Reading GDAS Ensemble directly for HAFS-JEDI

[XuLu-NOAA]

This is to document the progress of such efforts.

The GDAS ensemble file we have are in Gaussian grid. However, discussion with Dan indicates that JEDI cannot handle the Gaussian grid read in. So we can not directly use the other geometry approach from the dual-resolution DA.

To begin with, IO/StructuredGrid/IOStructuredGrid already has the function to interpolate from FV3 model grid to Gaussian grid.
So we need to reverse-engineer the code to read in Gaussian and interpolate back to the model grid within altas.
Working with AI on this read in step.