Reprojection of ECMWF (ancillary data) GRIB on S2 bands grids

Is there an easy way to reproject (resample) the ECMWF GRIB file (provided in the L1C) onto the S2 band grids (10, 20 or 60 m) with snappy?
Thanks a lot,

You could first resample the s2 product to the desired resolution.
Afterwards you have two options.
You can use the Collocate operator and specify the resampled S2 product as master and the ECMWF data as slave. The result will be a single product containing data from both products.
Or you can use Reproject operator and use the parameter and specify the collocateWith source product parameter. The ECMWF data would be the normal source product and the S2 the collocateWith product.
This will reproject the ECMWF onto the S2 grid.

Thanks for your prompt reply.
I think there is no reader for GRIB files in snappy, isn’t it?

That’s true. The Grib files are not supported. But the NetCDF files should work.