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<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt">Hi Jean-Michel,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt">Thank you for your previous reply. I conducted a test by changing the `ustressperiod` in `pkg/exf` to zero, but the comparison results did not improve.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt">Here's what I did for the test using `pkg/exf`:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt">1. `ustressperiod = 0`, `umax = 33.0`, `readStressOnCgrid = .TRUE.`<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt">2. `ustressperiod = 0.2` (the interval of my wind stress field), `umax = 33.0`, `readStressOnCgrid = .TRUE.`<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt">3. `ustressperiod = 0.2`, `umax = 15.0`, `readStressOnCgrid = .TRUE.`<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt">In all three cases, a `ustressfile` was specified with dimensions `(nx, 1, nt)`, and `ustress(1:nx, 1, 1:nt) = 0.3`.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt">The results of the three tests (`uVel`, `windstress`, and `uwind`) are exactly the same. According to the output files, `windstress = 0.3 N/m^2`, which is consistent with my intended setup. However,
compared to the results without using `pkg/exf`, where I set up constant wind stress directly in `input/data`, the results using `exf` show a smaller wind-driven current in the surface region (the error is around 0.05 m/s when running for 4 hours).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt">Best,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt">Chichi<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:10.5pt"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><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 Jean-Michel Campin <jmc@mit.edu><br>
<b>Date: </b>Monday, July 15, 2024 at 12:07<br>
<b>To: </b>mitgcm-support@mitgcm.org <mitgcm-support@mitgcm.org><br>
<b>Subject: </b>Re: [MITgcm-support] Setting up external wind stress in ocean model<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Hi Chichi,<br>
<br>
For temporally constant wind stress:<br>
a) without pkg/exf: <br>
wind-stress is supposed to be provided on C-grid ;<br>
and with periodicExternalForcing=F (i.e., the default), it's constant in time.<br>
b) with pkg/exf: <br>
need to specify grid location (either: readStressOnAgrid=T or readStressOnCgrid=T,<br>
in data.exf, EXF_NML_01);<br>
and setting "ustressperiod = 0." will result in constant in time wind-stress forcing.<br>
Note that for this case, if using spacial interpolation, the code for constant wind-stress
<br>
is a bit more complicated than for other exf forcing fields (see comments in exf_init_varia.F,<br>
lines 65-69).<br>
<br>
So, in your case, I would try to change ustressperiod setting to zero and check if the
<br>
comparison improves.<br>
<br>
Cheers,<br>
Jean-Michel<br>
<br>
On Fri, Jul 12, 2024 at 09:24:09PM +0000, Chichi Zhou wrote:<br>
> Hello everyone,<br>
> <br>
> I'm conducting a 2-D simulation in the x-z plane and would like to add spatially and temporally constant wind stress 0.3 N/m^2 at ocean surface. I have tried two methods:<br>
> <br>
> (1) Specify the wind file in `input/data` and do not use the EXF package.<br>
> <br>
> &PARM05<br>
> hydrogThetaFile='T.init',<br>
> bathyFile='flat_bottom',<br>
> uVelInitFile='U.init',<br>
> zonalWindFile='windx.bin',<br>
> <br>
> Here, 'windx.bin' is a 1-D array with dimensions (nx, 1), where windx (1:nx, 1) = 0.3. ?nx? is the total number of grid points in the x direction.<br>
> <br>
> (2) Set up the wind stress in `input/data.exf`.<br>
> <br>
> &EXF_NML_02<br>
> ustressfile = 'windx.bin',<br>
> ustressperiod = 0.2,<br>
> &<br>
> <br>
> Here 'windx.bin' is converted from a matrix with dimensions (nx, 1, nt). windx (1:nx, 1, 1:nt) = 0.3. `nx` is the grid points in the x direction, and ?nt? is the total time steps. ?ustressperiod = 0.2? because `dt = 0.2s`.<br>
> <br>
> However, the output velocity and temperature fields from the two numerical simulations are different. I am confused about the reason of this and would appreciate any suggestions you might have. Thank you in advance!<br>
> <br>
> Best,<br>
> Chichi<br>
> <br>
<br>
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