<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="">Hi Yang<div class=""><br class=""></div><div class="">I have never seen SSH be unbalanced with </div><div class=""><div class="">OBCSbalance = true</div><div>How slow is the drift? Could it be associated with something else (e.g. freshwater or heat forcing)?</div><div><br class=""></div><div>Regarding " <b class="" style="font-family: "Microsoft YaHei"; font-size: inherit;"></b><span class="" style="white-space: pre-wrap;">have the bathy gradient normal to the wall = 0 in the sponge; turn off </span><span class="" style="white-space: pre-wrap;">tangential velocity; </span><span class="" style="white-space: pre-wrap;">making the corners in the sponge layer have depth 0”</span></div><div><span class="" style="white-space: pre-wrap;">These are not really for balance. These are to prevent a spurious wave guide, spurious mixing, and forced divergence at the boundary.</span></div><div><span class="" style="white-space: pre-wrap;"><br class=""></span></div><div><span class="" style="white-space: pre-wrap;">Matt</span></div><div><span class="" style="white-space: pre-wrap;"><br class=""></span></div><div><span class="" style="white-space: pre-wrap;"><br class=""></span></div><div><br class=""><blockquote type="cite" class=""><div class="">On Apr 12, 2019, at 8:49 AM, yang zhibin <<a href="mailto:853245241@qq.com" class="">853245241@qq.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">Hi all,</div><div class=""><br class=""></div><div class="">Recently I am running a regional model with OBCS. For the purpose of volum balance, I use OBCSbalance. However, there still exist SSH drift (though slow). </div><div class="">I checked the previous maillist and found a similar question about five years ago (<a href="http://mailman.mitgcm.org/pipermail/mitgcm-support/2014-July/009288.html" class="">http://mailman.mitgcm.org/pipermail/mitgcm-support/2014-July/009288.html</a>). Thanks to the reply of previous modeler on this question.</div><div class="">In that mail, Mattew gave a complex process to solve this problem (e.g. <b style="font-family: "Microsoft YaHei"; font-size: inherit;" class=""></b><span style="white-space: pre-wrap;" class="">have the bathy gradient normal to the wall = 0 in the sponge; turn off </span><span style="white-space: pre-wrap;" class="">tangential velocity; </span><span style="white-space: pre-wrap;" class="">making the corners in the sponge layer have depth 0). I wonder if the zero </span><span style="white-space: pre-wrap;" class="">tangential velocity could affect inner or the sponge layer? In the end, </span>Mattew also suggest use RBCS instead of OBCS. But could the volum balance without OBCSbalance?</div><div class=""><br class=""></div><div class="">Cheers,</div><div class="">Yang</div>_______________________________________________<br class="">MITgcm-support mailing list<br class=""><a href="mailto:MITgcm-support@mitgcm.org" class="">MITgcm-support@mitgcm.org</a><br class="">http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support<br class=""></div></blockquote></div><br class=""></div></body></html>