# Ariane¶

Ariane is a Fortran code used to compute 3D streamlines in a given velocity field.

## Getting the code¶

The primary location to get the code is via the .. _Ariane website: http://stockage.univ-brest.fr/~grima/Ariane/download.php

You can get modifications that we’ve made to the source files for our usage here (we’re working with version 2.2.8_04): .. code-block:: bash

cd /ocean/$USER/$PROJECT/ hg clone ssh://hg@bitbucket.org/eliseolsen/arianesrc-2.2.8_04

## Installing on salish¶

Specify the locations of the netcdf libraries to help the configure script find them:

    cd /ocean/$USER/$PROJECT/ariane-2.2.8_04/
export NETCDF_INC=/usr/include
export NETCDF_LIB=/usr/lib


cd /ocean/$USER/$PROJECT/ariane-2.2.8_04
./configure --prefix=/ocean/$USER/$PROJECT/ariane-2.2.8_04


The prefix argument overwrites the default install directory into a customized directory.

Make and install Ariane (you will need to do this every time you make changes to the code):

cd /ocean/$USER/$PROJECT/ariane-2.2.8_04
make
make check
make install


make compiles source files, make check tests Ariane’s qualitative and quantitative modes, and make install installs Ariane.

Add the path for the Ariane executable to your PATH environment variable:

export PATH=/ocean/$USER/$PROJECT/ariane-2.2.8_04/bin:$PATH  Now you can run Ariane from any directory by typing ariane. ## Testing Ariane¶ To test that you have everything set up correctly, run one of the Ariane examples. For instance, try:  cd /ocean/$USER/\$PROJECT/ariane-2.2.8_04/examples/qualitative
ariane


You should notice several new files, such as ariane_trajectories_qualitative.nc and traj.txt. These files contain the trajectory information.

• ariane_trajectories_qualitative.nc can be loaded into a notebook to plot the particle locations over time and starting/finishing points, etc.
• traj.txt is helpful if you want to get a general idea of what the resulting trajectory coordinates look like or to check if the simulation ran properly.

## Running Ariane: An example for Salish Sea model¶

To run your own trajectory simulation with Salish Sea model output, create a run directory. For example, on your local machine:

mkdir -p  /ocean/username/MEOPAR/Ariane/results/myexperiment


You will need namelist and initial_positions.txt files in this run directory (see below).

Type ariane to run the code.

### intitial_positions.txt¶

The initial_positions.txt file is where you will specify the initial positions and initial times of the particles you are tracking. It contains 5 columns and as many rows as there are particles in the simulation you are running.

310 360 1.0 0.5 1.0
310     370     1.5 0.5 1.0
310     380 2.0 1.5 1.0
310 410 1.0 0.5 1.0
331 415 1.0 0.5 1.0


This simulation, for example, will have 5 particles.

• Column 1: Spatial grid index (X)

• Column 2: Spatial grid index (Y)

• Column 3: Spatial grid index (Z)

• A negative value tells Ariane to confine the particle to its original depth throughout its trajectory. If you would like to have the particle trajectory include vertical movement, enter positive values and provide Ariane with the W velocity components in namelist if using NEMO data.
• Since Ariane starts counting from 1, a “1” or “-1” here means the first depth grid box. The NEMO output grid boxes are 1 metre in height for the first few metres. This means that the second particle in this example (whose Z index is -1.5) would have a trajectory identical to that of a particle with Z index -1 if they shared the same X, Y, and T indices.
• Column 4: Time index or fl

• Use “0.5” if you want to start at NEMO time 00:00. Use “1” if you want to start at NEMO time 00:30.
• Column 5: Fifth parameter = 1.0

Note

Ariane uses FORTAN indexing, which counts starting at 1. If you used Python to look up initial positions, which starts counting at 0, then you should add 1 to your initial positions.

### namelist¶

Note

Ariane can be run in 2 modes, quantitative and qualitative. This example, and therefore this version of the namelist, is qualitative.

An example Ariane namelist configured to a Salish Sea model run with hourly output over two days is provided below. This namelist is also under version control in analysis/Nancy/Ariane_namelists/namelist.

&ARIANE
key_alltracers =.FALSE.,
key_sequential =.FALSE.,
key_ascii_outputs =.TRUE.,
mode ='qualitative',
forback ='forward',
bin ='nobin',
init_final ='init',
nmax =5,
tunit =3600.,
ntfic =1,
tcyc =0.,
/

&OPAPARAM
imt =398,
jmt =898,
kmt =40,
lmt =48,
key_periodic =.FALSE.,
key_jfold =.FALSE.,
key_computew =.TRUE.,
key_partialsteps =.TRUE.,
/

&QUALITATIVE
delta_t =3600.,
frequency =1,
nb_output =46,
key_region =.FALSE.,
/

&ZONALCRT
c_dir_zo ='/data/nsoontie/MEOPAR/SalishSea/results/storm-surges/tide_fix/dec2006/all_forcing/1hour/',
c_prefix_zo ='SalishSea_1h_20061214_20061215_grid_U.nc',
ind0_zo =-1,
indn_zo =-1,
maxsize_zo =-1,
c_suffix_zo ='NONE',
nc_var_zo ='vozocrtx',
nc_var_eivu ='NONE',
/

&MERIDCRT
c_dir_me ='/data/nsoontie/MEOPAR/SalishSea/results/storm-surges/tide_fix/dec2006/all_forcing/1hour/',
c_prefix_me ='SalishSea_1h_20061214_20061215_grid_V.nc',
ind0_me =-1,
indn_me =-1,
maxsize_me =-1,
c_suffix_me ='NONE',
nc_var_me ='vomecrty',
nc_var_eivv ='NONE',
/

&MESH
dir_mesh ='/ocean/nsoontie/MEOPAR/Ariane/',
nc_var_xx_tt ='glamt',
nc_var_xx_uu ='glamu',
nc_var_yy_tt ='gphit',
nc_var_yy_vv ='gphiv',
nc_var_zz_ww ='gdepw',
nc_var_e2u ='e2u',
nc_var_e1v ='e1v',
nc_var_e1t ='e1t',
nc_var_e2t ='e2t',
nc_var_e3t ='e3t',
/


The general setup for the simulation is specified in the sections ARIANE, OPAPARAM, and QUALITATIVE. Some of the parameters are described in the table below. For a more detailed description of the parameters, please refer to the Ariane documentation: Ariane Namelist

Parameter Description Parameter Description
nmax Number of particles kmt Vertical space dimension (depth)
tunit

Unit of time.

Example: 3600 for 1 hour

lmt

Number of time steps

in input data

ntfic

x tunit = Time period covered

by each time sample in input files

delta_t

Unit of time.

Example: 3600 for 1 hour

imt

Horizontal space dimension

(longitude)

frequency

x delta_t = Time interval

between two sucessive position outputs

jmt

Horizontal space dimension

(latitude)

nb_output

Total number of position outputs for

each trajectory.

Note

Condition 1: delta_t × frequency × nb_output < tunit × ntfic × lmt

Condition 2: delta_t × frequency × nb_output < tunit × ntfic × (lmt + 0.5 - max(fl))

Condition 1 must be satisfied if the maximum time index is 0.5.
Condition 2 must also be satisfied if any inital time index fl is greater than 0.5.

We must also specify where Salish Sea model output is stored in sections ZONALCRT and MERIDCRT. You can also input the vertical velocity component (recommended if using NEMO data) under VERTICRT or Ariane can compute it using the horizontal components. There is also the option of specifying temperature, salinity, and density in the sections TEMPERAT, SALINITY, and DENSITY respectively.

Parameter Description
c_dir_zo, c_dir_me Directory where data is store
c_prefix_zo, c_prefix_me NetCDF file name with velocity data
nc_var_zo, nc_var_me Variable name for velocity component
dir_mesh Directory where grid is stored
fn_mesh NetCDF file name with grid

Namelists can be constructed using the namelist assistant on the Ariane website: Namelist Assistant

Finally, the MESH section indicates where information about the Salish Sea model grid is stored. A file, mesh_mask.nc, contains the mapping scale factors and grid masks needed by Ariane. This is a large file not under version control but can be found in /ocean/nsoontie/MEOPAR/Ariane.

## Ariane output¶

The trajectories can be plotted in a python notebook. Different colours are used to distinguish the different trajectories and their initial positions are marked by a gray square. A 3D plot may be helpful in viewing particles at varying depths.

## Notebooks¶

If you would like to see more examples of particle tracking, feel free to look at the following notebook:

## References¶

• Manual: Compilation and Installation
• Manual: Ariane Namelist
• Manual: Ariane Tutorial
• Blanke, B., and S. Raynaud, 1997: Kinematics of the Pacific Equatorial Undercurrent: a Eulerian and Lagrangian approach from GCM results. J. Phys. Oceanogr., 27, 1038-1053.
• Blanke, B., M. Arhan, G. Madec, and S. Roche, 1999: Warm water paths in the equatorial Atlantic as diagnosed with a general circulation model. J. Phys. Oceanogr., 29, 2753-2768.
• Blanke, B., S. Speich, G. Madec, and K. Döös, 2001: A global diagnostic of interocean mass transfers. J. Phys. Oceanogr., 31, 1623-1632.