Step-by-step guide
Let's say you want your message to use the product definition template 40 (The full list is defined in Code table 4.0):
% grib_set -s productDefinitionTemplateNumber=40 input.grib2 output.grib2
Now you can do a "grib_dump -O" to inspect the section 4 (Product definition section) of the output.grib2 file to see the new key "constituentType" (For other templates you will see other keys added).
Of course you can also set any key which belongs to this product via this command. Let's say we want the new product as well as the Ozone constituent type:
% grib_set -s productDefinitionTemplateNumber=40,constituentType=1 input.grib2 output.grib2
Here we've done two things in one command:
- First choose the right product template. This will give birth to the key "constituentType".
- Then change the constituent type from the default (0) to 1 (=Ozone)
So the order of keys being set is important.