MITgcm global_ocean.90x40x15 (tutorial_global_oce_latlon) example snapshot — for xgcm grid-metrics examples

A small example dataset used by the xgcm Grid Metrics documentation. It is a single monthly-mean snapshot from the standard MITgcm verification/tutorial experiment tutorial_global_oce_latlon (a.k.a. global_ocean.90x40x15): a 4°×4° global latitude–longitude ocean configuration on an Arakawa C-grid, 90×40 horizontal points and 15 vertical levels. The MITgcm MDS binary output was wrapped into netCDF via xmitgcm.open_mdsdataset(..., geometry='sphericalpolar'). The file is byte-for-byte identical to datasets/mitgcm_example_dataset_v2.nc as historically shipped in the xgcm repository (md5 3176deb0b4d556d2981dff03ba2ed624); see the exact source blob on GitHub. It is provided so the documentation example can fetch the data via pooch rather than vendoring a binary in the repository.