This Python script will allow you to compute the geopotential on each model level.

• Based on code from Nils Wedi, the IFS documentation:
  • CY41R1 Official IFS Documentation
    • part III. Dynamics and numerical procedures

For this use case, you need to retrieve in grib format both temperature (t) and Specific humidity (q) for each model level. Besides, you need both geopotential (z) and logarithm of surface pressure (lnsp) for model level = 1.