Analysis task for line plot of zonal means

[kevinrosa]

This is a reminder about adding the ability to plot zonal means of fields such as SST, EKE, etc.

If the field has already been remapped by MPAS-Analysis, this task is trivial:

# open remapped MPAS:
fname = 'clim/mpas/remapped/eke_oQU15_to_0.5x0.5degree/mpaso_ANN_000101_000112_climo.nc'
qu15 = xr.open_dataset(fname)

# open remapped observations:
fname = 'clim/obs/remapped/eke_0.25x0.25degree_to_0.5x0.5degree_ANN.nc'
obs = xr.open_dataset(fname)

plt.plot(obs.latitude, obs.eke.mean(dim='longitude').squeeze(),'k')
plt.plot(qu15.lat, qu15.eke.mean(dim='lon').squeeze(), 'r')

plt.gca().legend(('Observations','QU15'))
plt.xlabel('Latitude ($^o$ N)')
plt.ylabel('EKE (cm$^2$/s$^2$)')