* cartopy (http://scitools.org.uk/cartopy/)
"""
import cartopy.crs as ccrs
from netCDF4 import Dataset
import matplotlib.pyplot as plt
import numpy as np
from eofs.standard import Eof
from eofs.examples import example_data_path
# Read geopotential height data using the netCDF4 module. The file contains
# December-February averages of geopotential height at 500 hPa for the
# European/Atlantic domain (80W-40E, 20-90N).
filename = example_data_path('hgt_djf.nc')
ncin = Dataset(filename, 'r')
z_djf = ncin.variables['z'][:]
lons = ncin.variables['longitude'][:]
lats = ncin.variables['latitude'][:]
ncin.close()
# Compute anomalies by removing the time-mean.
z_djf_mean = z_djf.mean(axis=0)
z_djf = z_djf - z_djf_mean
# Create an EOF solver to do the EOF analysis. Square-root of cosine of
# latitude weights are applied before the computation of EOFs.
coslat = np.cos(np.deg2rad(lats)).clip(0., 1.)
wgts = np.sqrt(coslat)[..., np.newaxis]
solver = Eof(z_djf, weights=wgts)
* cartopy (http://scitools.org.uk/cartopy/)
"""
import cartopy.crs as ccrs
import cartopy.feature as cfeature
import matplotlib.pyplot as plt
import numpy as np
import xarray as xr
from eofs.xarray import Eof
from eofs.examples import example_data_path
# Read SST anomalies using the xarray module. The file contains November-March
# averages of SST anomaly in the central and northern Pacific.
filename = example_data_path('sst_ndjfm_anom.nc')
sst = xr.open_dataset(filename)['sst']
# Create an EOF solver to do the EOF analysis. Square-root of cosine of
# latitude weights are applied before the computation of EOFs.
coslat = np.cos(np.deg2rad(sst.coords['latitude'].values))
wgts = np.sqrt(coslat)[..., np.newaxis]
solver = Eof(sst, weights=wgts)
# Retrieve the leading EOF, expressed as the correlation between the leading
# PC time series and the input SST anomalies at each grid point, and the
# leading PC time series itself.
eof1 = solver.eofsAsCorrelation(neofs=1)
pc1 = solver.pcs(npcs=1, pcscaling=1)
# Plot the leading EOF expressed as correlation in the Pacific domain.
