<div dir="ltr"><div>I am not sure but<b> </b>he default algorithm used by NCL to plot random data [lon, lat, value] uses some form of triangulation. I believe those spurious 'lines' are an artifact of that.<br></div><div><br></div><div><a href="https://www.ncl.ucar.edu/Document/Graphics/contour_grids.shtml" target="_blank"><b>https://www.ncl.ucar.edu/Document/Graphics/contour_grids.shtml</b></a></div><div>===</div><div><br></div><div>[1] I believe the station data must be interpolated to a grid.</div><div>[2] If it was just the USA, you could use a USA shapefile and then use <a href="https://www.ncl.ucar.edu/Document/Functions/Built-in/gc_inout.shtml" target="_blank"><b>gc_inout </b></a><br></div><div><br></div><div><a href="https://www.ncl.ucar.edu/Document/Functions/Built-in/gc_inout.shtml" target="_blank"><b>gc_inout</b></a><br>
<a href="https://www.ncl.ucar.edu/Applications/Scripts/ARPEGE_BB_Greenland_mask.ncl" target="_blank">ARPEGE_BB_Greenland_mask.ncl</a><br>
<a href="https://www.ncl.ucar.edu/Applications/Scripts/Germany_coastal_counties_DEU_adm.ncl" target="_blank">Germany_coastal_counties_DEU_adm.ncl</a><br>
<a href="https://www.ncl.ucar.edu/Applications/Scripts/Katrina_circle.ncl" target="_blank">Katrina_circle.ncl</a><br>
<a href="https://www.ncl.ucar.edu/Applications/Scripts/Katrina_circle_hist.ncl" target="_blank">Katrina_circle_hist.ncl</a><br>
<a href="https://www.ncl.ucar.edu/Applications/Scripts/mask_9.ncl" target="_blank">mask_9.ncl</a> (<a href="https://www.ncl.ucar.edu/Applications/mask.shtml#ex9" target="_blank">masking</a>)<br>
<a href="https://www.ncl.ucar.edu/Applications/Scripts/shapefile_mask_data_mod.ncl" target="_blank">shapefile_mask_data_mod.ncl</a><br>
<a href="https://www.ncl.ucar.edu/Applications/Scripts/shapefile_utils.ncl" target="_blank">shapefile_utils.ncl</a><br>
<a href="https://www.ncl.ucar.edu/Applications/Scripts/shapefiles_13.ncl" target="_blank">shapefiles_13.ncl</a> (<a href="https://www.ncl.ucar.edu/Applications/shapefiles.shtml#ex13" target="_blank">Shapefiles</a>)<br>
<a href="https://www.ncl.ucar.edu/Applications/Scripts/shapefiles_5.ncl" target="_blank">shapefiles_5.ncl</a> (<a href="https://www.ncl.ucar.edu/Applications/shapefiles.shtml#ex5" target="_blank">Shapefiles</a>)<br>
<a href="https://www.ncl.ucar.edu/Applications/Scripts/shapefiles_9.ncl" target="_blank">shapefiles_9.ncl</a> (<a href="https://www.ncl.ucar.edu/Applications/shapefiles.shtml#ex9" target="_blank">Shapefiles</a>)</div><div><br></div><div>Unfortunately, you have stations in the Gulf of Mexico and off the California coast. Those would be eliminated.</div><div>[3] <a href="https://www.ncl.ucar.edu/Document/Functions/Built-in/triple2grid.shtml" target="_blank"><b><span style="font-family:verdana,sans-serif">tripletgrid</span>_Wrap</b></a> or <a href="https://www.ncl.ucar.edu/Document/Functions/Contributed/obj_anal_ic_Wrap.shtml" target="_blank"><b>obj_anal_ic_Wrap</b></a> may be your best options.</div><div><br></div><div>Raster or Contour ... your choice</div><div><br></div><div>Keep in mind the short term precipitation is not smoothly distributed. Even for a month, it can be highly 'fractal', especially, summer month precipitation. Hence, 'pretty' may not be achievable.</div><div><br></div><div>Attached is a test script which uses <b>obj_anal_ic_Wrap</b>. It shows the distribution using raster and (default) contouring. It is your responsibility to player with different contour levels and (say) <i><b>rscan </b></i>values. Gray areas had no interpolated values.<br></div><div><br></div><div>Good luck<br></div><div><b><br></b> </div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Nov 25, 2019 at 10:29 AM Wensong Weng via ncl-talk <<a href="mailto:ncl-talk@ucar.edu" target="_blank">ncl-talk@ucar.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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Dear NCL Group,</p>
<p style="margin-top:0px;margin-bottom:0px;color:rgb(29,34,40);font-family:"Helvetica Neue",Helvetica,Arial,sans-serif;font-size:13px;text-align:left;background-color:rgb(255,255,255)">
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I am using the gsn_csm_contour_map function to make a contour plot for the precipitation, see the attached. However, there are lots of un-wanted ‘noises’ outside of CONUS (no data). The data is a one dimension array with unstructured grids. How can I get rid
of those ‘noises’ and only draw the contour map over the CONUS.</p>
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Your help is greatly appreciated,</p>
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Wensong Weng</p>
<p style="margin-top:0px;margin-bottom:0px;color:rgb(29,34,40);font-family:"Helvetica Neue",Helvetica,Arial,sans-serif;font-size:13px;text-align:left;background-color:rgb(255,255,255)">
York Univ.</p>
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