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<p>Hi Jody, thanks for the reply.</p>
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<p>If you look on line 390 in kpp_calc.F (<a href="http://lxr.mitgcm.org/lxr2/source/MITgcm/pkg/kpp/kpp_calc.F" class="OWAAutoLink" id="LPlnk260358" previewremoved="true">http://lxr.mitgcm.org/lxr2/source/MITgcm/pkg/kpp/kpp_calc.F</a>), there is a comment that
says</p>
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<p>bo = -g *( alpha * surfaceForcingT + beta * surfaceforcingS) / rho</p>
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<p>which is what lead me to assume that the equation of state was hardcoded to be linear. </p>
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<p>However, that assumption is wrong because I see a little while later that the expansion coefficient, alpha, is calculated via a function that talks with the equation of state. This means that alpha could be positive or negative which takes care of the case
when you have an inverse stratification. </p>
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<p>I guess I just didn't look far enough. </p>
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<p>Thanks</p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> MITgcm-support <mitgcm-support-bounces@mitgcm.org> on behalf of Jody Klymak <jklymak@uvic.ca><br>
<b>Sent:</b> January 3, 2020 3:31:57 PM<br>
<b>To:</b> mitgcm-support@mitgcm.org<br>
<b>Subject:</b> Re: [MITgcm-support] KPP with inverse stratification</font>
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<div>Hi Andrew,
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<div class="">I didn’t spend a lot of time looking, but KPP seems to call `FIND_RHO_2D` to calcualate (for instance) `dbloc`, which should return whatever density you specified in your equation of state. </div>
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<div class="">Where did you see that it is hardcoded? </div>
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<div class="">Cheers, Jody<br class="">
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<div class="">On 3 Jan 2020, at 11:32, Andrew Grace <<a href="mailto:andrew.grace@uwaterloo.ca" class="">andrew.grace@uwaterloo.ca</a>> wrote:</div>
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Hi all, </div>
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I'm trying to use the KPP package in a freshwater setup but the water temperatures are all below the density maximum, meaning that cooler water over warm water is stable. I noticed that in kpp_calc.F, the surface buoyancy is calculated using a hardcoded linear
equation of state, and therefore, when then code determines the stability of the water column, it is deemed unstable when it should not be. This is how I understand it. </div>
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I just want to confirm that the KPP package requires modification before it can be used in situations where an inverse stratification is stable. I also apologize if this question has been asked before. </div>
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Thanks in advance.</div>
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<div class="">--</div>
<div class="">Jody Klymak </div>
<div class=""><a href="http://web.uvic.ca/~jklymak/" class="">http://web.uvic.ca/~jklymak/</a></div>
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