Split 4D-Var Mixed Resolution: Analysis phase

[hga007]

Description

This PR updates the split 4D-Var scheme to allow mixed-resolution applications. The background and analysis phases are run at a higher resolution (double, if decimation) than the increment phase (inner loops) doing the minimization.

• It forces the decimated NLM trajectory to be written with the standard NetCDF library. This is not possible with the PIO option. Thus, having both standard and PIO files in the background phase is possible.

Issue(s) addressed

Avoid using Matlab script to interpolate coarser increments to the background and analysis resolution.

Checklist

• I have reviewed code updates or enhancements described in this PR
• I have run and tested the changes before creating the PR