[pyngl-talk] Updates for using Pyngl

[Mary Haley]

Hi Xiaoni,

The image looks to me like the land is getting filled in and covering up
the filled contours underneath the map.

Please try setting:

res.mpLandFillColor = "transparent"
res.mpInlandWaterFillColor = "transparent"


I've updated the geodesic example at so you can see the structure of the
"cx" and "cy" grid:

http://www.ncl.ucar.edu/Applications/geodesic.shtml

Click on the second image of the first example:

http://www.ncl.ucar.edu/Applications/geodesic.shtml

Does your ISCCP NetCDF file have any variables on it that look like they
might define grid corners or some kind of cell bounds?

If you can provide us with a copy of your file, or else the output from the
following command,

ncl_filedump *yourfile*.nc

then we can have a look to see if there's anything that might help.

"yourfile.nc" needs to be replaced with the name of your NetCDF file.

---Mary



On Tue, Oct 25, 2016 at 9:41 AM, Xiaoni Wang <xiaoni.wang at obspm.fr> wrote:

> Hi Mary,
>      Thank you very much for your prompt response and helpful information
> !
>
> 1)  in order to plot non-ocean part, I added the following lines in my
> code.
> res.mpFillOn = True
> res.mpOceanFillColor = "white"
>
> The resulting figure still contains ocean. Then I added
> res.mpFillDrawOrder = "PostDraw"
> ​
> This time, the ocean part disappeared. But the color scale is greatly
> changed in the figure. I attach two figures in the below to show their
> effects. isccp_19V.000001.png with PostDraw added,
> and isccp_19V.000001.png.old without Postdraw.
>
> How can I have the same color as isccp_19V.000001.png.old, but without
> ocean ?
>
>
>
> 2)  I also looked at how to fill the small islands in your examples. There
> are something that I would like to clarify.
>      It seems that , we need the latitude/longitude of grid center, and
> also information about grid corner, in order to constrain the interpolation.
>      In my case, between any two grids, the distance between their center
> is 0.25 degree in latitude, and varying in longitude. So I have the
> distance between two grid center in latitude and longitude (in degree).  My
> question is : how to use them ? The geodesic example just read in  the
> corner_lat/lon, but are they the latitude/longitude of the 4 corners of a
> grid ? if so, which corder is the first one, and in which order are they
> organized ? (In the mpas example, they seem to read in latVertex and
> lonVertex and they define latvoc/lonvoc. Yet I have the same question….)
>
>
> Thank you again !!
>
> Best wishes,
>
> Xiaoni
>
>
>
>
>
>
>
>> 2) Over small islands, the interpolation method also produced some
>> effects (see large yellow areas on the ocean in figure
>> isccp_19V.00001.png). Again I do not need the ocean around the island, just
>> the results over (small) islands.
>>
>
> ​This is simply an artifact of having a few values surrounded by a lot of
> missing values.  In order to plot data like this correctly, you need to
> have some kind of cell boundary or grid corner information, so the
> interpolation stays within these bounds.
>
> If you look at our NCL examples for geodesic and MPAS grids, they set
> these two special resources:
>   res at sfXCellBounds        = cx
>   res at sfYCellBounds        = cy
> ​which were read off a file, and are usually dimensioned something like N
> x 4 or N x 3 where N is the number of cell centers, and the 3 or 4
> represents the number of vertices of a polygon that surrounds each cell
> center.
>
> You can see the NCL code for these examples at:
>
> http://www.ncl.ucar.edu/Applications/geodesic.shtml
> http://www.ncl.ucar.edu/Applications/mpas.shtml  (see example
> mpas_cell_3.ncl)
>
>
>
>
>
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