Resize GRIB2 file

[Bap250]

Hello !

I am a novice in computer science applied to meteorology.
I want to extract data from a GRIB2 file. I need to resize the files because I am downloading raw data from a global weather forecast model (ICON) and I just need a small footprint of the model. So I need to create a new GRIB2 file less heavy in storage with just the span I am interested in, that is France.

I saw that it was possible to use the "pygrib" package.
But I tried to write the script but it doesn't work.

The output GRIB2 file can't be opened on any software that processes GRIB2 data. I even have the impression that it does not resize. It just separated the timelines from the original grib2 file.

Below is the script I wrote in python language. Sorry for the formatting ! I don't know how to add code with a nice layout 👍 😎 !

Can anyone help me?

I thank you in advance for your help.
Bap250

import pygrib

grbs = pygrib.open('originalfile.grib2')
grbs.seek(2)
grbs.tell()
grb = grbs.read(1)[0]
grbs.tell()

grb = grbs.select(name='Total Precipitation')[0].data(lat1 = 43, lat2 = 51, lon1 = -4, lon2 = 8)

print(grb)

grbs.close()

grbout = open('outfile.grib2', 'wb')
grbout.write(grb[0])
grbout.close()`

[jswhit]

you need a template file that is the same domain as the one you want to save, and then you can overwrite the data and change the metadata. Unfortunately, pygrib cannot create a grib2 file from scratch.