Introduction

Some users are interested on the height of the different model levels. This Python script will allow you to compute the geopotential on each one. The starting point is the geopotential and the pressure (z and lnsp) on the surface.

The script is 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.

Download

Download Script

compute_geopotential_on_ml.py

Examples

python compute_geopotential_on_ml.py tq_ml_20151008_00.grib zlnsp_ml_20151008_00.grib
python compute_geopotential_on_ml.py tq_ml_20151008_00.grib zlnsp_ml_20151008_00.grib -o my_grib.grib

tq_ml_20151008_00.grib

retrieve, 
  date= 20150801, 
  class = od,
  time= 0, 
  stream = oper,
  levtype= ml, 
  grid= 1.5/1.5,
  type= an,
  param= t/q, 
  levelist= all,
  target="tq_ml_20150801_00.grib"

zlnsp_ml_20151008_00.grib

retrieve,
  date= 20150801, 
  class = od,
  time= 0, 
  stream = oper,
  levtype= ml, 
  grid= 1.5/1.5,
  type= an,
  param=lnsp,
  levelist=1,
  target="zlnsp_ml_20151008_00.grib"

retrieve,
  type= an,
  param=z, 
  levelist=1,
  target="zlnsp_ml_20151008_00.grib"