[MITgcm-support] Eta is fine,but velocity is too large

[Chun-Yan Zhou]

Hi all,
 I want to simulate the tide in East China Sea, with open boundary at the East and South. I provide the Eta file as the boundary condition. The Eta result is fine, close to the real tidal height, however, the velocity is too large, even up to 13m/s, when the viscAh=1E2; the I change the visAh=1E4, the velocity became smaller, so did the Eta. I also change the bottomDragQuadratic from 0.003 to 0.0001, but didn't make the velocity smaller. Is there any parameter I could set to reduce the largest velocity while keep the Eta as it is?
 Any suggestion is highly appreciate!
 chunyan

 # ====================
# | Model parameters |
# ====================
#
# Continuous equation parameters
 &PARM01
 tRef=40*20.,
 viscAh=1.E2,
 viscAz=1.E-3,
 no_slip_sides=.TRUE.,
 no_slip_bottom=.TRUE.,
 bottomDragQuadratic=0.001,
 diffKhT=1.E2,
 diffKzT=1.E-3,
 diffKhS=0.E2,
 diffKzS=0.E-5,
 tAlpha=2.E-4,
 sBeta =0.,
 gravity=9.81,
 eosType='LINEAR',
 tempStepping=.FALSE.,
 implicSurfPress=0.5,
 implicDiv2DFlow=0.5,
 rigidLid=.FALSE.,
 implicitFreeSurface=.TRUE.,
 readBinaryPrec=64,
 writeBinaryPrec=64,
 hFacMin=0.05,
 nonlinFreeSurf=4,
 exactConserv=.TRUE.,
 &

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

# Time stepping parameters
 &PARM03
 nIter0=0,
 nTimeSteps=40000,
 deltaT=22.357,
 cAdjFreq=0.,
 abEps=0.02,
 pChkptFreq=447140,
 chkptFreq=0.0,
#dumpFreq=7200.0,
 dumpFreq=4471.4,
#taveFreq=86400.0,
 monitorFreq=3600.,
 periodicExternalForcing=.TRUE.,
 externForcingPeriod=223.57,
 externForcingCycle=2592070.58,
 pickupStrictlyMatch=.FALSE.,
 &

# Gridding parameters
 &PARM04

 usingSphericalPolarGrid=.TRUE.,
 delX=174*0.0625,
 delY=226*0.0625,
 delZ=10*3.,10*7.,10*25.,5*100.,5*180.,
 ygOrigin=27.03125,
 &

# Input datasets
 &PARM05
 bathyFile='topog.slope',
 &


# Open-boundaries
 &OBCS_PARM01
 OB_Ieast=226*-1,
 OB_Jsouth=174*1,
 useOBCSprescribe=.TRUE.,
 useOBCSsponge=.TRUE.,
 OBEetaFile = 'OBEeta.bin',
 OBSetaFile = 'OBSeta.bin',
 &
 &OBCS_PARM03
  Urelaxobcsinner=44714.,
  Urelaxobcsbound=2235.7,
  Vrelaxobcsinner=44714.,
  Vrelaxobcsbound=2235.7,
  spongeThickness=20,
 &

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