<div dir="ltr"><div><div>Is
there an **NCL supported** "method to get the locations of a threshold
value?" <br><br>IE: threshold value => contour level? To my knowledge, the short answer is
"no".<br><div><br></div>I know of no way to retrieve the lat/lon locations of a specific or an arbitrary contour level.<br><br>====<br><br><div><div>This
is a task that is conceptually easy to address. One simple method is to
use linear interpolation. (see attached) However, in practice, there
are issues.<br><br></div><div>Look at the main plot for zonal wind:<br> <a href="http://www.ncl.ucar.edu/Applications/cylineq.shtml" target="_blank">http://www.ncl.ucar.edu/Applic<wbr>ations/cylineq.shtml</a><br><br></div><div>Say, your threshold value is 12.3 m/s.<br><br></div><div>At each longitude, there are one or more '12.3' values looking pole_to_pole.<br><br></div>Choose
-8.0 .... at some longitudes there is no such value while at others,
there are multiple values (closed contours). What to do? How to return
reasonable values?<br><br></div><div>I am attaching a simple scrip and function that uses the <a href="http://uv300.nc" target="_blank">uv300.nc</a> file distributed with NCL.<br></div>You can play with this. Currently, it returns the locations of the 1st encountered threshold value. <br><br></div>If you are looking at (say) the northern hemisphere and there is one 5880gpm contour, it may work for you.<br><br></div>Good luck<br><div><div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Oct 9, 2016 at 10:57 PM, 陈婕 <span dir="ltr"><<a href="mailto:chenj2014@lzu.edu.cn" target="_blank">chenj2014@lzu.edu.cn</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Dear Mr/Mrs,<br>
<br>
I want to get locations of a threshold value. For example, I want to know the locations of 5880gpm contour line at 500hpa. Actually,I only can find the approximate values and their locations from the original grid data. Is there a function for interpolation or a method to get the locations of a threshold value?<br>
<br>
<br>
Best regards,<br>
Jie Chen<br>
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