.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "gallery/Contours/NCL_ce_1.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_gallery_Contours_NCL_ce_1.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_gallery_Contours_NCL_ce_1.py:


NCL_ce_1.py
===========
This script illustrates the following concepts:
   - Drawing black-and-white contours over a cylindrical equi-distant map
   - Specifying contour labels

See following URLs to see the reproduced NCL plot & script:
    - Original NCL script: https://www.ncl.ucar.edu/Applications/Scripts/ce_1.ncl
    - Original NCL plot: https://www.ncl.ucar.edu/Applications/Images/ce_1_lg.png

.. GENERATED FROM PYTHON SOURCE LINES 14-15

Import packages:

.. GENERATED FROM PYTHON SOURCE LINES 15-25

.. code-block:: Python

    import numpy as np
    import xarray as xr
    import cartopy.crs as ccrs
    import matplotlib.pyplot as plt
    import cartopy.feature as cfeature
    from cartopy.mpl.gridliner import LongitudeFormatter, LatitudeFormatter

    import geocat.datafiles as gdf
    import geocat.viz as gv








.. GENERATED FROM PYTHON SOURCE LINES 26-27

Read in data:

.. GENERATED FROM PYTHON SOURCE LINES 27-31

.. code-block:: Python


    # Open a netCDF data file using xarray default engine and load the data into xarrays, choosing the 2nd timestamp
    ds = xr.open_dataset(gdf.get("netcdf_files/uv300.nc")).isel(time=1)








.. GENERATED FROM PYTHON SOURCE LINES 32-33

Plot:

.. GENERATED FROM PYTHON SOURCE LINES 33-100

.. code-block:: Python


    # Generate figure (set its size (width, height) in inches)
    fig = plt.figure(figsize=(12, 6))

    # Generate axes using Cartopy projection
    projection = ccrs.PlateCarree()
    ax = plt.axes(projection=projection)

    # Draw land
    ax.add_feature(cfeature.LAND, color='silver')

    # Define the contour levels
    levels = np.arange(-12, 41, 4)

    # Draw contour lines
    contour = ds.U.plot.contour(
        ax=ax,
        levels=levels,
        xticks=np.arange(-180, 181, 30),  # nice x ticks
        yticks=np.arange(-90, 91, 30),  # nice y ticks
        transform=projection,  # ds projection
        add_labels=False,  # turn off xarray's automatic Lat, lon labels
        colors="black",  # note plurals in this and following kwargs
        linestyles="-",
        linewidths=0.5,
    )

    # Label the contours and set axes title
    ax.clabel(contour, [-8, 0, 8, 16, 24, 32], fontsize=12, fmt="%.0f")

    # Add lower text box
    ax.text(
        0.995,
        -0.13,
        "CONTOUR FROM -12 TO 40 BY 4",
        horizontalalignment='right',
        transform=ax.transAxes,
        fontsize=14,
        bbox=dict(boxstyle='square, pad=0.25', facecolor='white', edgecolor='black'),
    )

    # Use geocat.viz.util convenience function to add minor and major tick lines
    gv.add_major_minor_ticks(ax)

    # Use geocat.viz.util convenience function to make plots look like NCL plots by using latitude, longitude tick labels
    gv.add_lat_lon_ticklabels(ax)

    # Removing degree symbol from tick labels to resemble NCL example
    ax.yaxis.set_major_formatter(LatitudeFormatter(degree_symbol=''))
    ax.xaxis.set_major_formatter(LongitudeFormatter(degree_symbol=''))

    # Use geocat.viz.util convenience function to add left and right title to the plot axes.
    gv.set_titles_and_labels(
        ax,
        lefttitle="Zonal Wind",
        lefttitlefontsize=16,
        righttitle=ds.U.units,
        righttitlefontsize=16,
    )

    # Set ticklabel fontsize
    plt.xticks(fontsize=14)
    plt.yticks(fontsize=14)

    # Show plot
    plt.tight_layout()
    plt.show()



.. image-sg:: /gallery/Contours/images/sphx_glr_NCL_ce_1_001.png
   :alt: Zonal Wind, m/s
   :srcset: /gallery/Contours/images/sphx_glr_NCL_ce_1_001.png
   :class: sphx-glr-single-img






.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 0.650 seconds)


.. _sphx_glr_download_gallery_Contours_NCL_ce_1.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: NCL_ce_1.ipynb <NCL_ce_1.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: NCL_ce_1.py <NCL_ce_1.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: NCL_ce_1.zip <NCL_ce_1.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_