Enable WW3 diagnostics via coupler

[alperaltuntas]

This PR introduces the following wave import fields for coupler (CMEPS) to write out history files:

• HS (significant wave height)
• T01, T0M1 (mean wave periods)
• THM (mean wave direction)

testing: aux_ww3 (beta07). status: b4b

to be evaluated in conjunction with: ESCOMP/CMEPS#621

[DeniseWorthen]

@alperaltuntas I saw your related CMEPS PR. It looks like you're not updating from dev/ufs-weather-model anymore, but these fields have already been added as export variables (they were needed by the coastal configurations).

If you simply grab the value of these variables from w3adatmd, you will get variables that have only been calculated on the wave model's history frequency since the call to w3outg (which calculates the values) is only made on that frequency. The way it is implemented in dev/ufs-weather-model is that they are calculated at the actual export frequency. It may not matter for your purposes (and you may realize it anyway), but I thought I would mention it.

[alperaltuntas]

@alperaltuntas I saw your related CMEPS PR. It looks like you're not updating from dev/ufs-weather-model anymore, but these fields have already been added as export variables (they were needed by the coastal configurations).

If you simply grab the value of these variables from w3adatmd, you will get variables that have only been calculated on the wave model's history frequency since the call to w3outg (which calculates the values) is only made on that frequency. The way it is implemented in dev/ufs-weather-model is that they are calculated at the actual export frequency. It may not matter for your purposes (and you may realize it anyway), but I thought I would mention it.

@DeniseWorthen Right, in our case, w3outg gets called every coupling timestep, but thanks so much for the heads up!