Basic conversion operators #1852
Description
What problem does your feature request solve?
Sometimes we will need to convert between different variables (e.g. mixing ratio and specific humidity) but will only have a different output and so we will need to convert to the required output. A set of operators that can do this would be beneficial as setting a standard, and consistent approach in CSET.
Describe the solution you'd like
The following operators are basic conversions not taking into account grid staggering or vertical level differences (see #1863).
A set of conversion operators for different humidity variables to be stored under `humidity.py:
- specific humidity to mixing ratio
- mixing ratio to specific humidity
- specific humidity to relative humidity
- mixing ratio to relative humidity
- relative humidity to specific humidity
- relative humidity to mixing ratio
A set of derived temperature operators in 'temperature.py':
- Virtual temperature
- Dewpoint temperature
- Potential temperature
- Equivalent Potential temperature
- Virtual temperature
- Virtual potential temperature
- Saturation potential temperature
A set of derived pressure operators in 'pressure.py':
- Vapour pressure
- Saturation vapour pressure
Describe alternatives you've considered
Use of Metpy could be an option, however it is less efficient with model data. Furthermore, with different model levels, and grid staggering we need to ensure consistent and appropriate handling within these operators where required.