Wetting and drying in z* coordinates - bad idea?

[kshedstrom]

For historical reasons, our regional domains started with the z* vertical coordinate. Most have continued using z* because the OBCs work better that way. We now have a Gulf of Alaska domain in which we would eventually like to have wetting and drying. Both Cook Inlet and the Copper River delta have tidal mud flats. Setting the MASKING_DEPTH to -20 and MINIMUM_DEPTH to -10 causes the model to blow up:

FATAL from PE    42: MOM_regridding: adjust_interface_motion() - implied h<0 is larger than roundoff!

Trying again with MASKING_DEPTH = 0 and MINIMUM_DEPTH = 1 allows it to run. Does it make sense to have these values match? Am I setting them wrong or is z* the problem?

[kshedstrom]

Another thing about very shallow depths is that ice can form there, inducing brine rejection and this failure:

FATAL from PE     4: There were a total of         4 locations detected with extreme surface values!

WARNING from PE    34: Extreme surface sfc_state detected: i= 242 j= 187 lon=-144.672 lat=  60.196 x=-136.064 y=  55.549 D= 1.0000E-10 SSH= 1.5298E-03 SST=-3.1641E+00 SSS= 5.8595E+01 U-=-8.1887E-09 U+= 0.0000E+00 V-=-1.4694E-07 V+=-3.6210E-08

Perhaps this belongs in SIS2?

[kshedstrom]

It's the ALE remapping that has trouble with the dry beach cells. There are no target depths climbing up onto the mud flats.