Large-scale vertical velocity forcing (forc_wa) in casegen

[hertneky]

It seems that while forc_wa is intended to be active, the associated vertical velocity is not being read from the UFS history files and is consequently set to zero.

In my recent SFS work with casegen using zero wa(dzdt) forcing, I found the SCM results to be unsatisfactory compared to UFS simulation, particularly in simulating tropical precipitation over the Indian Ocean. To address this, I conducted a comparative experiment where I reintroduced proper wa forcing during case generation. The results indicated a notable improvement (in my subjective assessment) in precipitation simulations for both hydrostatic and nonhydrostatic scenarios within the SFS project. For hydrostatic cases, I utilized forc_wap since there is no wa (dzdt), but utilized wap (omga) output from the hydrostatic runs.

[grantfirl]

I'm confused by this issue. For forcing methods 1 and 3, no vertical velocity is necessary because for method 1, you already have the advective tendencies from the dycore (w has already acted on the tendencies from the dycore) and for method 3, you're using the total time tendencies of the state variables where vertical advection is already taken into account. The only forcing method where one needs a vertical velocity is for forcing method 2, and, as far as I can see, 'dzdt' is being read in and smoothed before written out to the forcing file.

Is the problem that dzdt is 0 in hydrostatic UFS runs?

[hertneky]

@grantfirl I need to remove this. Man asked me to close it since she discussed with the team exactly what you're saying here. @mzhangw Do you have any comment about dzdt being zero in hydrostatic runs?