# 2.1. Parameter file¶

The working of PyPAGO is based on a Python parameter file, which contains the variables needed by the program. The default parameter file (dedicated to the analysis of the NEMO model) is shown below.

Prior to run PyPAGO analysis, the user is requiered to create, in the working directory, a param.py file, which will overwrite these default parameters.

The most critical variable is the dictvname directory, which contains the names of the coordinate and scale factor variables and which will dictate the behaviour of PyPAGO, as detailed below.

Warning

The variables defined in the dictvname dictionnary are required and must all be included in a unique file (mesh_mask.nc for instance).


"""
This program contains the main settings of |pypago|
associated with the NEMO model.
"""

import sys
import numpy as np
import pylab as plt
import matplotlib as mp
from mpl_toolkits.basemap import pyproj

######################################################## Output redirection

# Uncomment below to change the outputs
# and erros locations.
sys.stdout = sys.stdout
sys.stderr = sys.stdout

######################################################## Scale variables

# List of model variable names stored
# as a dictionary
dictvname = {}
dictvname["lon_varname"] = "glamt"  # longitude
dictvname["lat_varname"] = "gphit"  # latitude
dictvname["depth_varname"] = "gdept_0"  # 1D depth array
dictvname["mbathy_varname"] = "mbathy"   # last layer index

dictvname["dxt_varname"] = "e1t"  # zonal width of t-cells
dictvname["dyt_varname"] = "e2t"  # meridional width of t-cells
dictvname["dye_varname"] = "e2u"  # meridional width of u-cells
dictvname["dxn_varname"] = "e1v"  # zonal width of v-cells
dictvname["dzt_varname"] = "e3t"   # height of t-cells
dictvname["dze_varname"] = "e3u"    # height of u-cells
dictvname["dzn_varname"] = "e3v"  # height of v-cells
dictvname["time_varname"] = "time_counter"  # height of v-cells

# used only if the e3t variable is 2D
# (height of the last ocean layer)
# dictvname["bathy_varname"] = "ht"   # bathymetry
# dictvname["dzt1d_varname"] = "e3t_0"

######################################################## Settings for diagnostics

rho0_c = 4.186e6  # for heat transport calculations
S0 = 34.8  # reference salinity for freshwater calculations

lev1 = 500  # first depth interval from surface down to lev1
lev2 = 1000  # second depth interval from lev1 down to lev2
lev3 = 2000  # third depth interval from lev2 m down to lev3 m

# Sigma vectors (used in density related transport indices, not implemented yet)
sigma0_vec_lr = np.array([24, 24.4, 24.9, 25.4, 25.9, 26.4,
26.75, 27.05, 27.30, 27.45, 27.58, 27.68, 27.75,
27.80, 27.83, 27.86, 27.89, 27.92, 27.95, 27.98,
28.01, 28.04, 28.07, 28.1, 28.6, 29.1])

sigma0_vec_hr = np.array([24, 24.2, 24.4, 24.65, 24.9, 25.15, 25.4, 25.65,
25.9, 16.15, 26.4, 16.57, 26.75, 26.90, 27.05, 27.17,
27.30, 27.37, 27.45, 27.52, 27.58,
27.63, 27.68, 27.72, 27.75, 27.78, 27.80, 27.815,
27.83, 27.845, 27.86, 27.875, 27.89,
27.905, 27.92, 27.935, 27.95, 27.965,
27.98, 27.99, 28.01, 28.025,
28.04, 28.055, 28.07, 28.085, 28.1, 28.35,
28.6, 28.8, 29.1])

sigma2_vec = np.array([34.4, 34.6, 34.8, 35, 35.2, 35.4, 36, 36.4,
36.6, 36.7, 36.8, 36.9, 36.95, 37, 37.05,
37.1, 37.15, 37.2, 37.4, 37.6, 38])

sigma1_vec = np.arange(29.68, 34.6800+1, 1)

######################################################## Settings for figures

mp.rcParams['lines.linewidth'] = 1.  # line width
mp.rcParams['text.usetex'] = False  # no latex in matplotlib

left = 0.07
right = 0.99
wspace = 0.07
top = 0.93
bottom = 0.03
figsize = (11, 4)
bgcolor = 'black'
cmapt = plt.cm.get_cmap('jet')
cmaps = plt.cm.get_cmap('jet')
cmapv = plt.cm.get_cmap('RdBu_r')

######################################################## Settings for projection (change carefully)

ee = pyproj.Geod(ellps='GRS80')  # ellipsoid used for distance calculation


## 2.1.1. NEMO model¶

Table 2.1 Grid variables for the NEMO model
Variable Name Description
time_varname time_counter Time variable
lon_varname glamt Longitude
lat_varname gphit Latitude
dxt_varname e1t Zonal width of T points
dyt_varname e2t Meridional width of T points
dye_varname e2u Meridional width of V points
dxn_varname e1v Zonal width of U points
dzt_varname e3t Height of T points

bathy_varname ht Bathymetry (None if not defined in the file)
depth_varname gdept_1d 1D depth array
mbathy_varname mbathy 2D array of k-indexes of the last ocean points

dzt1d_varname e3t_0 1-D scale factor
dze_varname e3u Height of U points (None if not defined in the file)
dzn_varname e3v Height of V points (None if not defined in the file)

### 2.1.1.1. Recontruction of the bathymetry¶

If the bathy_varname is None, bathymetry is reconstructed from the depth_varname and the mbathy_varname variables

### 2.1.1.2. Recontruction of the vertical scale factors¶

The reconstruction of the vertical scale factors depend on the shape of the dzt variable.

• If it is 1D, it is assumed that there are no partial steps, and dzt is tiled along the longitude and latitude dimensions. And the dzw and dzn variables are set equal to dzt.
• If it is 2D, then a 3D dzt variable is reconstructed by using the pypago.coords.NemoCoords.create_3d_e3t() function. This function needs the 1D scale factor variable, whose name is defined by the dzt1d_varname variable. Then, if the dze_varname and dzn_varname variables are not None, these variables are read. Else, they are reconstructed from the 3D dzt variable by using the pypago.coords.NemoCoords.reconstruct_3d_e3uv() function. Finally, the dzw variable is reconstructed from the dze variable.

## 2.1.2. ROMS model¶

Table 2.2 Grid variables for the ROMS model
Variable Name Description
time_varname time Time variable
bathy_varname h Bathymetry
lon_varname lon_rho Longitude of T points
lat_varname lat_rho Latitude of T points
dxt_varname pm Zonal width of T points
dyt_varname pn Merdional width of T points

dxs_varname pm Zonal width of U points (southern face)
dyw_varname pn Meridional width of V points (western face)

roms_nsigma   Number of sigma levels

### 2.1.2.1. Reconstruction of horizontal scale factors¶

In ROMS model, U points are located on the western faces, while V points are located on the southern faces. Therefore, the dzn variable is reconstructed by shifting the dzs variable.

### 2.1.2.2. Recontruction of the vertical scale factors¶

Since ROMS is a $$\sigma$$ model, vertical scale factors is set equal to 1. Since the number of $$\sigma$$ levels is stored in the data file, the user has to define it in the param.py file so that the dzt, dzn and dzw variables are defined with the right dimensions.

Todo

Complete for all the other models