More engineering fixes required for the CICE initialization

[guillaumevernieres]

Description

There are a few more cases for which the CICE model forecast becomes unstable.

Solution

Something needs to be done about snow enthalpy and small sea-ice concentration values.
Solution from Philip Pegion:

1. Removal of small sea-ice

import xarray as xr
import numpy as np
import sys
import shutil

infile=sys.argv[1]
ds_in=xr.open_dataset(infile)

var_list=['vicen','vsnon','Tsfcn','iage','alvl','vlvl', 'apnd', 'hpnd', 'ipnd',\
 'dhs', 'ffrac', 'sice001', 'qice001', 'sice002', 'qice002', 'sice003', 'qice003',\
 'sice004', 'qice004', 'sice005', 'qice005', 'sice006', 'qice006', 'sice007', 'qice007','qsno001','aicen']
for var in var_list:
    tmparr=np.where(ds_in['aicen'].values >0.15,ds_in[var],0.0)
    ds_in[var][:]=tmparr


new_frac=tmparr.sum(axis=0)
new_mask=np.where(new_frac > 0, 1.0,0.0)
ds_in['iceumask'][:]=new_mask
ds_in.to_netcdf('trimmed_'+infile)
ds_in.close()
shutil.move(infile,'old_'+infile)
shutil.move('trimmed_'+infile,infile)

2. Limit snow enthalpy

import xarray as xr
import numpy as np
import sys

infile=sys.argv[1]
anl=xr.open_dataset('anl_'+infile)
rhos      = 330.0
cp_ice    = 2106.
c1        = 1.0
Lsub      = 2.835e6
Lvap      = 2.501e6
Lfresh=Lsub - Lvap
rnslyr=1.0
puny=1.0E-012

# icepack formulate for snow temperature
A = c1 / (rhos * cp_ice)
B = Lfresh / cp_ice
zTsn = A * anl['qsno001'][:].values + B
# icepack formula for max snow tempature
Tmax = -anl['qsno001'][:].values*puny*rnslyr /(rhos*cp_ice*anl['vsnon'][:].values)

# enthlap at max now tempetarure
Qmax=rhos*cp_ice*(Tmax-Lfresh/cp_ice)

# fill in new enthalpy where snow temperature is too high
newq=np.where(zTsn <= Tmax,anl['qsno001'][:].values,Qmax)
newf=np.where(anl['vicen'] > 0.00001,anl['aicen'][:].values,0.0)

# fill in snow enthalpy (0) where there is no snow
newq2=np.where(anl['vsnon'][:]==0.0,anl['qsno001'][:].values,newq)
anl['qsno001'][:]=newq2
anl['aicen'][:]=newf
# write out file
anl.to_netcdf(infile)

The above features need to be added to the soca2cice var change.

[ShastriPaturi]

Thanks for sharing @guillaumevernieres