[MITgcm-support] Overestimation of Global SST and SSS

[Abhisek Chakraborty]

Dear All,

I have configured MITgcm for global oceans (80S-80N, 0-360deg, 32 vertical
levels, 1*1 deg horizontal resolution) and ran it for 100 years using
climatological forcings. After completing the run,  when I compared the
simulated values (e.g. SST and SSS) with Levitus climatology, I found a
huge overestimation by the model. The 'data' file I used for my simulation
is:

# ******************************
# Model parameters
# Continuous equation parameters
# ******************************
 &PARM01
 tRef= 25.0,24.5,24.0 , 23.5, 23.0 ,22.5, 22.0 , 21.5,21.0 ,20.5, 20.0 ,
       19.5, 19.0 , 18.5, 18.0 ,17.5, 17.0 , 16.0 , 15.0 ,
       14.0 , 13.0 , 12.0 , 11.0 , 10.0 ,
        9.0 ,  8.0 ,  7.0 ,  6.0,   5.0 ,
        4.0 ,  3.0 ,  2.0 ,
 sRef=34.58, 34.62, 34.68, 34.72, 34.73,
       34.65, 34.75, 34.82, 34.87, 34.90,
       34.90, 34.86, 34.78, 34.69, 34.60,
       34.58, 34.62, 34.68, 34.72, 34.73,
       34.74, 34.73, 34.73, 34.72, 34.72,
       34.71, 34.70, 34.69,34.78, 34.69, 34.60,34.72,
 no_slip_sides=.false.,
 no_slip_bottom=.TRUE.,
 viscAr=1.E-4,
 viscAh=1.E2,
 diffKhT=0.0,
 diffKrT=3.E-5,
 diffKhS=0.0,
 diffKrS=3.E-5,
 rhonil=1035.,
 rhoConstFresh=1000.,
 beta=1.E-11,
 tAlpha=2.E-4,
 sBeta =7.4E-4,
 gravity=9.81,
 gBaro=9.81,
 rigidLid=.FALSE.,
 implicitFreeSurface=.true.,
 eosType='JMD95Z',
 ivdc_kappa=100.,
 implicitDiffusion=.TRUE.,
 allowFreezing=.TRUE.,
 exactConserv=.TRUE.,
 useRealFreshWaterFlux=.TRUE.,
 useCDscheme=.TRUE.,
 readBinaryPrec=32,
 writeBinaryPrec=32,
 hFacMin=0.05,
 hFacMinDr = 50,
 useSingleCpuIO =.TRUE.,
 globalFiles = .TRUE.,
 &

# **************************
# Elliptic solver parameters
# **************************
 &PARM02
 cg2dMaxIters=500,
 cg2dTargetResidual=1.E-13,
 &

# ************************
 Time stepping parameters
# ************************
 &PARM03
# nIter0=      18000,
# nTimeSteps = 27000,
# 100 years of integration will yield a reasonable flow field
 startTime = 0.,
 endTime   = 3110400000.,
 deltaTmom = 100.,
 tauCD =     321428.,
 deltaTtracer= 43200.,
 deltaTClock = 86400.,
 deltaTfreesurf= 172800.,
 abEps = 0.1,
 pChkptFreq= 2592000.,
 dumpFreq=   2592000.,
 taveFreq=   2592000.,
 monitorFreq=2592000.,
# 2 months restoring timescale for temperature
 tauThetaClimRelax= 5184000.,
# 6 months restoring timescale for salinity
 tauSaltClimRelax = 15552000.,
 periodicExternalForcing=.TRUE.,
 externForcingPeriod=2592000.,
 externForcingCycle=31104000.,
 &

# Gridding parameters
 &PARM04
 usingSphericalPolarGrid=.TRUE.,
 delR= 10.,10.,20., 25.,25.,25.,25.,50.,50.,
       50.,100.,100.,100.,100.,100.,100.,100.,100.,100.,100.,
       100.,100.,250.,250.,500.,500.,500.,500.,500.,500.,500.,500.,
ygOrigin=-80.,
xgOrigin=0.0,
dySpacing=1.,
dxSpacing=1.,
&

# Input datasets
 &PARM05
 bathyFile=      'ETOPO2.BIN',
 hydrogThetaFile='LEV_T.BIN',
 hydrogSaltFile= 'LEV_S.BIN',
 zonalWindFile=  'TAUX.BIN',
 meridWindFile=  'TAUY.BIN',
 thetaClimFile=  'SST.BIN',
 saltClimFile=   'SSS.BIN',
 surfQFile=      'QNET.BIN',
 the_run_name=   'global_oce_latlon',
# fresh water flux is turned on, comment next line to it turn off
# (maybe better with surface salinity restoring)
  EmPmRFile=      'EMP.BIN',
&

The 'packages.conf' files is
#
#  $Header:
/u/gcmpack/MITgcm/verification/tutorial_global_oce_latlon/code/packages.conf,v
1.3 2009/06/29 01:58:27 jmc Exp $
#  $Name: checkpoint63m $
#

gfd
gmredi
cd_code
timeave
ptracers
mnc

The MONTHLY PLOTS of simulation and corresponding LEVITUS values are
attached here for 12 months (after 100years). Also the PLOT of time
averaged Kinetic Energy is attached. (Attachment is made with WINRAR).

Can anyone please look into the attached results and guide me to correct my
simulations?


Thanking in advance,
Abhisek Chakraborty
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