<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Dear MITgcm-ers,<br class=""><div><div style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class=""><br class=""></div><div class="">We are running high-resolution regional simulations in marginal seas of the Mediterranean (and sub-basins).</div><div class="">At resolutions ranging from 1/128° to 1/768° (some examples, respectively, <a href="https://medeaf.ogs.it/adriatic" class=""><b class="">here</b></a> and <a href="https://medeaf.ogs.it/got" class=""><b class="">here</b></a>), we insert the river inputs as lateral open boundary conditions, since the momentum contribution is significant at those scales (and we can also easily control the thermohaline and biogeochemical inputs by prescribing OB files).</div><div class="">The problem arises when we deal with domains fully surrounded by (water) open boundaries (e.g., regional focus on Sicily or Sardinia).</div><div class="">The attached picture shows an idealized case study (island in the open sea), where we want to impose a river originating from the northernmost end of the channel and flowing southward. If we impose a single land point at the northern edge of the model domain (i_g=21 and j_g=41, plot on the right), we can set an OB point at i_g=21 and j_g=21 and the simulation runs smoothly. Conversely, the configuration on the left cannot work (as far as we know...).</div><div class="">We also tried to use the "<b style="font-style: normal;" class=""><font face="Menlo" class="">insideOBmaskFile</font></b>" as specified in the documentation for the <a href="https://mitgcm.readthedocs.io/en/latest/phys_pkgs/obcs.html#a-more-complex-example" class=""><b class="">more complex example</b></a>, but we are a bit stuck...</div><div class=""><b class=""><br class=""></b></div><div class=""><b class="">Can you confirm that there is no way to prescribe "inner" OBCs </b>(the river input in i_g=21 and j_g=21) in a domain like the one in the picture (<u class="">left</u>), while keeping the nesting model values <b class="">all around the (nested) domain</b> (also in i_g=21 and j_g=41)?</div><div class="">In that case, we will insert the same <b class="">runoff </b>as <u class="">surface flux</u> by using the <b class="">exf</b> package. Most likely, we will add the freshwater flux in i_g=21 and j_g=21, to let the water gain some momentum along the channel, otherwise, we will remove the channel and simply put the runoff in i_g=21 and j_g=12.</div><div class=""><br class=""></div><div class="">Thank you!</div><div class=""><br class=""></div><div class="">Cheers,</div><div class=""><br class=""></div><div class="">Stefano and Fabio</div><div class=""><br class=""></div><div class="">P.S.: is it possible that there is an oversight in the documentation (Figure 8.6)? The correct OB configuration in <i class="">data.obcs</i> should be like that, do you agree?</div><div class=""><br class=""></div><div class=""><div class=""><font face="Menlo" class="">OB_Iwest = 1*0,1*5,<b class="">1*2</b>,141*0,</font></div><div class=""><font face="Menlo" class="">OB_Jsouth = 2*3,3*2,115*0,</font></div></div><div class=""><br class=""></div><div class="">and not</div><div class=""><br class=""></div><div class=""><div class=""><font face="Menlo" class="">OB_Iwest = 1*0,1*5,142*0,</font></div><div class=""><font face="Menlo" class="">OB_Jsouth = 2*3,3*2,115*0,</font></div></div><div class=""><br class=""></div><div class="">(or the OB routines automatically set i=2, j=3 as the OB position -red line- ?)</div><div class=""><br class=""></div><div class="">--<br class="">Stefano Querin, PhD<br class="">Sezione di Oceanografia<br class="">Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS<br class="">via Beirut n. 2<br class="">34151 Trieste - Italia<br class="">Tel. +39 040 2140623<br class="">Skype: stefano_querin<br class=""><a href="http://www.ogs.it/" class="">www.ogs.it</a><br class=""></div><div class=""><br class=""></div><div class=""><img apple-inline="yes" id="BCA4EACF-9D7F-4FB5-A8DE-FC46D671C8BF" class="" src="cid:3503D346-3980-44AB-9023-80B3DD15C2A4"></div></div></div></body></html>