NCL_animate_1.py

This script illustrates the following concepts:

• Creating animations using matplotlib.FuncAnimation

See following URLs to see the reproduced NCL plot & script:

• Original NCL script: https://www.ncl.ucar.edu/Applications/Scripts/animate_1.ncl

• Original NCL plot: https://www.ncl.ucar.edu/Applications/Images/animate_1_1_lg.png

Please note:

Executing this script will not display a gif, but you have the option to uncomment a line at the bottom that will save a gif in the same directory as this script.

Import packages:

import cartopy.crs as ccrs
import matplotlib.animation as animation
import numpy as np
import xarray as xr
from matplotlib import pyplot as plt

import geocat.datafiles as gdf
import geocat.viz.util as gvutil

Read in data:

# Open a netCDF data file using xarray default engine and load the data into xarrays
# Disable time decoding due to missing necessary metadata
ds = xr.open_dataset(gdf.get("netcdf_files/meccatemp.cdf"), decode_times=False)

tas = ds.t

Create animation:

fig = plt.figure(figsize=(10, 8))
# Generate axes using Cartopy and draw coastlines
ax = plt.axes(projection=ccrs.PlateCarree(central_longitude=150))
ax.coastlines(linewidths=0.5)
ax.set_extent([-180, 180, -90, 90], ccrs.PlateCarree())

# Use geocat.viz.util convenience function to set axes limits & tick values
gvutil.set_axes_limits_and_ticks(ax,
                                 xlim=(-180, 180),
                                 ylim=(-90, 90),
                                 xticks=np.linspace(-180, 180, 13),
                                 yticks=np.linspace(-90, 90, 7))

# Use geocat.viz.util convenience function to add minor and major tick lines
gvutil.add_major_minor_ticks(ax, labelsize=10)

# Use geocat.viz.util convenience function to make latitude, longitude tick labels
gvutil.add_lat_lon_ticklabels(ax)

# create initial plot that establishes a colorbar
tas[0, :, :].plot.contourf(ax=ax,
                           transform=ccrs.PlateCarree(),
                           vmin=195,
                           vmax=328,
                           levels=53,
                           cmap="inferno",
                           cbar_kwargs={
                               "extendrect": True,
                               "orientation": "horizontal",
                               "ticks": np.arange(195, 332, 9),
                               "label": "",
                               "shrink": 0.90
                           })


# animate function for matplotlib FuncAnimation
def animate(i):
    tas[i, :, :].plot.contourf(
        ax=ax,
        transform=ccrs.PlateCarree(),
        vmin=195,
        vmax=328,
        levels=53,
        cmap="inferno",
        add_colorbar=False,
    )

    gvutil.set_titles_and_labels(
        ax,
        maintitle="January Global Surface Temperature (K) - Day  " +
        str(tas.coords['time'].values[i])[:13],
        xlabel="",
        ylabel="")


# runs the animation initiated with the frame from init and progressed with the animate function
anim = animation.FuncAnimation(fig, animate, frames=30, interval=200)

# Uncomment this line to save the created animation
anim.save('animate_1.gif', writer='pillow', fps=5)

Once Loop Reflect

Out:

/home/docs/checkouts/readthedocs.org/user_builds/geocat-examples/conda/v2022.5.0/lib/python3.8/site-packages/cartopy/io/__init__.py:241: DownloadWarning: Downloading: https://naturalearth.s3.amazonaws.com/110m_physical/ne_110m_coastline.zip
  warnings.warn(f'Downloading: {url}', DownloadWarning)