<div dir="ltr"><div><div>The documentation and argument prototyping indicates that latitude and longitudes are expected. The function works on a sphere and uses distances calculated via great circle distance formula. <br><br>function rcm2rgrid (
<pre> lat2d [*][*] : numeric,
lon2d [*][*] : numeric,
fi : numeric,
lat [*] : numeric,
lon [*] : numeric,
Option : numeric
)</pre>Hence, this is not the appropriate function to use.<br>========<br><br><a href="https://www.ncl.ucar.edu/Document/Functions/interp.shtml">https://www.ncl.ucar.edu/Document/Functions/interp.shtml</a><br><br></div>There are numerous interpolation functions. Maybe<br><br>==<br><a href="https://www.ncl.ucar.edu/Document/Functions/Built-in/dsgrid2.shtml">https://www.ncl.ucar.edu/Document/Functions/Built-in/dsgrid2.shtml</a><br><a href="https://www.ncl.ucar.edu/Document/Functions/Built-in/natgrid.shtml">https://www.ncl.ucar.edu/Document/Functions/Built-in/natgrid.shtml</a><br>==<br><br></div>Still, I'm not sure if these are appropriate for doubly periodic boundary conditions.<br><div><div><div><br><br></div></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Mar 22, 2016 at 11:58 AM, Michael Toy <span dir="ltr"><<a href="mailto:toy@ucar.edu" target="_blank">toy@ucar.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><div>Hello,</div><div><br></div><div>I am using the function “rcm2rgrid” to interpolate a 2D field onto a Cartesian grid from a smooth non-orthogonal curvilinear grid. Note that I am not on the sphere, but on an idealized flat plane with doubly periodic boundary conditions. When the field, which is relative vorticity (zeta), is plotted in the native curvilinear coordinate, the contours are smooth. However, when the interpolated field is plotted, the contours appear very ragged. I don’t know where the “noise” is coming from. I’m wondering if “rcm2rgrid” is the appropriate interpolation function for what I’m trying to do.</div><div><br></div><div>I’ve attached the *.ncl file I’m using which reads in a netcdf file with the data in the native curvilinear coordinate (a 3.8MB file stored on Google Drive at the following link):</div><div><div style="margin:0px"><a href="https://drive.google.com/file/d/0B5l8e_K0c8ymRnBqUm0xOGhSS0U/view?usp=sharing" target="_blank">https://drive.google.com/file/d/0B5l8e_K0c8ymRnBqUm0xOGhSS0U/view?usp=sharing</a></div></div><div style="margin:0px"><br></div><div style="margin:0px">The interpolated data is stored to a file named “<a href="http://zeta_xy.troubleshoot.nc" target="_blank">zeta_xy.troubleshoot.nc</a>”. The first plot generated is zeta in the native coordinate, followed by the interpolated zeta, followed by a panel plot showing both fields.</div><div style="margin:0px"><br></div><div style="margin:0px">The version of NCL I’m using is 6.3.0. Any help with producing smoother interpolated fields would be appreciated. Thanks!</div><div style="margin:0px"><br></div><div style="margin:0px">— Mike</div><div style="margin:0px"><br></div><div style="margin:0px"><br></div><div style="margin:0px"><br></div><div style="margin:0px"></div></div><br><div style="word-wrap:break-word"><div style="margin:0px"></div></div><br>_______________________________________________<br>
ncl-talk mailing list<br>
<a href="mailto:ncl-talk@ucar.edu">ncl-talk@ucar.edu</a><br>
List instructions, subscriber options, unsubscribe:<br>
<a href="http://mailman.ucar.edu/mailman/listinfo/ncl-talk" rel="noreferrer" target="_blank">http://mailman.ucar.edu/mailman/listinfo/ncl-talk</a><br>
<br></blockquote></div><br></div>