For now, atmospheric nudging can be used only for experiments run at ECMWF, as the reference data for nudging is stored on ECFS under the following path: ec:/c3l/reffiles/b0ir/
For the time being, branches are designed for use at ECMWF, with b0ir reference data copied in the local $SCRATCH folder of the HPC to avoid a high number of accesses to the ECFS file storage system. The template branch is develop-AtmNudging, and model branch is develop-v3.0.1_AtmNudging. Both are updated to Autosubmit 2.2 (minor changes should be done to adapt to the new structure for Autosubmit 2.3).
In the expdef.conf file for the experiment, you can set the strength of the nudging by defining the alpha parameter: alpha ranges from 0 to infinity and is defined so that:
Xnudged = (X + alpha * Xref)/(1 + alpha)
If alpha is equal to one, the nudged field is midway between the original model value before nudging and the reference field value.
Some changes should be made to the sim template of the run to adapt to other users running atmospheric nudging. Please e-mail me (lauriane.batte[AT]meteo.fr) for more details.