Regridding library

This library file contains one function:

to_analysis_grid:

THe ML GCM operates on data with a single standard grid: pole at 90N, 180E, 79 latitude values and 158 longitude values. This has the UK nicely centred and a convenient grid size for strided convolutions. This function converts any iris cube onto this grid.

# Functions for regridding data

# The 20CRv2c grid has the UK on the grid boundary - I want it in the middle.
# Also we need grid dimensions that match strided conviolutions nicely.

# So adopt a standard analysis grid - equirectangular, with pole at
#  lat 90, lon, 180, and grid size of 79x158.

import iris
import numpy

# Regrid an iris cube onto the standard analysis grid 
def to_analysis_grid(cbe):
    # Standard pole with UK at centre
    cs=iris.coord_systems.RotatedGeogCS(90.0,180.0,0.0)
    # Latitudes cover -90 to 90 with 79 values
    lat_values=numpy.arange(-90,91,180/78)
    latitude = iris.coords.DimCoord(lat_values,
                                    standard_name='latitude',
                                    units='degrees_north',
                                    coord_system=cs)
    # Longitudes cover -180 to 180 with 159 values
    lon_values=numpy.arange(-180,181,360/158)
    longitude = iris.coords.DimCoord(lon_values,
                                     standard_name='longitude',
                                     units='degrees_east',
                                     coord_system=cs)
    dummy_data = numpy.zeros((len(lat_values), len(lon_values)))
    dummy_cube = iris.cube.Cube(dummy_data,
                               dim_coords_and_dims=[(latitude, 0),
                                                    (longitude, 1)])
    n_cube=cbe.regrid(dummy_cube,iris.analysis.Linear())
    return(n_cube)