CDO

Hi,
I try to extract global radiation from dwd icon-d2 netcdf forcast files.
Later on I plan to use this data for photovoltaic yield prediction with pvlib.

pvlib needs
ghi: Global horizontal irradiance in W/m^2
dni: the direct normal irradiance in W/m^2
dhi: the diffuse horizontal irradiance in W/m^2

netcdf contains:
ASWDIFD_S Surface down solar diffuse radiation(average since model start)
ASWDIR_S Surface down solar direct radiation (average since model start)

My questions:
1) Is ghi the same as time averaged global radiation?

2) How can I extract and compute the ghi from netcdf file for hourly intervals with cdo?
The time averaged fields are derived in the following way:

[https://www.dwd.de/SharedDocs/downloads/DE/modelldokumentationen/nwv/icon/icon_dbbeschr_aktuell.pdf?view=nasPublication&nn=495490]

Any help is welcome

Danke und Grüße
Markus