Step-by-step guide
If you already know the desired resolution, one way to do this is through the GRIB Filter icon. This allows you to change the resolution and area of a GRIB field - see this tutorial for an example.
Since version 5.10, Metview has an advanced regridding module called Regrid. This has a mode that allows a template GRIB to be used to define the output grid. The following Python example shows the retrieval of a temperature field on one grid resolution and a subarea, and a land-sea mask on another grid; the land-sea mask is then put onto the same grid and subarea as the temperature field.
import metview as mv
t = mv.retrieve(param='t', grid=[0.5, 0.5], area=[50, 10, 80, 40])
lsm = mv.retrieve(param='lsm', levtype='sfc', grid=[0.2, 0.2])
regridded_lsm = mv.regrid(data=lsm,
grid_definition_mode='template',
template_data=t)