<div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div>Hello Martin,</div><div><br></div><div> I am using the curvilinear coordinate on the rotating_tank for latitudes 75N-90N by applying the old grids on MITgcm_contrib/arctic40km/ and MITgcm_contrib/arctic/cs_4km. Generally, the numerical disturbances occurred around the lateral boundary and moved back to the center of the domain. Thus, the default lateral boundary condition does not seem to be good enough to handle these disturbances. My experiences with Orlanski radiation condition were really good. Therefore, I updated b.c. by adding obcs in code/packages.conf and having a run/data.obcs as I showed earlier. Although no error messages about boundary condition are in the logfiles of execution, the output patterns are almost exactly the same as the original one. If my updating processes for b.c. was wrong, what else should I do to make it working? </div><div><br></div><div> By the way, I will change the radius of the planet. Those old gids on MITgcm_contrib/arctic40km/ and MITgcm_contrib/arctic/cs_4km will not be suitable for my work on curvilinear coordinates accordingly. Can I change the radius of the planet and focus on latitudes 75N-90N by working on the grids of CS or LLC? I know very little about them.</div><div><br></div><div> Thanks,</div><div><br></div><div> Yi-Chih</div><br><div>Date: Fri, 14 Dec 2018 13:50:11 +0100<br>From: Martin Losch <<a href="mailto:Martin.Losch@awi.de" target="_blank">Martin.Losch@awi.de</a>><br>To: MITgcm Support <<a href="mailto:mitgcm-support@mitgcm.org" target="_blank">mitgcm-support@mitgcm.org</a>><br>Subject: Re: [MITgcm-support] is Orlanski radiation condition working<br> in the rotating rank of MITgcm?<br>Message-ID: <<a href="mailto:CABCD918-87C9-43E4-9B04-053E15DE67EF@awi.de" target="_blank">CABCD918-87C9-43E4-9B04-053E15DE67EF@awi.de</a>><br>Content-Type: text/plain; charset="utf-8"<br><br>Hi Yi-Chih,<br><br>I can only guess what you are trying to do: You use the verification/rotating_tank setup, you probably change f0 from 0.5 to something more ?polar?, e.g. 1.45e-4 for a latitude of 85.5 degN, but then your grid spacing needs to be adjusted (from the lab-scales in the original rotating_tank experiment), etc ? There are many places, where you may not satify stability criteria. See here <<a href="https://mitgcm.readthedocs.io/en/latest/examples/examples.html" rel="noreferrer" target="_blank">https://mitgcm.readthedocs.io/en/latest/examples/examples.html</a>> for examples of stability criteria in other tutorial experiments.<br><br>Introducing open boundary conditions to get rid of grid scale noise is not a good idea. Normally open boundar condition tend to be more of a problem than a solution.<br><br>Martin <br></div></div></div><br><div class="gmail_quote"><div dir="ltr">On Fri, Dec 14, 2018 at 8:27 AM Yi-Chih Huang <<a href="mailto:dscpln@gmail.com">dscpln@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Dear MITgcm experts,<div><br></div><div> I ran into numerical disturbances around the boundary working on the rotating rank of MITgcm in the Arctic regions. I tried to apply Orlanski radiation condition to the rotating rank in data.obcs below. However, the patterns with the data<span class="gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-gr_ gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-gr_347 gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-gr-alert gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-gr_gramm gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-gr_inline_cards gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-gr_run_anim gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-Style gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-replaceWithoutSep" id="gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-347" style="display:inline;border-bottom:2px solid transparent;background-repeat:no-repeat">.<span class="gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-gr_ gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-gr_345 gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-gr-alert gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-gr_spell gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-gr_inline_cards gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-gr_disable_anim_appear gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-ContextualSpelling gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-ins-del gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-multiReplace" id="gmail-m_-7073575648350850882gmail-m_-5744883075929232093gmail-345" style="display:inline;border-bottom:2px solid transparent;background-repeat:no-repeat;color:inherit;font-size:inherit">obcs</span></span> are almost the same as the original one. There is no error message in the log files. Do you think Orlanski radiation condition is working in the rotating rank of MITgcm? How should I update the boundary conditions on MITgcm?</div><div><br></div><div><div># Open-boundaries</div><div> &OBCS_PARM01</div><div> OB_Ieast=102*-1,</div><div> OB_Iwest=102*1,</div><div> OB_Jnorth=130*-1,</div><div> OB_Jsouth=130*1,</div><div> useOrlanskiEast=.TRUE.,</div><div> useOrlanskiWest=.TRUE.,</div><div> useOrlanskiNorth=.TRUE.,</div><div> useOrlanskiSouth=.TRUE.,</div><div># useOBCSbalance=.TRUE.,</div><div># OBCS_balanceFacW= 1.,</div><div># OBCS_balanceFacN= 0.,</div><div> OBCS_monitorFreq=3000.,</div><div> &</div><div><br></div><div> &OBCS_PARM02</div><div> CMAX=0.5,</div><div> cvelTimeScale=10000.,<br></div><div> useFixedCEast=.FALSE.,<br></div><div> useFixedCWest=.FALSE.,</div><div> &</div></div><div><br></div><div> Thanks much,</div><div><br></div><div> Yi-Chih</div></div>
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