Python/PlotMetData

Plotting Meteorological Data with Python

This is a very brief introduction to using pygrib and NetCDFFile in order to plot met data in Python. Note that you should read the PythonPaths section in order to be sure that you'll be able to import the appropriate modules.

Let's get started with some test data::

   mkdir test
   cd test
   cp ~sec/kleinproject/FUKU/geop_april* .
   

Now, start ipython in your shell, or create a python file in the test directory::

   ipython
   

Next, let's take care of some basic imports::

import matplotlib.pyplot as plt
import pygrib
from netCDF4 import Dataset as NetCDFFile

Now, we'll write some python code to plot the netcdf variables::

nci = NetCDFFile('geopot_april_01.nc')
nci.variables #will print a listing of the variables (note: nci.variables is a dictionary)
z = nci.variables['z']
z.shape  #what shape is the 'z' array?

for i in range(3):
    plt.figure()
    plt.imshow(z[0,i,:,:]) #we take the i'th slab
    plt.title('netcdf geopot {0}'.format(i))
    plt.colorbar()
    plt.savefig('nc_geopot_{}'.format(i))

Now, let's take a look at the grib data::

grbs = pygrib.open('geop_april_01_2011.grib')
for grb in grbs:
    grb

This will print a listing of all the gribs in the grib file. Make sure we reset the grbs back to the beginning::

grbs.seek(0)
ghs = grbs.select(name='Geopotential')

for i,grb in enumerate(ghs):
    plt.figure()
    g = grb
    plt.imshow(g.values)
    title = g.name + ' at level ' + str(g.level) + ' [' + g.units + ']'
    plt.title(title)
    plt.colorbar()
    plt.savefig(g.name + str(i) +  '.png')

That's it! In your folder you should have some test plots.