[MITgcm-support] How to simulate the geostrophic current?

[miaocb]

Hi MITgcm users,
     With prescribed temperature and salinity which varies horizontally, I need to diagnoise the corresponding geostrophic current.
The geostrophic current could be computed via geostrophic balance: fv = 1/rho*dp/dx, fu = -1/rho*dp/dy. But the problem is how to
implement it using MITgcm. 
     The initial temperature and salinity are spedified in "data", and time step is set to 360 seconds.  During model run rbcs package is 
used to relax temperature and salinity to their initial value. 
 hydrogThetaFile='theta_init.dat'
 hydrogSaltFile='salt_init.dat'
     A 2D configuration with flat topography is used. I found that the geostrophic flow computed depends highly on the  relaxing timescale
(tauRelaxT and tauRelaxS in "data.rbcs") and  viscosity cofficient viscAh in "data". Different advection schemes for temperature and salinity
also give absolutely different results. I don't know how to set proper values for these parameters for such a situation.
    Or are there any other things that should be considered ? I appreciate if someone could help me.

In my best simulation,  tauRelaxT and tauRelaxS  are both taken to be the interial period 2*pi/f0, and other parameters are listed as follows.

# Continuous equation parameters
 &PARM01
 tRefFile='tRef.dat',
 sRefFile='sRef.dat',
 viscA4=0.E12,
 viscAz=1.E-1,
 viscAh=400 !1.E0,
 no_slip_sides=.FALSE.,
 no_slip_bottom=.FALSE.,
 diffKhT=0.E0,
 diffKzT=0.E0,
 diffKhS=0.E0,
 diffKzS=0.E0,
# tempAdvScheme=33,
# saltAdvScheme=33,
 f0=8.000000E-05,
 beta=0.E-11,
 tAlpha=2.E-4,
 sBeta=7.4E-4,
 gravity=9.81,
 gBaro=9.81,
 rigidLid=.FALSE.,
 implicitFreeSurface=.TRUE.,
 eosType=LINEAR,
 hFacMin=0.2,
 nonHydrostatic=.FALSE.,
 readBinaryPrec=64,
 writeBinaryPrec=64,
 globalFiles=.TRUE.,
 saltStepping=.TRUE.,
 implicSurfPress=1.0, 
 implicDiv2DFlow=1.0, 
 nonlinFreeSurf=0,
 hFacInf=0.2,
 hFacSup=1.8,
 exactConserv=.TRUE.,
 useEnergyConservingCoriolis=.TRUE.,
 staggerTimeStep=.TRUE.,
 &

# Elliptic solver parameters
 &PARM02
 cg2dMaxIters=1000,
 cg2dTargetResidual=1.E-13,
 cg3dMaxIters=400,
 cg3dTargetResidual=1.E-13,
 &

# Time stepping parameters
 &PARM03
 startTime=0.0,
 endTime=8640000,
 deltaT=360.000000,
 abEps=0.02,
 pChkptFreq=0.,
 chkptFreq=0., 
 dumpFreq=3600.,
 &

# Gridding parameters
 &PARM04
 usingCartesianGrid=.TRUE.,
 usingSphericalPolarGrid=.FALSE.,
 delXfile='delX.dat',
 delY=1*5000.,
 delRfile='delZ.dat',
 &

# Input datasets
 &PARM05
 bathyFile='topo.dat',
 hydrogThetaFile='theta_init.dat'
 hydrogSaltFile='salt_init.dat'
 &


Thanks,

Paul Miao