pkg/frazil/frazil_description.tex

e0b3e1bdd8 Dimi*0001 %%
                0002 %%
                0003
2b617e1849 Dimi*0004 Package ``FRAZIL'' is a repackaging and a replacement for subroutine
dd787e62fc Dimi*0005 freeze_interior.F and for run-time option allowInteriorFreezing, which has
2b617e1849 Dimi*0006 been retired.  It is meant to represent the formation of frazil at depth due
                0007 to pressure and freshening-related supercooling.
e0b3e1bdd8 Dimi*0008
2b617e1849 Dimi*0009 The initial functionality of pkg/frazil is similar to that previously provided
dd787e62fc Dimi*0010 by freeze_interior.F, that is, it checks for water below the freezing point at
38301bb7a2 Dimi*0011 depth and brings the negative heat anomaly to the surface level in one time
                0012 step.  Specifically, pkg/frazil currently assumes that: (i) supercooling at
                0013 depth creates frazil, which rises to the model's surface level in one model
                0014 time step, (ii) the frazil column operates at sub-grid scale and rises to the
                0015 surface through levels warmer than freezing point without melting, and (iii)
                0016 the frazil is porous to salinity as it rises through the water column, that
                0017 is, frazil does not generate or transport salt anomalies.  All these
                0018 assumptions can be relaxed at a later time as the package matures.
e0b3e1bdd8 Dimi*0019
dd787e62fc Dimi*0020 The difference with freeze_interior.F is that rather than directly change
2b617e1849 Dimi*0021 potential temperature THETA, pkg/frazil instead stores the required
610e3cd50d Dimi*0022 adjustments in a frazil temperature forcing matrix:
33e5e9881a Dimi*0023 FrazilForcingT (> 0 increases theta [W/m^2]).
e0b3e1bdd8 Dimi*0024
33e5e9881a Dimi*0025 The frazil forcing terms are computed prior to any of the ``ice'' packages and
38301bb7a2 Dimi*0026 routines (that is, seaice, thsice, shelfice, icefront, and freeze_surface).
                0027 This allows the ice packages to operate on FrazilForcingT directly (rather
                0028 than react to SST below the freezing point), if they need to do so, that is
                0029 they can operate on FrazilForcingT and decrease (or increase) it prior to
                0030 applying this FrazilForcingT to THETA in external_forcing.F
e0b3e1bdd8 Dimi*0031
2b617e1849 Dimi*0032 Package frazil is enabled with CPP option ALLOW_FRAZIL and runtime parameter
33e5e9881a Dimi*0033 useFRAZIL, in the usual MITgcm ways.  There are currently no pkg/frazil
                0034 runtime options, so there is no need for data.frazil runtime option file.