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<p>Hi James,</p>
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<p>When the GFS went to 0.25 degree output last year, the fishpak routines became unreliable for the GFS:</p>
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<p><a title="Ctrl+Click or tap to follow the link" id="LPlnk49616" href="http://opengrads.org/doc/udxt/fish/fish.html">http://opengrads.org/doc/udxt/fish/fish.html</a></p>
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<p>"Notice that <code>fish()</code> becomes numerically unstable for horizontal resolutions finer that 1/2 degrees or so. In such cases use the spherical harmonic based
<strong>sh_fish</strong> given in extension <em>shfilt</em>."</p>
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<p>Indeed, I have found sh_fish is a very reliable replacement at these resolutions.</p>
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<p>Bob Hart<br>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt" face="Calibri, sans-serif" color="#000000"><b>From:</b> gradsusr-bounces@gradsusr.org <gradsusr-bounces@gradsusr.org> on behalf of James Spinks <jspin881@hotmail.com><br>
<b>Sent:</b> Wednesday, March 23, 2016 4:22 PM<br>
<b>To:</b> gradsusr@gradsusr.org<br>
<b>Subject:</b> [gradsusr] Streamfunction (fish_psi)</font>
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<div dir="ltr">Hello,<br>
<br>
I'm having some trouble using the fish_psi function to plot streamfunction for the GFS data.<br>
<br>
'open gfs.ctl'<br>
'd fish_psi(ugrdprs,vgrdprs)'<br>
<br>
The field is returning constant value 0 or -inf.<br>
<br>
Interestingly enough, I use to be able to plot streamfunction using fish_psi with no problem for the GFS. So this 'bug' has occurred over the last few months or so.<br>
<br>
Anyone have any ideas what may be causing the problem with the GFS data? I have use the function fish_psi just fine using the ECMWF-interim data.
<br>
<br>
I'm using grads-2.1.a2.oga.1<br>
<br>
Thanks,<br>
James Spinks<br>
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