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Understanding Obsgrid

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New member
I am trying to better understand what Obsgrid is doing and how it can affect my WRF simulation.

I have been replacing the metgrid "met_em" files with the Obsgrid output "metoa*" files. What does this do exactly? Is it considered the Objective analysis? See below from the WRF user guide:

"OBSGRID has the capability to perform the objective analysis on a nest. This is done manually with a separate OBSGRID process, performed on met_em_d0x files for the particular nest. Often, however, such a step is unnecessary; it complicates matters for the user and may introduce errors into the forecast. At other times, extra information available to the user, or extra detail that objective analysis may provide on a nest, makes objective analysis on a nest a good option."

Q: If I want to observationaly nudge WRF, am I supposed to also replace the 'met_em' files with the 'metoa' files in addition to the cat'ed OBS_DOMAINd01 file? Or is that step unnecessary?

Q: Is there any benefit to using ONLY the 'metoa' files and not observationally nudging the WRF simulation?