13.3. Coupled variables¶
13.3.1. Coupling with an atmospheric model¶
When coupling CROCO to an atmospheric model, to have a consistent interface, you should use momentum and heat fluxes computed from the atmospheric model bulk formula.
No surface forcing file is required (only boundary forcing, and eventually tidal forcing).
The following cpp-keys have to be set:
# define OA_COUPLING
# define MPI
# undef BULK_FLUX
# undef SMFLUX_CFB
Note
SMFLUX_CFB is a cpp-key to use a wind stress relative to the current in forced mode. In coupled mode, as current is sent to the atmosphere, the wind stress from the atmospheric model account for such a current feedback.
Fields sent by CROCO |
||
|---|---|---|
Name (units) |
name and eventual oper. in the model |
OASIS name |
SST (K) |
t(:,:,N,nnew,itemp) + 273.15 |
CROCO_SST |
U-component of current (m/s) |
u (at rho points):
0.5*(u(1:Lmmpi,1:Mmmpi,N,nnew)
+u(2:Lmmpi+1,1:Mmmpi,N,nnew))
|
CROCO_UOCE |
V-component of current (m/s) |
v (at rho points):
0.5*(v(1:Lmmpi,1:Mmmpi,N,nnew)
+v(1:Lmmpi,2:Mmmpi+1,N,nnew))
|
CROCO_VOCE |
Eastward component of current (m/s) |
u (at rho points) rotated eastwards
(useful for rotated grids)
(0.5 * (u(1:Lmmpi ,1:Mmmpi,N,nnew)
+ u(2:Lmmpi+1,1:Mmmpi,N,nnew)) )
* cos(angler(1:Lmmpi ,1:Mmmpi))
- (0.5 * (v(1:Lmmpi,1:Mmmpi ,N,nnew)
+ v(1:Lmmpi,2:Mmmpi+1,N,nnew)) )
* sin(angler(1:Lmmpi ,1:Mmmpi))
+u(2:Lmmpi+1,1:Mmmpi,N,nnew))
|
CROCO_EOCE |
Northward component of current (m/s) |
v (at rho points) rotated northward
(useful for rotated grids)
(0.5 * (u(1:Lmmpi ,1:Mmmpi,N,nnew)
+ u(2:Lmmpi+1,1:Mmmpi,N,nnew)) )
* sin(angler(1:Lmmpi ,1:Mmmpi))
+ (0.5 * (v(1:Lmmpi,1:Mmmpi ,N,nnew)
+ v(1:Lmmpi,2:Mmmpi+1,N,nnew)) )
* cos(angler(1:Lmmpi ,1:Mmmpi))
|
CROCO_NOCE |
Fields received by CROCO |
||
|---|---|---|
Name (units) |
name and eventual oper. in the model |
OASIS name |
U component of wind stress (N/m2) |
sustr (at u point):
0.5*(FIELD(io-1,jo)+FIELD(io,jo))/rho0
if eastward, it is first rotated:
FIELD = etau * cos(angler)
+ ntau * sin(angler)
|
CROCO_UTAW or CROCO_ETAW |
V component of wind stress (N/m2) |
svstr (at v point):
0.5*(FIELD(io,jo-1)+FIELD(io,jo))/rho
if northward, it is first rotated:
FIELD = ntau * cos(angler)
- etau * sin(angler)
|
CROCO_VTAW or CROCO_NTAW |
Wind stress module (N/m2) |
smstr = FIELD / rho0 |
CROCO_TAUM |
Surface net solar flux (W/m2) |
srflx = FIELD / (rho0*Cp) |
CROCO_SRFL |
Surface net non-solar flux (W/m2) |
stflx(:,:,itemp) = FIELD / (rho0*Cp) |
CROCO_STFL |
Evaporation-Precipitation (kg/m2/s) |
stflx(:,:,isalt) = FIELD / 1000 |
CROCO_EVPR |
Surface atmospheric pressure (Pa) |
patm2d = FIELD |
CROCO_PSFC |
Fields received by WRF |
||
|---|---|---|
Name (units) |
name (in the model) |
OASIS name |
SST (K) |
SST |
WRF_d01_EXT_d01_SST |
U component of current (m/s) |
UOCE |
WRF_d01_EXT_d01_UOCE |
V component of current (m/s) |
VOCE |
WRF_d01_EXT_d01_VOCE |
Eastward component of current (m/s) |
EOCE |
WRF_d01_EXT_d01_EOCE |
Northward component of current (m/s) |
NOCE |
WRF_d01_EXT_d01_NOCE |
Fields sent by WRF |
||
|---|---|---|
Name (units) |
name (in the model) |
OASIS name |
Surface net solar flux (W/m2) |
GSW |
WRF_d01_EXT_d01_SURF_NET_SOLAR |
Surface net non-solar flux (W/m2) |
GLW-STBOLT*EMISS*SST**4-LH-HFX |
WRF_d01_EXT_d01_SURF_NET_NON-SOLAR |
Evaporation-precipitation (kg/m2/s) |
QFX-(RAINCV+RAINNCV)/DT |
WRF_d01_EXT_d01_EVAP-PRECIP |
Surface atmospheric pressure (Pa) |
PSFC |
WRF_d01_EXT_d01_PSFC |
Wind stress module (N/m2) |
taut = rho * ust**2 |
WRF_d01_EXT_d01_TAUMOD |
U component of wind stress (N/m2) |
taui = taut * u_uo / wspd |
WRF_d01_EXT_d01_TAUX |
V component of wind stress (N/m2) |
tauj = taut * v_uo / wspd |
WRF_d01_EXT_d01_TAUY |
Eastward comp. of wind stress(N/m2) |
cosa * taui - sina * tauj |
WRF_d01_EXT_d01_TAUE |
Northward comp. of wind stress(N/m2) |
cosa * tauj + sina * taui |
WRF_d01_EXT_d01_TAUN |
Note
If you decide to couple CROCO with multiple WRF domains, variables coming from WRF will be defined by adding _EXT*. Here * corresponds to which domains the variable is coming (1=Parent, 2=Nest 1 ,…).
13.3.2. Coupling with a wave model¶
When coupling CROCO to a wave model, the wave-current interactions have to be set on. At the moment, only mean wave parameters are exchanged, their contribution to ocean dynamics is computed into the wave-current interaction routine in CROCO.
The following cpp-keys have to be set:
# define OW_COUPLING
# define MPI
# define MRL_WCI
Note
You also have to be careful to the choice of the momentum flux. For better consistency, here we suggest to account for the momentum flux seen by the wave model, and thus set:
# undef BULK_FLUX
# define WAVE_SMFLUX
Fields sent by CROCO |
||
|---|---|---|
Name (units) |
name and eventual oper. in the model |
OASIS name |
SSH (m) |
zeta |
CROCO_SSH |
U-component of current (m/s) |
u (at rho points):
0.5*(u(1:Lmmpi,1:Mmmpi,N,nnew)
+u(2:Lmmpi+1,1:Mmmpi,N,nnew))
|
CROCO_UOCE |
V-component of current (m/s) |
v (at rho points):
0.5*(v(1:Lmmpi,1:Mmmpi,N,nnew)
+v(1:Lmmpi,2:Mmmpi+1,N,nnew))
|
CROCO_VOCE |
Eastward component of current (m/s) |
u (at rho points) rotated to east
(useful for rotated grids)
(0.5 * (u(1:Lmmpi ,1:Mmmpi,N,nnew)
+ u(2:Lmmpi+1,1:Mmmpi,N,nnew)) )
* cos(angler(1:Lmmpi ,1:Mmmpi))
- (0.5 * (v(1:Lmmpi,1:Mmmpi ,N,nnew)
+ v(1:Lmmpi,2:Mmmpi+1,N,nnew)) )
* sin(angler(1:Lmmpi ,1:Mmmpi))
+u(2:Lmmpi+1,1:Mmmpi,N,nnew))
|
CROCO_EOCE |
Northward component of current (m/s) |
v (at rho points) rotated to north
(useful for rotated grids)
(0.5 * (u(1:Lmmpi ,1:Mmmpi,N,nnew)
+ u(2:Lmmpi+1,1:Mmmpi,N,nnew)) )
* sin(angler(1:Lmmpi ,1:Mmmpi))
+ (0.5 * (v(1:Lmmpi,1:Mmmpi ,N,nnew)
+ v(1:Lmmpi,2:Mmmpi+1,N,nnew)) )
* cos(angler(1:Lmmpi ,1:Mmmpi))
|
CROCO_NOCE |
Fields received by CROCO |
||
|---|---|---|
Name (units) |
name and eventual oper. in the model |
OASIS name |
Significant wave height (m) |
whrm = FIELD * 0.70710678 |
CROCO_HS |
Mean wave period (s) -> frequency |
wfrq = 2*pi / FIELD |
CROCO_T0M1 |
Mean wave direction -> wavenumbers |
wdrx = cos(FIELD - angler)
wdre = sin(FIELD - angler)
|
CROCO_DIR |
U component of wave stress (m2/s2) |
twox (at u point):
0.5*(FIELD(io-1,jo)+FIELD(io,jo))
if eastward, it is first rotated:
FIELD = etwo * cos(angler)
+ ntwo * sin(angler)
|
CROCO_UTWO or CROCO_ETWO |
V component of wave stress (m2/s2) |
twoy (at v point):
0.5*(FIELD(io,jo-1)+FIELD(io,jo))
if northward, it is first rotated:
FIELD = ntwo * cos(angler)
- etwo * sin(angler)
|
CROCO_VTWO or CROCO_NTWO |
U comp. of wind-to-wave stress (m2/s2) |
tawx (at u point):
0.5*(FIELD(io-1,jo)+FIELD(io,jo))
if eastward, it is first rotated:
FIELD = etaw * cos(angler)
+ ntaw * sin(angler)
|
CROCO_UTAW or CROCO_ETAW |
V comp. of wind-to-wave stress (m2/s2) |
tawy (at v point):
0.5*(FIELD(io,jo-1)+FIELD(io,jo))
if northward, it is first rotated:
FIELD = ntaw * cos(angler)
- etaw * sin(angler)
|
CROCO_VTAW or CROCO_NTAW |
Other optional fields enventually sent, if not, they are analytically computed in the MRL_WCI routine |
||
Bernoulli head pressure (N/m) |
bhd |
CROCO_BHD |
Wave-to-ocean TKE flux (W/m2) |
foc |
CROCO_FOC |
Mean wavelength (m) |
wlm |
CROCO_LM |
Wave orbital bottom velocity (m/s) |
ubr = sqrt(ubrx**2+ubry**2) |
CROCO_UBRX and CROCO_UBRY |
Stokes drift surface velocity (m/s) |
ust_ext = sqrt(ustx_ext**2+usty_ext**2) |
CROCO_USSX and CROCO_USSY |
Fields received by WW3 |
||
|---|---|---|
Name (units) |
name (in the model) |
OASIS name |
SSH = water level (m) |
LEV |
WW3__SSH |
Zonal current (m/s) |
CUR |
WW3_OSSU |
Meridional current (m/s) |
CUR |
WW3_OSSV |
Fields sent by WW3 |
||
|---|---|---|
Name (units) |
name (in the model) |
OASIS name |
Mean wave period (s) |
T0M1 |
WW3_T0M1 |
Significant wave height (m) |
HS |
WW3__OHS |
Mean wave direction |
THM |
WW3__DIR |
Zonal wave stress (N/m2) |
TWOX |
WW3_TWOX |
Meridional wave stress (N/m2) |
TWOY |
WW3_TWOY |
Zonal wind stress (N/m2) |
TAWX |
WW3_TAWX |
Meridional wind stress(N/m2) TAWY WW3_TAWY |
||
Other fields possibly sent, but not used in coupling with CROCO at the moment |
||
Bernoulli head pressure (N/m) |
BHD |
WW3__BHD |
Bottom orbital velocity (m/s) |
UBR |
WW3__UBR |
Wave-to-ocean TKE flux (W/m2) |
FOC |
WW3__FOC |
Mean wavelength (m) |
LM |
WW3___LM |
Wave peak frequency (/s) |
FP |
WW3___FP |
13.3.3. Coupling atmosphere and wave models¶
Fields received by WW3 |
||
|---|---|---|
Name (units) |
name (in the model) |
OASIS name |
Zonal wind (m/s) |
WND |
WW3__U10 |
Meridional wind (m/s) |
WND |
WW3__V10 |
Fields sent by WW3 |
||
|---|---|---|
Name (units) |
name (in the model) |
OASIS name |
Significant wave height (m) |
HS |
WW3__AHS |
Charnock coefficient |
ACHA |
WW3_ACHA |
Fields sent by WRF |
||
|---|---|---|
Name (units) |
name (in the model) |
OASIS name |
Zonal wind at first level( (m/s) |
u_uo |
WRF_d01_EXT_d01_WND_E_01 |
Meridional wind at first level (m/s) |
v_vo |
WRF_d01_EXT_d01_WND_N_01 |
Fields received by WRF |
||
|---|---|---|
Name (units) |
name (in the model) |
OASIS name |
Charnock coefficient |
CHA_COEF |
WRF_d01_EXT_d01_CHA_COEF |
13.3.4. Note on momentum flux when coupling 3 models¶
As the wave model has a quite complex parameterization of wave generation by winds, which is in subtle balance with the wave dissipation, the wind stress for the wave model is computed by its own parameterization. Therefore, to ensure energetic consistency of the momentum flux when coupling 3 models, we prescribe the wind stress in CROCO as:
sustr = sustr_from_atm_model - tawx + twox
svstr = svstr_from_atm_model - tawy + twoy
# where taw is stress from atm to waves
# and two is stress from waves to ocean
13.3.5. Note on coupling with AGRIF¶
You may decide to coupled CROCO while using AGRIF. To do so, the variables sent by the parent domain (0) and the child domains (1,2,…) must be separated. Thus the variables sent, in case of using AGRIF, take the radical defined above (CROCO_VAR) to which we add _0 (for parent) or _1 (for first child). This gives, for example for variable SST, CROCO_SST_0 or CROCO_SST_1 for parent and child respectively.
For the variables received by CROCO, we will use its ability to handle CPLMASK. Each of the domains (parent or children) will be assigned a coupling mask named coupling_mask0.nc (parent), coupling_mask1.nc (child 1), each coupling mask being relative to its grid. The CROCO domain that receives a variable will be identified by its mask (CPLMASK*), which will be added to the previous radical. This will give CROCO_VAR_CPLMASK0 for the parent or CROCO_VAR_CPLMASK1 for child 1.
This makes it easy to define the received variables in a case where one decides to couple CROCO-AGRIF with several WRF domains. In this case the variables will have the nomenclature CROCO_VAR_CPLMASK0 for the parent CROCO to which we add _EXT1 for the first domain of coupling_mask0.nc. By continuity _EXT2 will correspond to domain 2 of coupling_mask0.nc. Then the variables received by CROCO, in a case of CROCO-AGRIF/WRF-nest simulation, will follow the format CROCO_VAR_CPLMASK*_EXT*.