Python contour filled plot

Software requirements:

• Python 3

• numpy

• xarray

• matplotlib

• cartopy

Example script

matplotlib_contour_filled.py

#!/usr/bin/env python
# coding: utf-8
'''
DKRZ example

This example demonstrates how to plot filled contours on a map, and add a colorbar.

Content

- draw map
- draw coastlines, state borders and provinces
- draw filled contours
- add colorbar
- save to PNG

-------------------------------------------------------------------------------
2021 copyright DKRZ licensed under CC BY-NC-SA 4.0 <br>
               (https://creativecommons.org/licenses/by-nc-sa/4.0/deed.en)
-------------------------------------------------------------------------------
'''
import numpy as np
import xarray as xr
import matplotlib.pyplot as plt
import cartopy.crs as ccrs
import cartopy.feature as cfeature

def main():
    #-- open data set
    ds = xr.open_dataset('../../data/rectilinear_grid_2D.nc')

    #-- create states outlines
    provinces = cfeature.NaturalEarthFeature(category='cultural',
                                             name='admin_1_states_provinces_lines',
                                             scale='50m',
                                             facecolor='none')
    plt.switch_backend('agg')

    #-- create figure and axes object
    fig, ax = plt.subplots(figsize=(12,12), subplot_kw=dict(projection=ccrs.PlateCarree()))

    #-- add coastlines, country border lines, and grid lines
    ax.coastlines(zorder=1)
    ax.add_feature(cfeature.BORDERS, linewidth=0.6, edgecolor='gray', zorder=2)
    ax.add_feature(provinces, edgecolor='gray', zorder=3)
    ax.gridlines(draw_labels=True,
                 linewidth=0.5,
                 color='gray',
                 xlocs=range(-180,180,30),
                 ylocs=range(-90,90,30),
                 zorder=4)

    #-- add title
    ax.set_title('Temperature', fontsize=12, fontweight='bold')

    #-- create contour line plot
    cnplot = ax.contourf(ds.lon, ds.lat, ds.tsurf.isel(time=0),
                         cmap='jet',
                         levels=15,
                         zorder=0,
                         transform=ccrs.PlateCarree())

    #-- add colorbar
    cbar = plt.colorbar(cnplot, orientation='horizontal', pad=0.05, shrink=0.7)
    cbar.set_label('K')

    #-- save graphic output to PNG file
    plt.savefig('plot_matplotlib_contour_filled_rect.png',
                 bbox_inches='tight',
                 dpi=100)

if __name__ == '__main__':
    main()

Plot result