Surface Data Assmilation with GSI

Hello everybody!

Trying to do Surface Data Assimilation only (not upper air Data Assimilation) with GSI. This is assimilate screen level obs (u/v10m, T/RH2m, SfcPress, Z0) to update soil/surface fields. I can do this with HARMONIE-AROME model (IFS/ARPEGE based), because SurfaceDA and UpperAirDA are separate tasks. I have been reading the GSI user guide but I have not found how to do this. Does anyone know if this is possible? And if so, where should I start looking at?

Thanks in advance!

Pau Escribà

Spanish Met Agency (AEMET)