Add Azimuthal Averaging

[jpan84]

Closes #1254

Compute azimuthal mean in radial rings around a central point.

Overview

Like uxarray.UxDataArray.zonal_mean(), this aggregates over faces to output the data with a new horizontal dimension radius. Following uxarray.UxDataArray.subset.bounding_circle, this function uses ball_tree.query_radius to select grid elements in a circular neighborhood from one center coordinate. For radii r=[r1, r2, r3, ...], face centers at distance d (given in great-circle degrees), where r2<d<=r3 will be used for the azimuthal mean at r3.

This is one solution for issue #1254

This may be tangentially relevant to issue #930.

Expected Usage

import uxarray as ux
import matplotlib.pyplot as plt

grid_path = '/glade/p/cesmdata/inputdata/share/scripgrids/ne120np4_pentagons_100310.nc'
data_path = '/glade/work/jpan/azim_test_data.nc'

uxds = ux.open_dataset(grid_path, data_path)
uxda = uxds['OMEGA500']
print(uxda)

azim_mean, hit_count = uxda.azimuthal_mean((183., -18.933), 5, 0.3)

print(azim_mean)
print(hit_count)
plt.plot(azim_mean.radius, azim_mean.isel(time=0))
plt.show()

PR Checklist

General

• [✓] An issue is linked created and linked
• Add appropriate labels
• [✓] Filled out Overview and Expected Usage (if applicable) sections

Testing

• Adequate tests are created if there is new functionality
• Tests cover all possible logical paths in your function
• Tests are not too basic (such as simply calling a function and nothing else)

Documentation

• [✓ ] Docstrings have been added to all new functions
• [N/A ] Docstrings have updated with any function changes
• [N/A] Internal functions have a preceding underscore (_) and have been added to docs/internal_api/index.rst
• User functions have been added to docs/user_api/index.rst

Examples

• Any new notebook examples added to docs/examples/ folder
• Clear the output of all cells before committing
• New notebook files added to docs/examples.rst toctree
• New notebook files added to new entry in docs/gallery.yml with appropriate thumbnail photo in docs/_static/thumbnails/