Changeset 10614
 Timestamp:
 20190131T18:10:55+01:00 (3 years ago)
 Location:
 NEMO/trunk/doc/latex/NEMO
 Files:

 3 edited
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NEMO/trunk/doc/latex/NEMO/main/NEMO_manual.tex
r10585 r10614 50 50 Massimiliano Drudi, Christian Eth\'{e}, Simona Flavoni, Doroteaciro Iovino, Claire L\'{e}vy, Tomas Lovato, 51 51 Nicolas Martin, S\'{e}bastien Masson, Pierre Mathiot, Gelsomina Mattia, Francesca Mele, Silvia Mocavero, 52 George Nurser, Enda O'Dea, Julien Paul, Cl\'{e}ment Rousset, Dave Storkey, Martin Vancoppenolle 52 Simon M\"{u}ller, George Nurser, Enda O'Dea, Julien Paul, Cl\'{e}ment Rousset, Dave Storkey, 53 Martin Vancoppenolle 53 54 } \\ 54 55 \\ 
NEMO/trunk/doc/latex/NEMO/subfiles/chap_LBC.tex
r10530 r10614 711 711 % 712 712 713 Options are defined through the \ngn{nambdy\_tide} namelist variables 714 for reading in the complex harmonic amplitudes of elevation (ssh) and barotropic velocity (u,v). 715 716 The tidal harmonic data can be specified in 2 ways.\\ 717 First it can be specified on a 2D grid covering the entire model domain in which case the user should set \np{ln\_bdytide\_2ddta }\forcode{ = .true.}. 718 In this case the model assumes that the real and imaginary parts are split. 719 The variable naming convention is \textit{constituent\_name\_z1} for real SSH and \textit{constituent\_name\_z2} for imaginary SSH. 720 The available \textit{constituent\_names} in NEMO are defined in \rou{SBC/tide.h90} 721 Likewise for $u$ and $v$ data. File name is assumed to be \np{filtide}\ifile{\_grid\_T} for the elevation component 722 and \np{filtide}\ifile{\_grid\_U} for the u barotropic velocity and \np{filtide}\ifile{\_grid\_V} for the v barotropic velocity.\\ 723 Otherwise, the tidal data must be specified along bdy segments. 724 In this case each constituent has its own file name and the real part is assumed to be z1 and the imaginary part z2 for SSH. 725 Similarly u1, u2 and v1, v2 for velocities. Input file name convention (for elevation of the M2 tidal component) is \np{filtide}\ifile{M2\_grid\_T}. 726 Similar logic applies for other components and u and v barotropic velocities.\\ 727 728 The data may also be in complex conjugate form. If that is the case then the user should set \np{ln\_bdytide\_conj}\forcode{ = .true. } 729 so the model correctly interprets the data. The default case assumes it is not in complex conjugate form. 730 731 Note the barotropic velocities are assumed to be on the model native grid and must be rotated as appropriate from the source grid upon which they are extracted from. 732 To do so convert to U, V amplitude and phase into tidal ellipses. Add the grid rotation to ellipse inclination and convert back. Be careful about conventions 733 of direction of rotation, e.g. anticlockwise or clockwise. 713 Tidal forcing at open boundaries requires the activation of surface 714 tides (i.e., in \ngn{nam\_tide}, \np{ln\_tide} needs to be set to 715 \forcode{.true.} and the required constituents need to be activated by 716 including their names in the \np{cname} array; see 717 \autoref{sec:SBC_tide}). Specific options related to the reading in of 718 the complex harmonic amplitudes of elevation (SSH) and barotropic 719 velocity (u,v) at open boundaries are defined through the 720 \ngn{nambdy\_tide} namelist parameters.\\ 721 722 The tidal harmonic data at open boundaries can be specified in two 723 different ways, either on a twodimensional grid covering the entire 724 model domain or along open boundary segments; these two variants can 725 be selected by setting \np{ln\_bdytide\_2ddta } to \forcode{.true.} or 726 \forcode{.false.}, respectively. In either case, the real and 727 imaginary parts of SSH and the two barotropic velocity components for 728 each activated tidal constituent \textit{tcname} have to be provided 729 separately: when twodimensional data is used, variables 730 \textit{tcname\_z1} and \textit{tcname\_z2} for real and imaginary SSH, 731 respectively, are expected in input file \np{filtide} with suffix 732 \ifile{\_grid\_T}, variables \textit{tcname\_u1} and 733 \textit{tcname\_u2} for real and imaginary u, respectively, are 734 expected in input file \np{filtide} with suffix \ifile{\_grid\_U}, and 735 \textit{tcname\_v1} and \textit{tcname\_v2} for real and imaginary v, 736 respectively, are expected in input file \np{filtide} with suffix 737 \ifile{\_grid\_V}; when data along open boundary segments is used, 738 variables \textit{z1} and \textit{z2} (real and imaginary part of SSH) 739 are expected to be available from file \np{filtide} with suffix 740 \ifile{tcname\_grid\_T}, variables \textit{u1} and \textit{u2} (real 741 and imaginary part of u) are expected to be available from file 742 \np{filtide} with suffix \ifile{tcname\_grid\_U}, and variables 743 \textit{v1} and \textit{v2} (real and imaginary part of v) are 744 expected to be available from file \np{filtide} with suffix 745 \ifile{tcname\_grid\_V}. If \np{ln\_bdytide\_conj} is set to 746 \forcode{.true.}, the data is expected to be in complex conjugate 747 form. 748 749 Note that the barotropic velocity components are assumed to be defined 750 on the native model grid and should be rotated accordingly when they 751 are converted from their definition on a different source grid. To do 752 so, the u, v amplitudes and phases can be converted into tidal 753 ellipses, the grid rotation added to the ellipse inclination, and then 754 converted back (care should be taken regarding conventions of the 755 direction of rotation). %, e.g. anticlockwise or clockwise. 734 756 735 757 \biblio 
NEMO/trunk/doc/latex/NEMO/subfiles/chap_SBC.tex
r10468 r10614 815 815 816 816 The tidal forcing, generated by the gravity forces of the EarthMoon and EarthSun sytems, 817 is activated if \np{ln\_tide} and \np{ln\_tide\_pot} are both set to \ np{.true.} in \ngn{nam\_tide}.817 is activated if \np{ln\_tide} and \np{ln\_tide\_pot} are both set to \forcode{.true.} in \ngn{nam\_tide}. 818 818 This translates as an additional barotropic force in the momentum equations \ref{eq:PE_dyn} such that: 819 819 \[ … … 822 822 +g\nabla (\Pi_{eq} + \Pi_{sal}) 823 823 \] 824 where $\Pi_{eq}$ stands for the equilibrium tidal forcing and $\Pi_{sal}$ a selfattraction and loading term (SAL). 824 where $\Pi_{eq}$ stands for the equilibrium tidal forcing and 825 $\Pi_{sal}$ is a selfattraction and loading term (SAL). 825 826 826 The equilibrium tidal forcing is expressed as a sum over the chosen constituents $l$ in \ngn{nam\_tide}. 827 The constituents are defined such that \np{clname(1) = 'M2', clname(2)='S2', etc...}. 828 For the three types of tidal frequencies it reads: \\ 829 Long period tides : 830 \[ 831 \Pi_{eq}(l)=A_{l}(1+kh)(\frac{1}{2}\frac{3}{2}sin^{2}\phi)cos(\omega_{l}t+V_{l}) 832 \] 833 diurnal tides : 834 \[ 835 \Pi_{eq}(l)=A_{l}(1+kh)(sin 2\phi)cos(\omega_{l}t+\lambda+V_{l}) 836 \] 837 Semidiurnal tides: 838 \[ 839 \Pi_{eq}(l)=A_{l}(1+kh)(cos^{2}\phi)cos(\omega_{l}t+2\lambda+V_{l}) 840 \] 841 Here $A_{l}$ is the amplitude, $\omega_{l}$ is the frequency, $\phi$ the latitude, $\lambda$ the longitude, 842 $V_{0l}$ a phase shift with respect to Greenwich meridian and $t$ the time. 843 The Love number factor $(1+kh)$ is here taken as a constant (0.7). 844 845 The SAL term should in principle be computed online as it depends on the model tidal prediction itself 846 (see \citet{Arbic2004} for a discussion about the practical implementation of this term). 847 Nevertheless, the complex calculations involved would make this computationally too expensive. 848 Here, practical solutions are whether to read complex estimates $\Pi_{sal}(l)$ from an external model 849 (\np{ln\_read\_load=.true.}) or use a ``scalar approximation'' (\np{ln\_scal\_load=.true.}). 850 In the latter case, it reads:\\ 851 \[ 852 \Pi_{sal} = \beta \eta 853 \] 854 where $\beta$ (\np{rn\_scal\_load}, $\approx0.09$) is a spatially constant scalar, 855 often chosen to minimize tidal prediction errors. 856 Setting both \np{ln\_read\_load} and \np{ln\_scal\_load} to false removes the SAL contribution. 827 The equilibrium tidal forcing is expressed as a sum over a subset of 828 constituents chosen from the set of available tidal constituents 829 defined in file \rou{SBC/tide.h90} (this comprises the tidal 830 constituents \textit{M2, N2, 2N2, S2, K2, K1, O1, Q1, P1, M4, Mf, Mm, 831 Msqm, Mtm, S1, MU2, NU2, L2}, and \textit{T2}). Individual 832 constituents are selected by including their names in the array 833 \np{clname} in \ngn{nam\_tide} (e.g., \np{clname(1) = 'M2', 834 clname(2)='S2'} to select solely the tidal consituents \textit{M2} 835 and \textit{S2}). Optionally, when \np{ln\_tide\_ramp} is set to 836 \forcode{.true.}, the equilibrium tidal forcing can be ramped up 837 linearly from zero during the initial \np{rdttideramp} days of the 838 model run. 839 840 The SAL term should in principle be computed online as it depends on 841 the model tidal prediction itself (see \citet{Arbic2004} for a 842 discussion about the practical implementation of this term). 843 Nevertheless, the complex calculations involved would make this 844 computationally too expensive. Here, two options are available: 845 $\Pi_{sal}$ generated by an external model can be read in 846 (\np{ln\_read\_load=.true.}), or a ``scalar approximation'' can be 847 used (\np{ln\_scal\_load=.true.}). In the latter case 848 \[ 849 \Pi_{sal} = \beta \eta, 850 \] 851 where $\beta$ (\np{rn\_scal\_load} with a default value of 0.094) is a 852 spatially constant scalar, often chosen to minimize tidal prediction 853 errors. Setting both \np{ln\_read\_load} and \np{ln\_scal\_load} to 854 \forcode{.false.} removes the SAL contribution. 857 855 858 856 % ================================================================
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