NCL_proj_3.pyΒΆ

This script illustrates the following concepts:
  • Drawing filled contours over an orthographic map

  • Changing the center latitude and longitude for an orthographic projection

  • Turning off map fill

See following URLs to see the reproduced NCL plot & script:
import cartopy.crs as ccrs
import geocat.datafiles as gdf
import matplotlib.pyplot as plt

Import packages:

import numpy as np
import xarray as xr
from geocat.viz import util as gvutil

Read in data:

# Open a netCDF data file using xarray default engine and load the data into xarrays
ds = xr.open_dataset(gdf.get("netcdf_files/atmos.nc"), decode_times=False)
t = ds.TS.isel(time=0)

Fix the artifact of not-shown-data around 0 and 360-degree longitudes

wrap_t = gvutil.xr_add_cyclic_longitudes(t, "lon")

Plot:

# Generate figure (set its size (width, height) in inches)
fig = plt.figure(figsize=(10, 10))

# Generate axes using Cartopy and draw coastlines with
ax = plt.axes(
    projection=ccrs.Orthographic(central_longitude=-120, central_latitude=50))

# Set extent to include latitudes between 0 and 90, and longitude between
# 0 and -180 only
ax.set_extent([0, -180, 0, 90], ccrs.PlateCarree())
ax.set_global()
ax.coastlines(linewidths=0.5)

# Plot data and add a colorbar
temp = wrap_t.plot.contourf(ax=ax,
                            transform=ccrs.PlateCarree(),
                            levels=11,
                            cmap='coolwarm',
                            add_colorbar=False)

cbar_ticks = np.arange(210, 311, 10)
cbar = plt.colorbar(temp,
                    orientation='horizontal',
                    shrink=0.75,
                    pad=0.05,
                    extendrect=True,
                    ticks=cbar_ticks)

cbar.ax.tick_params(labelsize=10)

# Use geocat.viz.util convenience function to add titles to left and right
# of the plot axis.
gvutil.set_titles_and_labels(ax,
                             maintitle="Example of Orthogonal Projection",
                             lefttitle="Surface Temperature",
                             righttitle="K")

# Show the plot
plt.show()
Surface Temperature, Example of Orthogonal Projection, K

Total running time of the script: ( 0 minutes 0.560 seconds)

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