CSTMS UNSW2008

Adding Sediment to the Latte Example

On Friday, 3 April, there will be a tutorial for new ROMS users interested in sediments. This tutorial continues using the LATTE example presented during the Monday tutorial.

SWAN - A Digression

Getting SWAN set up correctly is easier if you do it separately. The coupling to ROMS is not seamless...you still have to specify the SWAN INPUT file, bathymetry, and some of the forcing for SWAN as separate files.

Directions in SWAN can be tricky. For our purposes, we will use these commands in the INPUT file:

SET NAUTICAL
COORDINATES SPHERICAL
CGRID CURVILINEAR 145 81 EXC 9.999000e+003 &
CIRCLE 36 0.0418 1.0 24
READGRID COORDINATES 1 './lattec_swan.grd' 4 0 0 FREE

NAUTICAL implies that directions are specified in degrees and (for wind and waves) indicate the direction from which the wind/waves are approaching, For example, a uniform southwesterly wind (blowing toward the northeast) at 5 m/s for a stationary run would be specified as

WIND 5 225

SWAN output in .mat files should be interpreted this way as well.

In the Latte example, we have good wind forcing files that work with ROMS, and we want to use the same files to force waves in SWAN. We will use the SWAN commands

INPGRID WIND CURVILINEAR 0 0 145 81 EXC 9.999000e+003 &
NONSTATIONARY 20060405.000000 1 HR 20060608.230000
READINP WIND 1 'swan_lattec_wind.dat' 4 0 FREE

The file swan_lattec_wind.dat has sequences of u and v velocities written for each time step. The u- and v- components are aligned with the x- and y-axes of the SWAN grid. The order in which they are written is determined by the 'layout' parameter (in this case, 4), which means the file looks like this.

u(1,1,1) u(1,1,2) ... u(1,1,nj)
u(1,2,1) u(1,2,2) ... u(1,2,nj)
...
u(1,ni,1) u(1,ni,2)... u(1,ni,nj)
v(1,1,1) v(1,1,2) ... v(1,1,nj)
v(1,2,1) v(1,2,2) ... v(1,2,nj)
...
v(1,ni,1) v(1,ni,2)... v(1,ni,nj)
u(1,1,1) u(1,1,2) ... u(1,1,nj)
u(1,2,1) u(1,2,2) ... u(1,2,nj)
...
u(1,ni,1) u(1,ni,2)... u(1,ni,nj)
v(2,1,1) v(2,1,2) ... v(2,1,nj)
v(2,2,1) v(2,2,2) ... v(2,2,nj)
...
v(2,ni,1) v(2,ni,2)... v(2,ni,nj)
...etc

where the first indice is time step (1...nt), the second is x-direction (1...ni) and the third is y-direction (1...nj).