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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">I would have guessed that KPP is still required. With an aspect ratio of 1:200 this simulation should still be in the hydrostatic regime, despite the high resolution.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">If you have the computational resources you could try reducing dx and running a non-hydrostatic simulation without KPP.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Cheers,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Ed<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">MITgcm-support <mitgcm-support-bounces@mitgcm.org> on behalf of Dimitris Menemenlis <dmenemenlis@gmail.com><br>
<b>Reply to: </b>"mitgcm-support@mitgcm.org" <mitgcm-support@mitgcm.org><br>
<b>Date: </b>Friday, 3 April 2020 at 05:53<br>
<b>To: </b>MITgcm Support <mitgcm-support@mitgcm.org><br>
<b>Subject: </b>Re: [MITgcm-support] [EXTERNAL] Banding, Checkerboarding in KPP Viscosities<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">So I wonder if you need KPP turned on with such high resolution?<br>
<br>
> On Apr 2, 2020, at 11:06 AM, Senja Walberg <senja.w@gmail.com> wrote:<br>
> <br>
> Greetings,<br>
> <br>
> I have been conducting simulations of a lake and using KPP for vertical mixing. I encountered an issue of noise in derived |grad_h T| fields and traced it to checkerboarding in KPPdiffT and KPPviscA. Based on a 2004 discussion between Dimitris and Martin
I found that the horizontal checkerboarding could be fixed by toggling on the KPP_SMOOTH_DENS flag in KPP_OPTIONS.h. However, I am still encountering vertical banding. Attached is a snapshot of this banding from a simplified lake simulation.<br>
> <KPPviscA_y_Support.jpg><br>
> The lake is stratified between ~25 degrees at the top and ~10 degrees at the bottom with the pycnocline at 15 m. I am using dz=0.5 m and dx=100m.<br>
> <br>
> I have tried turning on KPP_SMOOTH_VISC, KPP_SMOOTH_DIFF, and ALLOW_KPP_VERTICALLY_SMOOTH, as well as increasing both horizontal and vertical viscosities and diffusivities, and have had no luck getting rid of this banding.<br>
> <br>
> I'm currently experimenting with changing the vertical resolution to see what effect that has, but would like to not be constrained to a coarse vertical grid if there is some fix to this.<br>
> <br>
> Does anybody know what's causing this issue or how it can be resolved? <br>
> <br>
> Regards,<br>
> Senja<br>
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