Regridding produces wrong chunktype for lazy masked arrays #5988
Description
🐛 Bug Report
Regridding sets the chunktype to numpy.ndarray when it should be numpy.MaskedArray. This can result in ignoring the mask when subsequently using iris.cube.Cube.rolling_window.
How To Reproduce
Steps to reproduce the behaviour:
import iris
import dask.array as da
global_air_temp = iris.load_cube(iris.sample_data_path('air_temp.pp'))
rotated_psl = iris.load_cube(iris.sample_data_path('rotated_pole.nc'))
global_air_temp.data = da.ma.masked_array(global_air_temp.core_data())
print(global_air_temp.core_data())
# prints dask.array<masked_array, shape=(73, 96), dtype=float32, chunksize=(73, 96), chunktype=numpy.MaskedArray>
rotated_air_temp = global_air_temp.regrid(rotated_psl, iris.analysis.Linear())
print(rotated_air_temp.core_data())
# prints dask.array<_regrid, shape=(22, 36), dtype=float32, chunksize=(22, 36), chunktype=numpy.ndarray>Expected behaviour
I would expect the second print statement above to produce
dask.array<_regrid, shape=(22, 36), dtype=float32, chunksize=(22, 36), chunktype=numpy.MaskedArray>
Environment
- OS & Version: Ubuntu 23.10
- Iris Version: 3.9