[MITgcm-support] Model crashing due to vertical velocities

[Andrea Cimatoribus]

Hi everybody,
I'm doing some tests with a 2D model (1 grid cell in the x direction, 1000 in the y direction, non hydrostatic). The resolution goes from approximately 700m to 7km, in the vertical it's from 10m to 40m (the low vertical resolution is to try to keep computational cost low). Just to start, I have no forcing, and an initial stable stratification in temperature (salt is constant).
The model is crashing due to very strong vertical velocities that develop close to the north/south boundaries. I did lots of testing with different values for viscosity and timestep (down to 1s), with no success. Anyway, if I change the bathimetry from flat bottom (3000m) to a sufficiently gentle slope, the model runs with no problem. I attach my data file. Any idea of what I'm missing? Could it be connected with the low resolution in the vertical? Before flooding you with figures from the model, I'd like to know if there's something simple that I'm missing.
Thanks a lot,
AC


# ====================
# | Model parameters |
# ====================
#
# Continuous equation parameters
&PARM01
tRef= 20.0, 19.7, 19.4, 19.1, 18.8, 18.4, 18.0, 17.7,
17.3, 16.9, 16.5, 16.0, 15.6, 15.2, 14.8, 14.3,
13.8, 13.4, 13.0, 12.6, 12.2, 11.7, 11.3, 11.0,
10.6, 10.1, 9.7, 9.3, 8.9, 8.6, 8.2, 8.0,
7.7, 7.5, 7.2, 7.0, 6.9, 6.7, 6.6, 6.4,
6.3, 6.2, 6.1, 6.0, 5.9, 5.8, 5.7, 5.68,
5.6, 5.56, 5.5, 5.47, 5.43, 5.39, 5.36, 5.32,
5.30, 5.27, 5.25, 5.22, 5.21, 5.19, 5.17, 5.16,
5.14, 5.13, 5.12, 5.11, 5.10, 5.09, 5.08, 5.07,
5.06, 5.05, 5.04, 5.04, 5.04, 5.03, 5.02, 5.01,
sRef=80*30.,
viscAh=12,
viscAz=3.E-1,
momViscosity=.TRUE.,
no_slip_sides=.TRUE.,
no_slip_bottom=.TRUE.,
diffKhT=1.E-1,
diffKzT=1.E-1,
# diffK4T=1.E-3,
# diffK4S=1.E-3,
f0=0.E-4,
beta=0.E-11,
tAlpha=2.0E-4,
sBeta =7.4E-4,
gravity=10.,
rhoConst=1030.,
rhoNil=1030.,
heatCapacity_Cp=4000.,
#rigidLid=.TRUE.,
implicitFreeSurface=.TRUE.,
# exactConserv=.TRUE.,
eosType='LINEAR',
nonHydrostatic=.TRUE.,
# implicitDiffusion=.TRUE.,
tempAdvection=.TRUE.,
tempDiffusion=.TRUE.,
tempForcing=.FALSE.,
saltStepping=.TRUE.,
saltAdvection=.TRUE.,
saltDiffusion=.TRUE.,
saltForcing=.FALSE.,
tempAdvScheme=33,
# saltAdvScheme=33,
staggerTimeStep=.TRUE.,
&

# Elliptic solver parameters
&PARM02
cg2dMaxIters=1000,
cg2dTargetResidual=1.E-9,
cg3dMaxIters=100,
cg3dTargetResidual=1.E-9,
&

# Time stepping parameters
&PARM03
nIter0=0,
endTime=86400.,
#nTimeSteps=3,
deltaT=10.,
pChkptFreq=86400.,
chkptFreq=86400.,
dumpFreq=30.,
monitorFreq=1800.,
monitorSelect=1800,
tauSaltClimRelax = 864000.,
tauThetaClimRelax = 864000.,
&

# Gridding parameters
&PARM04
usingCartesianGrid=.TRUE.,
dXspacing=1000.,
# dYspacing=5000.,
delZ=5*10.,5*15.,5*20.,5*25,5*30,55*46
delYfile = 'delY.bin',
&

# Input datasets
&PARM05
thetaClimFile = 'SurfTemp.bin',
saltClimFile = 'SurfSalt.bin',
bathyFile = 'bathy.bin',
&