Re: wmstnm improvements

From: Fred Clare <fredclare_at_nyahnyahspammersnyahnyah>
Date: Tue Dec 15 2009 - 01:09:01 MST

On Dec 13, 2009, at 6:26 AM, Bolli Palmason wrote:

> Dear NCL users,
> thanks to NCAR for a very nice graphics package!

Thanks for the comment.
> I'm using the wmstnm function to plot SYNOP data and there are two
> things that could improve (I'm using UNT 1 - metric):
> 1. The visibility should be the numbers from the SYNOP code, not
> translated to km. 70 in SYNOP code should be plotted as 70, not 20
> (km).

In implementing wmstmn I encoded the data as per the SYNOP Data Format
(FM-12) as described at:

which indicates visibility is encoded in km. What source for SYNOP
codes are you using? Since wmstnm has been in our package for over
fifteen years with the visibilities coded in km and yours is the first
suggestion to code as per another scale, I am hesitant to change the
code at this time. I could define a user-settable parameter that
would control how visibility is encoded. In the meantime, you could
define a function that converts km to the SYNOP codes you want to use--
this would not be precise, but it would be close.
> 2. The dots/stars for rain/snow should be bigger or different size, it
> is hard to see the difference.

I can see that at small sizes there could be difficulty in
distinguishing these symbols. These symbols were digitized from scaled
up symbols that appear in NOAA's publication "Explanation of the
Weather Map." Are the dots/stars for rain/snow the only ones you find
that are causing confusion? Again, I am hesitant to redigitize those
as to make them inconsistent with the sizes of dots and stars used
elsewhere, and redigitizing all of the dots and stars would be a bit
of bother. Also, the spacings would have to be readjusted. What
sizes do you normally plot these symbols at and what is your output
device? Plotting the symbols to a Postscript file and printing seems
to resolve the symbols fairly well for me. All of these characters
are drawn as lines and filled areas and not as raster images scaled
for device-specific resolutions; that could definitely cause confusion
on lower-resolution output devices.
> Hope NCAR considers these changes, must be bothering others also :)

You are the first to bring these issues up, but I can see your point
and will file this for future reference.

Thanks for your input.

Fred Clare

> Best regards,
> Bolli
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Received on Tue Dec 15 01:09:27 2009

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