<div dir="ltr">Hello everyone!<div><br></div><div>Having tested my several MITgcm configurations (details here: <a href="http://mailman.mitgcm.org/pipermail/mitgcm-support/2020-April/012462.html">http://mailman.mitgcm.org/pipermail/mitgcm-support/2020-April/012462.html</a>) I encountered an issue with the model results. For unknown reasons the sea level has high oscillations and drops (up to minus 3-6 m) which can not be explained by the prescribed external forcing and OBCS (they are OK, SSH = plus/minus 1 m at the boundary). Also, delR=2 m in the upper layers, and minimum depth in the domain is 5 m. No tides, no sponge.</div><div><br></div><div>At each time step the model used <span style="background-color:rgb(252,252,252);font-family:"Times New Roman",serif;font-size:12pt">SURF_ADJUSTMENT...</span></div><div><br></div><div>Below are some parameters from the data file used for the reference run (№ 0):</div><div> &PARM01</div><div> hFacMin = 0.2,</div><div> hFacMinDr = 0.5,</div><div> hFacInf = 0.2,</div><div> hFacSup = 2.0,</div><div> vectorInvariantMomentum = .TRUE.,</div><div> highOrderVorticity = .TRUE.,</div><div> rigidLid = .FALSE.,</div><div> implicitFreeSurface = .TRUE.,</div><div> nonlinFreeSurf = 4,</div><div> select_rStar = 0,</div><div> exactConserv = .TRUE.,</div><div> useRealFreshWaterFlux = .TRUE.,</div><div> staggerTimeStep = .TRUE.,</div><div> multiDimAdvection = .TRUE.,</div><div> implicitViscosity = .TRUE.,</div><div> implicitDiffusion = .TRUE.,</div><div> viscAhGrid = 0.0,</div><div> viscAhGridMax = 0.5,</div><div> viscC2leith = 1.0,</div><div> viscC2leithD = 1.0,</div><div> useFullLeith = .TRUE.,</div><div> viscAr = 1.0e-4,</div><div> no_slip_sides = .FALSE.,</div><div> no_slip_bottom = .TRUE.,</div><div> bottomDragQuadratic = 0.0025,</div><div> tempAdvScheme = 33,</div><div> saltAdvScheme = 33,</div><div> diffKhT = 0.0,</div><div> diffKhS= 0.0,</div><div> diffKrT = 1.0e-4,</div><div> diffKrS = 1.0e-4,</div><div> useSingleCpuIO = .TRUE.,</div><div> &</div><div> forcing_In_AB = .FALSE.,</div><div> momDissip_In_AB = .FALSE.,</div><div> cAdjFreq = -1.0,</div><div> usingCurvilinearGrid = .TRUE.,</div><div><br></div><div>Having s<font face="arial, sans-serif">potted such erroneous results in STDOUT statistics, I started tuning some model's functionality to figure out what happened. Some conclusions for the subsequent runs:</font></div><div><font face="arial, sans-serif">1) I turn off the river runoff everywhere in OBCS. The problem remained.</font></div><div><font face="arial, sans-serif">2) + I removed eta boundary conditions from data.obcs.
The problem remained.
</font></div><div><font face="arial, sans-serif">3) + I set <span style="line-height:115%;background:rgb(252,252,252)">useOBCS =
.FALSE. in </span><span lang="EN-US" style="line-height:115%;background:rgb(252,252,252)">data</span><span style="line-height:115%;background:rgb(252,252,252)">.</span><span lang="EN-US" style="line-height:115%;background:rgb(252,252,252)">pkg, thus closed all the open boundaries, suspecting them. But the problem remained.</span></font></div><div><font face="arial, sans-serif"><span lang="EN-US" style="line-height:115%;background:rgb(252,252,252)">4) I returned to the initial settings (run № 0, see above), but set: </span>nonlinFreeSurf = 0 and linFSConserveTr = .TRUE., and the problem vanished, no SURF_ADJUSTMENT in the STDOUT any more!</font></div><div><font face="arial, sans-serif">5) <span lang="EN-US" style="line-height:115%;background:rgb(252,252,252)">I returned to the initial settings (run № 0, see above), but set: </span>nonlinFreeSurf = 4 and
select_rStar = 2,
, and get the followng message from one of tiles:</font></div><div> fail at i,j= 44 39 ; rStarFacC,H,eta = 0.199701 5.000000E+00 -4.001496E+00<br>WARNING: r*FacC < hFacInf at 1 pts : bi,bj,Thid,Iter= 1 1 1 350<br>STOP in CALC_R_STAR : too SMALL rStarFac[C,W,S] !<font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif"><br></font></div><div><font face="arial, sans-serif">Could you please help me to figure out:</font></div><div><font face="arial, sans-serif">a) If I want to use non-linear free suface but do not want to use rStar, may I set select_rStar=0 and nonlinFreeSurf=4
simultaniously? In the verification '<span style="background-color:rgb(252,252,252)">internal_wave' I found </span><span style="background-color:rgb(252,252,252)">nonlinFreeSurf=3 and </span><span style="background-color:rgb(252,252,252)">select_rStar=0. So, for </span>select_rStar=0 the parameter nonlinFreeSurf=0 is not a must?</font></div><div><font face="arial, sans-serif">b) When selecting </font>nonlinFreeSurf=4 and
select_rStar=2 the model crushes complaining about too SMALL rStarFac[C,W,S]. My vertical resolution is too small (2 m) or I should change the hFacMin or hFacDr somehow?</div><div><font face="arial, sans-serif">c) Where does the key DISABLE_RSTAR_CODE come from? It is used in many checks throughout the code, but I could not find where it is defined. Should I change it if I do not want to use rStar? Or using just select_rStar=0 is enough?</font></div><div><font face="arial, sans-serif">d) Does the parameter hFacInf works only in the case of nonlinFreeSurf != 0, keeping the upper layer alive? What if I use
nonlinFreeSurf= 0 and at some moment -eta > dr(1)? The upper layer thickness may become 0 when </font>nonlinFreeSurf=0?</div><div><br></div><div>Thanks!</div><div><br></div><div>Regards,</div><div>Stanislav Martyanov</div></div>