The documentation (or this diagram) on interpolation with MIR shows output grids as starting with a SH representation, then if RESOL = AV (“Archived Value”), translation to e.g. an O320 grid as an intermediate. What is the AV grid? Is data actually stored here rather than in SH coefficients?
For example, if I download the extended range hindcasts with “grid=av”, then I get a regular grid that looks like O320 in latitude, but has the same number of longitude points as 0320 does on the equator. So it’s denser than N320.