Dimensionless and other strange unit conversion

[mandresm]

Problem

Some units in the CMOR tables are listed as 0.001 or 1. At the same time, the model output also have similar units. These units typically correspond to dimensionless units for example for the salinity the unit in the CMOR tables is 0.001 which really means in pyhical terms g/Kg (dimensionless).

The problem is that if we want to achieve an automatic conversion of units we need to tell our tool what these 0.001 unit means physically (g/kg) (i.e. what is it's physical quantity), and that might vary from variable to variable.

Proposed solution

On the model side

Specify the "physical" unit in the rule of the input yaml file:

- rule:
    unit: g/kg

On the CMOR tables side

Yaml file that is part of Pymorize repo, co-develop with the power users

sst:
    "0.001": g/kg

This mapping can then be use to make pymorize and pint "understand" what the CMOR table means by 0.001

TODOS

• [ ]

[pgierz]

Recommendation to keep this easily configurable. In the main user-yaml, add a key/value for dimensionless_mapping_table: <some/path/to/a/file>, e.g. in examples/sample.yaml

general:
    .... metadata relevant for humans
pymorize:
  # parallel: True
  warn_on_no_rule: False
  use_flox: True
  cluster_mode: fixed
  fixed_jobs: 12
  # minimum_jobs: 8
  # maximum_jobs: 30
+ dimensionless_mapping_table: data/pymorize/dimensionless_mappings.yaml

[pgierz]

Work on implementation in #55

[mandresm]

Work on implementation in #55

Thanks @pgierz!