[MITgcm-support] instability at Eta

[kaveh Purkiani]

Hello everybody,

I have a configuration to simulate the circulation in tropical Pacific
Ocean. It is a simple box model with 20 grid cells in horizontal and
200 in vertical.

Daily averaged temp, salt, u and v velocities are downloaded from
HYCOM. As to OBCS, all the open boundary files are written as
Nx/y*Nz*time format
(here is 20*200*232).

Salinity, temperature, u and v outputs of the model at boundaries are
read correctly by the model. The CFL number (eq.3.28) is extremely
below the
criteria.

As simulation forwards, Eta decreases drastically until I get Nan
values and so negative values for temperature. How to solve this?


Besides that I am having another problem. Although the temperature and
salinity forcing seem to behave as they are, the forcing of the u and
v
velocities are not. In the NetCDF files I get, T and S of dimension 20
* 20, u of dimension 21 x 20 and v of dimension 20 x 21 which
make sense. Therefore, I have two columns of boundary values for U
values at western boundary, similar happens at eastern boundary.
The penultimate column is fine but the next one (last column) is
duplication of western boundary. Similar for V values at Northern and
Southern boundaries happen.
Does this cause an error in reading boundaries? If yes, how to solve
this. I already tried with different OLx and OLy but did not help.

Does anyone have any ideas about what could be my mistake?


below are my data, data.exf and data.obcs files:

# ====================
# | Model parameters |
# ====================
#
# Continuous equation parameters
 &PARM01
# tRef= 200*8,
# sRef= 200*34,
 implicitDiffusion=.TRUE.,
 implicitViscosity=.TRUE.,
 viscAr=1.E0,
 viscAh=1.E0,
#- put small value (<< stab.limit ~ 3.e10) only to test biharmonic-viscosity
 viscA4=1.E8,
 no_slip_sides=.FALSE.,
 no_slip_bottom=.FALSE.,
 diffKhT=1.E3,
 diffKrT=1.E-5,
 diffKhS=1.E3,
 diffKrS=1.E-5,
 saltAdvScheme=4,
 eosType='LINEAR',
 tAlpha=2.E-4,
 sBeta =0.E-4,
 gravity=9.81,
 f0=1.e-4,
 beta=0.E-11,
 nonHydrostatic=.FALSE.,
 rigidLid=.FALSE.,
 implicitFreeSurface=.TRUE.,
 exactConserv=.TRUE.,
 hFacMin=0.2,
 readBinaryPrec=64,
 nonlinFreeSurf = 4,
# hFacInf=0.0002,
# hFacSup=2.5,
 &

# Elliptic solver parameters
 &PARM02
 cg2dMaxIters=1000,
 cg2dTargetResidual=1.E-13,
 &

# Time stepping parameters
 &PARM03
 nIter0=0,
 nTimeSteps=288000,
 baseTime=0.,
 deltaT=10.0,
 abEps=0.1,
 momDissip_In_AB=.FALSE.,
 pChkptFreq=0.0,
 chkptFreq=0.0,
 dumpFreq=900.0,
 monitorSelect=2,
 monitorFreq=1.,
# for time dependent open boundary conditions, activate the following 3 lines:
# periodicExternalForcing=.FALSE.,
# externForcingPeriod=86400.,
# externForcingCycle =20044800.,
 &

# Gridding parameters
 &PARM04
 usingCartesianGrid=.FALSE.,
 usingSphericalPolarGrid=.TRUE.
 ygOrigin=24.5,
 xgOrigin=117.525,
 delX=20*0.01,
 delY=20*0.01,
 delR= 200*20,
 &

# Input datasets
 &PARM05
 bathyFile = 'topognew-nobump.bump',
 hydrogThetaFile='initial_temp.bin',
 hydrogSaltFile= 'initial_salt.bin',
&

data.exf:



# External Forcing Data
# *********************
 &EXF_NML_01
 exf_iprec         = 64,
 useExfCheckRange=.TRUE.,
 &
# *******************
 &EXF_NML_02
 &
# ***************
 &EXF_NML_03
 &
#
 &EXF_NML_04
 &
 &EXF_NML_OBCS
 obcsNstartdate1=20070101,
 obcsNstartdate2=000000,
 obcsNperiod=86400,
#
 obcsEstartdate1=20070101,
 obcsEstartdate2=000000,
 obcsEperiod=86400,
#
 obcsSstartdate1=20070101,
 obcsSstartdate2=000000,
 obcsSperiod=86400,
#
 obcsWstartdate1=20070101,
 obcsWstartdate2=000000,
 obcsWperiod=86400,
 &


data.obcs:


# Open-boundaries
 &OBCS_PARM01
# This flag turns off checking and fixing problematic topography across
# open boundaries.
 OBCSfixTopo=.TRUE.,
 OB_Jnorth= 20*-1,
 OB_Jsouth = 20*1,
 OB_Ieast = 20*-1,
 OB_Iwest = 20*1,
useOBCSprescribe = .TRUE.,
 OBNuFile  = 'OB_NorthU.bin',
 OBNvFile  = 'OB_NorthV.bin',
 OBNsFile  = 'OB_NorthS.bin',
 OBNtFile  = 'OB_NorthT.bin',
 OBSuFile  = 'OB_SouthU.bin',
 OBSvFile  = 'OB_SouthV.bin',
 OBSsFile  = 'OB_SouthS.bin',
 OBStFile  = 'OB_SouthT.bin',
 OBEuFile  = 'OB_EastU.bin',
 OBEvFile  = 'OB_EastV.bin',
 OBEsFile  = 'OB_EastS.bin',
 OBEtFile  = 'OB_EastT.bin',
 OBWuFile = 'OB_WestU.bin',
 OBWvFile = 'OB_WestV.bin',
 OBWsFile = 'OB_WestS.bin',
 OBWtFile = 'OB_WestT.bin',
&



Thank you very much for your attention in advance.

regards,

Kaveh.
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