Run SVD on ERA5

[dsj976]

Preliminary data analysis by doing SVD/POD of ERA5:

• [ ] Try running standard SVD on one year of ERA5 (numpy.linalg.svd)
• [ ] If that doesn't work, try running HPC-enhanced SVD

[ots22]

Update: we are using https://github.com/climetrend/pyloworder (forked from https://github.com/ArnauMiro/pyLowOrder) and have seen good parallel performance for SVD on some example data.