R21 HISTORY: landice, land, ocean

[gmao-rreichle]

A few things related to R21C file specs did not get done in #356:

1. Add land surface constants output as in MERRA-2: const_2d_lnd_Nx (M2CONXLND) "Constant Land‐Surface Parameters". I think in MERRA-2, this was done manually (by Rob and Qing working with matlab). It would be preferable to have this formalized through HISTORY, if at all possible. Needs thought.

2. Suggested ocean forcing output from @sanAkel: R21C HISTORY output specs (precip, land, landice, ...) #356 (comment)
   See also R21C HISTORY output specs (precip, land, landice, ...) #356 (comment)
   Not needed anymore.

3. EVAP and EVAPOUT decision still pending? R21C HISTORY output specs (precip, land, landice, ...) #356 (comment)

4. The changes in R21C HISTORY output specs (precip, land, landice, ...) #356 need to find their way into the GCM App develop branch so they will eventually find their way into all GMAO systems. For "lnd", when merging with 'develop', make sure not to inadvertently drop the new "PEATCLSM" output variables.

cc: @elakkraoui @lcandre2 @lltakacs @sdrabenh @rcullath @rlucches