Add examples for working with Lambert Azimuthal projection (UKV, MOGREPS-UK)

[AlexHilson]

Code along the lines of the following can be used to turn the lambert azimuthal x / y co-ordinates into lat/lon. It'd be good to get a full example up to show one way of working with regional UK model data.

import pyproj
p = pyproj.Proj("+proj=laea +lon_0=-2.5 +lat_0=54.9 +x_0=0.0 +y_0=0.0 +ellps=GRS80")
# lon, lat = p(x, y, inverse=True)
lon, lat = p(-36000, -158000, inverse=True)
print (lat, lon)

53.47926025120268 -3.0422171310489534

Originally posted by @boristyukin in #19 (comment)

[AlexHilson]

Iris regridding docs are at https://scitools.org.uk/iris/docs/latest/userguide/interpolation_and_regridding.html. If the Global data works for you but the UKV data doesn't, this would be one easy method of translating the UKV grid into the Global grid.

The following is written from memory and untested:

import iris

# load data
global_cube = iris.load_cube('global_data.nc')
uk_cube = iris.load_cube('uk_data.nc')

# subset global cube so that it only contains data in the UK area of interest
global_subset = global_cube.intersection(longitude=(-2, 5), latitude=(-50, 60))

result = uk_cube.regrid(global_subset, iris.analysis.Linear)