Feature request: JEDI forward operators for use in DART

[hkershaw-brown]

Use case

This has already been accomplished by people (most notably Craig Schwartz) 🎉

Is your feature request related to a problem?

Related to #724, precomputed (external forward operators) are used with DART, but not documented or available though NCAR/DART repo.
Note: ROMS observation converter does provide forward operators. We have users using RTTOV external forward operators.

Describe your preferred solution

• Implantation though the current external forward operator mechanism (obs_sequence files). This is what is out there and what people have been using.
• JEDI obs to obs_seqence (no fwd op) so DART can ingest JEDI IODA observations.

Describe any alternatives you have considered

However, in the not too distant future (maybe a subsequent issue to this JEDI v1 issue, or maybe concurrent since this is not JEDI specific)

• Memory scalable (and IO parallel) version of external forward operators.

[hkershaw-brown]

Have some IODA obs (compo) on Derecho, & code from Craig.
/glade/work/hkershaw/DART/JEDI