[ncl-talk] An issue with shaded contours in NCL6.4.0

[Mary Haley]

Hi Saji,

This is indeed strange.

Would it be possible for you to include a script and your data so we can
look at the problem here? I especially want to see how the masking is being
done, and I can test it using our 6.5.0 beta version.

You can use our ftp for this, or put the files on your own site:

http://www.ncl.ucar.edu/ftp_files.shtml

Thanks,

--Mary


On Sun, Jun 24, 2018 at 8:02 PM, Saji Hameed <saji.nh at gmail.com> wrote:

> Dear NCL developers,
>
> I would like to report a rather strange issue that appears in version
> 6.4.0 of NCL.
> The issue is related to shaded contours. For me, the issue happens when
> using a dataset for which a mask was applied to "undefine" values over a
> portion of the
> domain.
>
> I have attached four figures to illustrate the issue (two of these were
> made with
> NCL version 6.3.0, and the other two with NCL 6.4.0).
>
> nomask_ncl6.4.png and nomask_ncl6.3.png are plots of rainfall made using
> NCL 6.4.0 and NCL 6.3.0 respectively. There are two panels, with the top
> showing a shaded contour plot, and the bottom a simple contour plot.
> In the cases shown above, all data in the domain were used. There are no
> issues with both the above mentioned plots (they are also identical to each
> other, as expected).
>
> In the next set of plots, I have masked the data over land areas. Once I
> do this, I get
> unexpected colors (white) for some contour levels (between 10 and 12) only
> when using NCL6.4.0.
> There is no issue with NCL6.3.0, which plots the data without any apparent
> problems.
>
> I did note this issue with other plots, but at that time I thought that I
> was overusing colors on my desktop, and my OS could not allocate enough
> colors to NCL. But only today, I figured out that this is seemingly related
> to use of a mask to undefine
> portions of the data domain.
>
> For the time being, I will use NCL6.3.0, and hope that the source of this
> issue
> can be found and fixed.
>
> Best regards,
> saji
>
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