Plot MPIOM GR15 with Python

#!/usr/env/python

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

file='/pool/data/MPIOM/GR15/GR15L40_fx.nc'
ds=xr.open_dataset(file,decode_times=False)
area=ds['area'].values
area=np.squeeze(area)
lat=ds['lat'].values
lon=ds['lon'].values
factor=1/1000000

def circlemap(ax):
    '''
    This makes the cicular frame for Arctic maps.
    '''
    import numpy as np
    import matplotlib.path as mpath
    theta = np.linspace(0, 2*np.pi, 100)
    center, radius = [0.5, 0.5], 0.5
    verts = np.vstack([np.sin(theta), np.cos(theta)]).T
    circle = mpath.Path(verts * radius + center)
    ax.set_boundary(circle, transform=ax.transAxes)


fig = plt.figure(figsize=(14, 10))
ax = fig.add_subplot(111,projection=ccrs.NorthPolarStereo())
ax.set_extent([-180, 180, 63, 90], crs=ccrs.PlateCarree())
ax.coastlines() 
ps.circlemap(ax) # comment to remove the circular frame

mesh = ax.pcolormesh(lon, lat, area*factor, cmap='Blues', transform=ccrs.PlateCarree(),
#                      antialiased=True, edgecolor='k', linewidth=0.3, # Uncomment to show lines for grid-cell boundarie
                     vmin=0, vmax=10000,)
cbar=plt.colorbar(mesh, orientation='vertical', shrink=0.75)
cbar.set_label('grid-cell area [km$^2$]',fontsize=16)
cbar.ax.tick_params(labelsize=14)
plt.show()