[ncl-talk] Adding a line on a map with additional conditions

[Lyndz]

Dear NCL-experts.

I am plotting the potential temperature gradient and I want to:

[1] Extract the location (lat-lon points) along a region of minimum
temperature gradient.
[2] Save the output of [1] to a text file
[3] Draw a line over the region with minimum potential temperature gradient.

The desired output is as shown in the attached figure (test_ncl.jpg).

The file that I am using can be accessed in the following link:
https://www.dropbox.com/s/epkk2jtwis5sfuc/pottemp_gradient_jan_2017.nc?dl=0

I am also attaching my script in generating the plot.

Any suggestions on how to do this correctly in NCL?
I'll appreciate any help regarding this.

Sincerely,

Lyndz
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