added degrees units (#390)

* added degrees units

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* added test

* pre-commit

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Deepak Cherian <[email protected]>

Author: 3 people

cf_xarray/tests/test_units.py

@@ -31,6 +31,8 @@ def test_added_degrees_units():
     assert ureg("degrees_east") == ureg("degrees")
     assert ureg("degrees_east").to_base_units().units == ureg.radian
 
+    assert ureg("degrees").to_base_units().units == ureg.radian
+
 
 def test_gpm_unit():
     """Test that the gpm unit does alias to meters."""

cf_xarray/units.py

@@ -99,6 +99,8 @@ def repl(m):
 units.define(
     "degrees_east = degree = degrees_east = degrees_E = degreesE = degree_east = degree_E = degreeE"
 )
+# degrees for grid_longitude / grid_latitude for grid_mappings
+units.define("degrees = degree = degrees")
 units.define("[speed] = [length] / [time]")
 # ----- end block copied from xclim