Potential energy tutorial

Potential energy tutorial example.

  6 minute read  

A demonstration to calculate the Potential Energy Anomaly and demonstrate regional masking with MaskMaker

Relevant imports and filepath configuration

import coast
import numpy as np
import os
import matplotlib.pyplot as plt
import matplotlib.colors as colors  # colormap fiddling
import xarray as xr

/usr/share/miniconda/envs/coast/lib/python3.10/site-packages/pydap/lib.py:5: DeprecationWarning: pkg_resources is deprecated as an API. See https://setuptools.pypa.io/en/latest/pkg_resources.html
/usr/share/miniconda/envs/coast/lib/python3.10/site-packages/pkg_resources/__init__.py:2871: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('pydap')`.
Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
/usr/share/miniconda/envs/coast/lib/python3.10/site-packages/pkg_resources/__init__.py:2871: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('pydap.responses')`.
Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
/usr/share/miniconda/envs/coast/lib/python3.10/site-packages/pkg_resources/__init__.py:2350: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('pydap')`.
Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
/usr/share/miniconda/envs/coast/lib/python3.10/site-packages/pkg_resources/__init__.py:2871: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('pydap.handlers')`.
Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
/usr/share/miniconda/envs/coast/lib/python3.10/site-packages/pkg_resources/__init__.py:2350: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('pydap')`.
Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
/usr/share/miniconda/envs/coast/lib/python3.10/site-packages/pkg_resources/__init__.py:2871: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('pydap.tests')`.
Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
/usr/share/miniconda/envs/coast/lib/python3.10/site-packages/pkg_resources/__init__.py:2350: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('pydap')`.
Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages
/usr/share/miniconda/envs/coast/lib/python3.10/site-packages/pkg_resources/__init__.py:2871: DeprecationWarning: Deprecated call to `pkg_resources.declare_namespace('sphinxcontrib')`.
Implementing implicit namespace packages (as specified in PEP 420) is preferred to `pkg_resources.declare_namespace`. See https://setuptools.pypa.io/en/latest/references/keywords.html#keyword-namespace-packages

# set some paths
root = "./"
dn_files = root + "./example_files/"
fn_nemo_grid_t_dat = dn_files + "nemo_data_T_grid_Aug2015.nc"
fn_nemo_dom = dn_files + "coast_example_nemo_domain.nc"
config_t = root + "./config/example_nemo_grid_t.json"

Loading data

# Create a Gridded object and load in the data:
nemo = coast.Gridded(fn_nemo_grid_t_dat, fn_nemo_dom, config=config_t)

Calculates Potential Energy Anomaly

The density and depth averaged density can be supplied within gridded_t as density and density_bar DataArrays, respectively. If they are not supplied they will be calculated. density_bar is calcuated using depth averages of temperature and salinity.

# Compute a vertical max to exclude depths below 200m
Zd_mask, kmax, Ikmax = nemo.calculate_vertical_mask(200.)

# Initiate a stratification diagnostics object
strat = coast.GriddedStratification(nemo)

/usr/share/miniconda/envs/coast/lib/python3.10/site-packages/xarray/core/utils.py:494: FutureWarning: The return type of `Dataset.dims` will be changed to return a set of dimension names in future, in order to be more consistent with `DataArray.dims`. To access a mapping from dimension names to lengths, please use `Dataset.sizes`.

# calculate PEA for unmasked depths
strat.calc_pea(nemo, Zd_mask)

make a plot

strat.quick_plot('PEA')

(<Figure size 1000x1000 with 2 Axes>,
 <Axes: title={'center': '01 Aug 2015: Potential Energy Anomaly (J / m^3)'}, xlabel='longitude', ylabel='latitude'>)

png

strat.dataset

<xarray.Dataset>
Dimensions:    (t_dim: 7, y_dim: 375, x_dim: 297)
Coordinates:
time       (t_dim) datetime64[ns] 2015-08-01T12:00:00 … 2015-08-07T12:0…
latitude   (y_dim, x_dim) float32 40.07 40.07 40.07 40.07 … 65.0 65.0 65.0
longitude  (y_dim, x_dim) float32 -19.89 -19.78 -19.67 … 12.78 12.89 13.0
Dimensions without coordinates: t_dim, y_dim, x_dim
Data variables:
PEA        (t_dim, y_dim, x_dim) float64 nan nan nan nan … nan nan nan nan