[MITgcm-support] the OBCS Eta problem

[Chun-Yan Zhou]

Dear all, 
 I just ran a simple case to test the OBCS package with uniform depth=90m, and give tidal boundary velocity at the East and West boundary. I have checked the velocities at the west and east boundary and they are fine. I thought it will calculate the Eta according to the continuous equation given the boundary velocity. But when it comes to Eta, it turned out to be always zero at  the East and West boundary.  
How to deal with this? Adding the prescribed OBEeta and OBWeta file? Maybe it's simple to calculate the bounday Eta with simple topography and simple boundary velocities, however, in most cases with complex topography, what I should to do with the boundary Eta? 
 Thanks for any suggestion. 
chunyan 


  
# ==================== 
# | Model parameters | 
# ==================== 
# 
# Continuous equation parameters 
 &PARM01 
 sRef=60*35., 
 viscA4=0.0E4, 
 viscAh=1.E-3, 
 viscAz=1.E-5, 
 no_slip_sides=.FALSE., 
 no_slip_bottom=.FALSE., 
 diffK4T=0.E4, 
 diffKhT=1.E-3, 
 diffKzT=1.E-5, 
 diffK4S=0.E4, 
 diffKhS=0.E-2, 
 diffKzS=0.E-5, 
 implicitDiffusion=.TRUE., 
 implicitViscosity=.TRUE., 
 f0=0.e-4, 
 beta=0.E-11, 
 eosType='LINEAR', 
 tAlpha=2.E-4, 
 sBeta =0.E-4, 
 gravity=9.81, 
 gBaro=9.81, 
 rigidLid=.FALSE., 
 saltStepping=.FALSE., 
 implicitFreeSurface=.TRUE., 
 hFacMin=0.05, 
 nonHydrostatic=.TRUE., 
 readBinaryPrec=64, 
#- not safe to use globalFiles in multi-processors runs 
#globalFiles=.TRUE., 
 staggerTimestep=.TRUE., 
 & 

# Elliptic solver parameters 
 &PARM02 
 cg2dMaxIters=300, 
 cg2dTargetResidual=1.E-13, 
 cg3dMaxIters=20, 
 cg3dTargetResidual=1.E-8, 
 & 

# Time stepping parameters 
 &PARM03 
 nIter0=0, 
 nTimeSteps=8000, 
#nTimeSteps=8640, 
 deltaT=22.357, 
 abEps=0.01, 
 pChkptFreq=44714., 
 chkptFreq=0.0, 
 dumpFreq=4471.4, 
#taveFreq=864000.0, 
 monitorSelect=2, 
 monitorFreq=1., 
 periodicExternalForcing=.TRUE., 
 externForcingPeriod=223.57, 
 externForcingCycle=44714., 
 & 

# Gridding parameters 
 &PARM04 
 usingCartesianGrid=.TRUE., 
 delX=700*500., 
 dYspacing=50000., 
 delZ=60*1.5, 
 & 

# Input datasets 
 &PARM05 
 bathyFile='topog', 
 hydrogThetaFile='T.init', 
 & 

# Open-boundaries 
 &OBCS_PARM01 
 OB_Ieast=-1, 
 OB_Iwest=1, 
 useOBCSprescribe=.TRUE.,  
 useOBCSsponge=.TRUE., 
 OBEuFile = 'OBEU.bin', 
 OBEvFile = 'OBEV.bin', 
 OBEwFile = 'OBEw.bin', 
 OBEtFile = 'OBEt.bin', 
 OBWuFile = 'OBWU.bin', 
 OBWvFile = 'OBWV.bin', 
 OBWwFile = 'OBWw.bin', 
 OBWtFile = 'OBWt.bin', 
 & 
gendata.m  
ieee='b'; 
prec='real*8'; 
nz=60;ny=1; 
uW=zeros(ny,nz,200); 
uE=zeros(ny,nz,200); 
vW=zeros(ny,nz,200); 
wW=zeros(ny,nz,200); 
for t=1: 200  %weat boundary u velocity 
    uW(:,:,t)=-0.025*20*sin(2*pi*t/200); 
end 
fid=fopen('OBWU.bin','w',ieee); fwrite(fid,uW,prec); fclose(fid); 
fid=fopen('OBWV.bin','w',ieee); fwrite(fid,vW,prec); fclose(fid);%weat boundary v velocity f0=0 
fid=fopen('OBEV.bin','w',ieee); fwrite(fid,vW,prec); fclose(fid);%east boundary v velocity f0=0 

fid=fopen('OBWw.bin','w',ieee); fwrite(fid,wW,prec); fclose(fid);%east and west w velocity=0 
fid=fopen('OBEw.bin','w',ieee); fwrite(fid,wW,prec); fclose(fid); 

for t=1: 200%East boundary u velocity  
    uE(:,:,t)=-0.025*20*sin(2*pi*t/200); 
end 
fid=fopen('OBEU.bin','w',ieee); fwrite(fid,uE,prec); fclose(fid); 
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