<html><head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<p>Hi MohammadHossein,</p>
<p><br>
</p>
<p>You might have unbalanced fluxes on the open boundaries.
Specifically, you haven't set useOBCSbalance=.TRUE. in data.obcs.</p>
<p><br>
</p>
<p>Recently, I had a regional model whose sea surface height changed
by 100m over one month! The lack of balancing was the cause.</p>
<p><br>
</p>
<p>Ken Hughes<br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 2022-08-23 11:43 a.m.,
Mohammadhossein Kharaghani wrote:<br>
</div>
<blockquote type="cite" cite="mid:1661280210920.57481@civileng.iust.ac.ir">
<style type="text/css" style="display:none"><!-- p { margin-top: 0px; margin-bottom: 0px; }--></style>
<p><span style="color:#D73F09;">[This email originated from
outside of OSU. Use caution with links and attachments.]</span></p>
<div>
<p>Hello MITgcm community<br>
</p>
<p>I have a simple model with three open boundaries in the
north, east and west, and in this model that Tide is given to
the model as a time series (including 8 components) up to 30
hours (more than one period).There is no problem in the
topography and input data of open boundaries. However, sea
surface elevation(eta) in my model rises quickly and greatly
at all points from the start of running, thus, the model
quickly becomes unstable. Griding and dimensions of the model
are as follows:</p>
<p>The grid in the horizontal direction is equal to ten meters
and in the vertical direction it has 14 layers of 0.5, 1 and 2
meters from the surface to the floor. The range of the model
is as 1.18 km x 0.8 km and the maximum depth is 15 meters.<br>
</p>
<p>Best regards<br>
</p>
<p>MohammadHossein<br>
</p>
<p><br>
</p>
<p><strong>Data file:</strong></p>
<p> &PARM01</p>
<p> Tref = 21.084700, 21.020412, 20.977085, 20.948000,
20.928308, 20.914621, 20.896999, 20.885466, 20.877001,
20.870974, 20.864302, 20.859730, 20.857693, 20.853001,
</p>
<p> sRef= 41.913029, 41.911030, 41.909740, 41.908958, 41.908516,
41.908287, 41.908123, 41.908012, 41.907799, 41.907497
41.907089, 41.906998, 41.906975, 41.906933,
</p>
<p> viscAz=1.E-3,</p>
<p> viscAh=1.E-2,</p>
<p> no_slip_sides=.FALSE.,</p>
<p> no_slip_bottom=.FALSE.,</p>
<p> diffKhT=1.E-2,</p>
<p> diffKzT=1.E-3,</p>
<p> diffKhS=1.E-2,</p>
<p> diffKzS=1.E-3,</p>
<p># saltAdvScheme=4,</p>
<p> f0=0.0,</p>
<p> beta=0.E-11,</p>
<p> eosType='LINEAR',</p>
<p> tAlpha=2.E-4,</p>
<p> sBeta =0.E-4,</p>
<p> gravity=9.81,</p>
<p> implicitFreeSurface=.TRUE.,</p>
<p> rigidLid=.FALSE.</p>
<p> implicitDiffusion=.FALSE.,</p>
<p> exactConserv=.TRUE.,</p>
<p> nonHydrostatic=.FALSE.,</p>
<p> hFacMin=1.0,</p>
<p> implicSurfPress=1.0,</p>
<p> implicDiv2DFlow=1.0,</p>
<p> nonlinFreeSurf=1,</p>
<p> hFacInf=0.2,</p>
<p> hFacSup=1.8,</p>
<p> saltStepping = .FALSE.,</p>
<p> tempStepping = .FALSE.,</p>
<p>#- not safe to use globalFiles in multi-processors runs</p>
<p>#globalFiles=.TRUE.,</p>
<p> readBinaryPrec=64,</p>
<p> writeBinaryPrec=64,</p>
<p> writeStatePrec=64,</p>
<p> &</p>
<p># Elliptic solver parameters</p>
<p> &PARM02</p>
<p> cg2dMaxIters=500,</p>
<p> cg2dTargetResidual=1.E-13,</p>
<p> cg3dMaxIters=400,</p>
<p> cg3dTargetResidual=1.E-13,</p>
<p> &</p>
<p># Time stepping parameters</p>
<p> &PARM03</p>
<p> nIter0=0,</p>
<p> nTimeSteps=108000,</p>
<p> deltaT=1.0,</p>
<p> pChkptFreq=3600.,</p>
<p> chkptFreq=0.,</p>
<p> dumpFreq=3600,</p>
<p> monitorFreq=1.,</p>
<p> monitorSelect=2,</p>
<p># for time dependent open boundary conditions, activate the
following 3 lines:</p>
<p> periodicExternalForcing=.TRUE.,</p>
<p> externForcingPeriod=3600.,</p>
<p> externForcingCycle =108000.,</p>
<p> &</p>
<p># Gridding parameters</p>
<p> &PARM04</p>
<p> usingCartesianGrid=.TRUE.,</p>
<p> dySpacing=10.,</p>
<p> dxSpacing=10.,</p>
<p> delZ=0.5,0.5,0.5,0.5,0.5,0.5,1.0,1.0,1.0,1.0,2.0,2.0,2.0,2.0,</p>
<p> &</p>
<p># Input datasets</p>
<p> &PARM05</p>
<p> bathyFile='TopoKharg4',</p>
<p> &<br>
</p>
<p><br>
</p>
<p><strong>Data.obcs file</strong></p>
<p># Open boundaries</p>
<p> &OBCS_PARM01</p>
<p> OB_Jnorth = 118*-1,</p>
<p> OB_Iwest = 80*1,</p>
<p> OB_Ieast = 80*-1,</p>
<p> useOBCSsponge = .TRUE.,</p>
<p># This flag check and equalise topography across open
boundaries:</p>
<p> OBCSfixTopo = .FALSE.,</p>
<p> useOBCSprescribe= .TRUE.,</p>
<p> OBNuFile='OBNut.iwkharg_obcs',</p>
<p> OBNvFile='OBNvt.iwkharg_obcs',</p>
<p> OBWuFile='OBWut.iwkharg_obcs',</p>
<p> OBWvFile='OBWvt.iwkharg_obcs',</p>
<p> OBEuFile='OBEut.iwkharg_obcs',</p>
<p> OBEvFile='OBEvt.iwkharg_obcs',</p>
<p> OBEetaFile='OBEeta.iwkharg_obcs',</p>
<p> OBNetaFile='OBNeta.iwkharg_obcs',</p>
<p> OBWetaFile='OBWeta.iwkharg_obcs',</p>
<p> OBCS_monitorFreq= 1.,</p>
<p> OBCS_monSelect = 1,</p>
<p> &</p>
<p> &OBCS_PARM03</p>
<p> spongeThickness= 10 ,</p>
<p> Urelaxobcsinner= 1000,</p>
<p> Vrelaxobcsinner= 1000,</p>
<p> Urelaxobcsbound= 100,</p>
<p> Vrelaxobcsbound= 100,</p>
<p> &<br>
</p>
<p><br>
</p>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<pre class="moz-quote-pre" wrap="">_______________________________________________
MITgcm-support mailing list
<a class="moz-txt-link-abbreviated" href="mailto:MITgcm-support@mitgcm.org">MITgcm-support@mitgcm.org</a>
<a class="moz-txt-link-freetext" href="http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support">http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support</a>
</pre>
</blockquote>
</body>
</html>