 A three-dimensional field of internal wave energy dissipation $\epsilon(x,y,z)$ is first constructed, 1300 1355 and the resulting diffusivity is obtained as 1301 \begin{equation} \label{eq:Kwave} 1302 A^{vT}_{wave} = R_f \,\frac{ \epsilon }{ \rho \, N^2 } 1303 \end{equation} 1356 \[ 1357 % \label{eq:Kwave} 1358 A^{vT}_{wave} = R_f \,\frac{ \epsilon }{ \rho \, N^2 } 1359 \] 1304 1360 where $R_f$ is the mixing efficiency and $\epsilon$ is a specified three dimensional distribution of 1305 1361 the energy available for mixing. … … 1323 1379 (de Lavergne et al., in prep): 1324 1380 \begin{align*} 1325 F_{cri}(i,j,k) &\propto e^{-h_{ab} / h_{cri} }\\1326 F_{pyc}(i,j,k) &\propto N^{n\_p}\\1327 F_{bot}(i,j,k) &\propto N^2 \, e^{- h_{wkb} / h_{bot} }1381 F_{cri}(i,j,k) &\propto e^{-h_{ab} / h_{cri} }\\ 1382 F_{pyc}(i,j,k) &\propto N^{n\_p}\\ 1383 F_{bot}(i,j,k) &\propto N^2 \, e^{- h_{wkb} / h_{bot} } 1328 1384 \end{align*} 1329 1385 In the above formula, $h_{ab}$ denotes the height above bottom, 1330 1386 $h_{wkb}$ denotes the WKB-stretched height above bottom, defined by 1331 \ begin{equation*}1332 h_{wkb} = H \, \frac{ \int_{-H}^{z} N \, dz' } { \int_{-H}^{\eta} N \, dz' } \; ,1333 \ end{equation*}1387 \[ 1388 h_{wkb} = H \, \frac{ \int_{-H}^{z} N \, dz' } { \int_{-H}^{\eta} N \, dz' } \; , 1389 \] 1334 1390 The $n_p$ parameter (given by \np{nn\_zpyc} in \ngn{namzdf\_tmx\_new} namelist) 1335 1391 controls the stratification-dependence of the pycnocline-intensified dissipation. … … 1343 1399 % ================================================================ 1344 1400 1345 1401 \biblio 1346 1402 1347 1403 \end{document}
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