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Hi Jean-Michel,</div>
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<br>
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Many thanks for this clarification, this makes sense and has cleared up all confusion.</div>
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Thanks again,</div>
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Flynn</div>
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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 Jean-Michel Campin <jmc@mit.edu><br>
<b>Sent:</b> 28 February 2023 2:26 PM<br>
<b>To:</b> mitgcm-support@mitgcm.org <mitgcm-support@mitgcm.org><br>
<b>Subject:</b> Re: [MITgcm-support] rSphere definition when using 'deepAtmosphere' option for ocean modelling - quick question</font>
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<div class="PlainText">Hi Flynn,<br>
<br>
I will try to clarify how the deepAtmosphere (deepAtmosphere=TRUE) scaling is computed:<br>
<br>
It really depends what vertical coordinate you are using:<br>
1) using Z-cordinate: <br>
scaling fct (i.e., distance from center of the sphere) is "rSphere+rF" (level interface)<br>
or "rSphere+rC" (level center), and since rF(1) = seaLev_Z<br>
(with default seaLev_Z value =0)), it means the "rSphere" value correspond to the top<br>
of the model (where the free-surface is).<br>
2) using P-coordinate:<br>
scaling fct (i.e., distance from center of the sphere) is "rSphere+phiRef/gravity"<br>
which means that:<br>
a) for Ocean in P-coord, since at the top phiRef = seaLev_Z*gravity (but this time
<br>
the top is at rF(Nr+1)), the "rSphere" value correspond also to the top of the model<br>
(assuming we are using the default seaLev_Z=0 value).<br>
b) for Atmosphere in P-coord,<br>
since phiRef = seaLev_Z*gravity at the bottom (i.e., at rF(1)), the "rSphere" value
<br>
correspond to the bottom of the model.<br>
<br>
Cheers,<br>
Jean-Michel<br>
<br>
On Mon, Feb 27, 2023 at 04:39:26PM +0000, Flynn Ames wrote:<br>
> Dear MITgcm community,<br>
> <br>
> Hello - I'm hoping to sanity check my interpretation of the 'rsphere' parameter in the MITgcm.<br>
> <br>
> I've been interpreting rsphere as the distance to the top of the model domain (surface of the ocean).<br>
> However, it was recently pointed out to me that rSphere could instead potentially refer to the distance to the bottom of the model domain (bottom of the ocean).<br>
> <br>
> In the code, in the file 'set_grid_factors.F', it appears the computation of the deepAtmosphere adjustments to the grid cell size assume the radius is defined at the top of the domain (the adjustment factor appears to create a smaller cell for increasing
Nr). So it seems my initial interpretation could be correct. Though I was wondering if someone else could confirm this?<br>
> <br>
> My ocean model has the 'deepAtmosphere' option turned on (with an ocean depth comparable to the radius of the sphere), so this interpretation will have significant effects upon my results.<br>
> <br>
> <br>
> Thanks for your time!<br>
> Flynn<br>
> <br>
<br>
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