Map Projection (using Cartopy)

This page introduces a program that plots monthly temperature at each station on a map.

Monthly dataset

If data has a higher time resolution than the monthly average, you need to calculate the monthly average.

    # Monthly average
    m1 = df1.resample('1M').mean()

Monthly temperature plots on a map

Cartopy install

The map projection uses cartopy package.

The information on cartopy installation is available here.

You can simply command $ conda install -n env_weclim -c conda-forge cartopy.

Map plots

The background map can be drawn using the following commends:

import cartopy.crs as crs

    plt.rcParams.update({'font.size': 15})

    # map projections and state boundary lines
    ax = fig.add_subplot(1,1,1, projection=crs.PlateCarree())
    ax.stock_img()
    ax.add_feature(cfeature.STATES)

    # map area setting
    ax.set_extent([-115, -108, 36, 43],

The monthly temperature can be plots at each location using pandas.DataFrame.plot command (command information).

    # Define dictionary for kwargs
    kwargs = dict(
      vmin = -20.0,
      vmax = 40.0,
      transform=crs.PlateCarree(),  # ds projection
    )

    # add grid
    ax.gridlines(draw_labels=True, crs=crs.PlateCarree())
 
    dfig.plot(x="Lon", y="Lat", kind="scatter", c="TAIR",
      title = "Air Temperature ("+titleX+")", s=200, 
      colormap="jet",  ax=ax, **kwargs)

    plt.draw()

Sample program for maps

Source file: maps.temp.py

Create animation

PNG files can be converted to animated images (gif file).

convert -delay 50 -loop 3 ${figdir}/*.png TAIR.gif

Here, -delay N is the frame rate of N/100 (seconds) and -loop M is the number of loop of the animation image.

You can check the animation image as $ animate XX.gif.

Gallery

Monthly temperature at each weather station (oC).