.. DO NOT EDIT. .. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY. .. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE: .. "gallery/Contours/NCL_conOncon_2.py" .. LINE NUMBERS ARE GIVEN BELOW. .. only:: html .. note:: :class: sphx-glr-download-link-note :ref:`Go to the end ` to download the full example code. .. rst-class:: sphx-glr-example-title .. _sphx_glr_gallery_Contours_NCL_conOncon_2.py: NCL_conOncon_2.py ================= This script illustrates the following concepts: - Overlaying two sets of contours on a map - Drawing the zero contour line thicker - Changing the center longitude for a cylindrical equidistant projection - Using a blue-white-red color map See following URLs to see the reproduced NCL plot & script: - Original NCL script: https://www.ncl.ucar.edu/Applications/Scripts/conOncon_2.ncl - Original NCL plot: https://www.ncl.ucar.edu/Applications/Images/conOncon_2_lg.png .. GENERATED FROM PYTHON SOURCE LINES 16-17 Import packages: .. GENERATED FROM PYTHON SOURCE LINES 17-28 .. code-block:: Python import numpy as np import xarray as xr import matplotlib.pyplot as plt import cartopy.crs as ccrs import cartopy.feature as cfeature from cartopy.mpl.gridliner import LongitudeFormatter, LatitudeFormatter import cmaps import geocat.datafiles as gdf import geocat.viz as gv .. GENERATED FROM PYTHON SOURCE LINES 29-30 Read in data: .. GENERATED FROM PYTHON SOURCE LINES 30-43 .. code-block:: Python # Open a netCDF data file using xarray default engine and load the data into xarrays sst = xr.open_dataset(gdf.get("netcdf_files/sst8292a.nc")) olr = xr.open_dataset(gdf.get("netcdf_files/olr7991a.nc")) # Extract data for December 1982 sst = sst.isel(time=11, drop=True).SSTA olr = olr.isel(time=47, drop=True).OLRA # Fix the artifact of not-shown-data around 0 and 360-degree longitudes sst = gv.xr_add_cyclic_longitudes(sst, 'lon') olr = gv.xr_add_cyclic_longitudes(olr, 'lon') .. GENERATED FROM PYTHON SOURCE LINES 44-45 Plot: .. GENERATED FROM PYTHON SOURCE LINES 45-146 .. code-block:: Python # Generate figure and axes plt.figure(figsize=(8, 8)) # Set axes projection ax = plt.axes(projection=ccrs.PlateCarree(central_longitude=-160)) ax.set_extent([100, 300, -60, 60], crs=ccrs.PlateCarree()) # Load in color map and specify contour levels cmap = cmaps.BlWhRe sst_levels = np.arange(-5.5, 6, 0.5) # Draw SST contour temp = sst.plot.contourf( ax=ax, transform=ccrs.PlateCarree(), cmap=cmap, levels=sst_levels, extend='neither', add_colorbar=False, add_labels=False, zorder=0, ) plt.colorbar( temp, ax=ax, orientation='vertical', ticks=np.arange(-5, 6, 1), drawedges=True, shrink=0.5, aspect=10, ) # Draw map features on top of filled contour ax.add_feature(cfeature.LAND, facecolor='lightgray', zorder=1) ax.add_feature(cfeature.COASTLINE, edgecolor='gray', linewidth=0.5, zorder=1) # Draw OLR contour # Specify contour levels excluding 0 olr_levels = np.arange(-80, 0, 10) olr_levels = np.append(olr_levels, np.arange(10, 50, 10)) rad = olr.plot.contour( ax=ax, transform=ccrs.PlateCarree(), levels=olr_levels, colors='gray', linewidths=0.5, add_labels=False, ) ax.clabel(rad, [-40, -20, 20], fmt='%d', inline=True, colors='black') # Plot the zero contour with a black color rad = olr.plot.contour( ax=ax, transform=ccrs.PlateCarree(), levels=[0], colors='black', linewidths=0.5, add_labels=False, ) ax.clabel(rad, [0], fmt='%d', inline=True, colors='black') # Use geocat.viz.util convenience function to set axes tick values gv.set_axes_limits_and_ticks( ax, ylim=(-60, 60), yticks=np.arange(-60, 90, 30), xticks=np.arange(-80, 120, 30) ) # 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) # Remove the degree symbol from tick labels ax.yaxis.set_major_formatter(LatitudeFormatter(degree_symbol='')) ax.xaxis.set_major_formatter(LongitudeFormatter(degree_symbol='')) # Use geocat.viz.util convenience function to add minor and major tick lines gv.add_major_minor_ticks(ax, x_minor_per_major=3, y_minor_per_major=3, labelsize=10) gv.set_titles_and_labels( ax, maintitle=olr.long_name, maintitlefontsize=14, lefttitle='degC', lefttitlefontsize=12, righttitle='(W m s$^{-2}$)', righttitlefontsize=12, ) # Add center title ax.text(0.35, 1.06, 'December 1982', fontsize=12, transform=ax.transAxes) # Add lower text box ax.text( 1, -0.2, "CONTOUR FROM -80 TO 40 BY 10", horizontalalignment='right', transform=ax.transAxes, bbox=dict(boxstyle='square, pad=0.25', facecolor='white', edgecolor='black'), ) plt.show() .. image-sg:: /gallery/Contours/images/sphx_glr_NCL_conOncon_2_001.png :alt: degC, Outgoing Longwave Radiation Anomalies, (W m s$^{-2}$) :srcset: /gallery/Contours/images/sphx_glr_NCL_conOncon_2_001.png :class: sphx-glr-single-img .. rst-class:: sphx-glr-timing **Total running time of the script:** (0 minutes 3.657 seconds) .. _sphx_glr_download_gallery_Contours_NCL_conOncon_2.py: .. only:: html .. container:: sphx-glr-footer sphx-glr-footer-example .. container:: sphx-glr-download sphx-glr-download-jupyter :download:`Download Jupyter notebook: NCL_conOncon_2.ipynb ` .. container:: sphx-glr-download sphx-glr-download-python :download:`Download Python source code: NCL_conOncon_2.py ` .. container:: sphx-glr-download sphx-glr-download-zip :download:`Download zipped: NCL_conOncon_2.zip ` .. only:: html .. rst-class:: sphx-glr-signature `Gallery generated by Sphinx-Gallery `_