[ncl-talk] Polar plots - Actual pole / Latitudes ?

[Adam Phillips]

Hi Helen,
To add on to Rick's response, I agree that this looks like your grid does
not have a pole point. Assuming  that's the case, there is a function that
will add pole points to a grid that doesn't have them:
https://www.ncl.ucar.edu/Document/Functions/Shea_util/add90LatX.shtml

I do not have any experience with this function but a quick test here
suggests that it may do what you want. Note that to use the function the
latitude dimension has to be the rightmost dimension, and that you will
need to reorder your dimensions when you go to plot the new data array so
that the longitude dimension is the rightmost dimension.

Hope that helps. If you have any further questions please post to ncl-talk.
Adam


On Thu, Jan 18, 2018 at 10:01 AM, Rick Brownrigg via ncl-talk <
ncl-talk at ucar.edu> wrote:

> Hi Helen,
>
> To you second question:  it looks like the resource "mpGridLatSpacingF"
> controls the latitude grid. The default is 15-deg, which checks out with
> your plot. I don't know of a way to label lats on a polar plot, and none of
> our examples show this.
>
> As for the 1st question, I still think that perhaps your data does not
> extend all the way to the pole (can you confirm?), and what we are seeing
> that looks like a marker is actually blank background along with remnants
> of the dashed longitude grid. If you look closely at that grid, all the
> lines except the 0,90,180,270, stop at the 75th latitude line, whereas
> those 4 continue on to the pole. The dashed nature of the lines makes it
> look like a tick-mark. In any case, if the data does not extend all the way
> to 90-deg, the plotting routines will not interpolate, and so you'll need
> to find some other means to interpolate the data across the pole before
> plotting.  I'm not really expert at this.
>
> I hope that helps,
> Rick
>
> On Thu, Jan 18, 2018 at 6:38 AM, HELEN PARISH via ncl-talk <
> ncl-talk at ucar.edu> wrote:
>
>> As requested, I am attaching a plot to illustrate what the issues are. As
>> you can see, it looks like the data should be present over the pole itself,
>> but seems to be overlaid by some kind of pole marker.
>>
>> Also, I am unable to tell what the latitudes are on the plot.
>>
>> Thanks,
>> Helen.
>>
>> On Tue, Jan 16, 2018 at 9:39 PM, HELEN PARISH <hparish at ucla.edu> wrote:
>>
>>> a couple of important questions:
>>>
>>> 1) How can I make a polar plot that has the data at the actual pole ?.
>>> By default the plotting software seems to put a white circle with a cross
>>> inside at the pole. However, it is clear from the appearance of the data
>>> right next to the pole that data could easily be interpolated right over
>>> the pole. Could you please tell me how to put data on the pole, rather than
>>> the white circle with the cross in it ?.
>>>
>>> 2) What are the latitudes plotted on the polar plot be default ?. There
>>> appear to be 6 dashed division lines between whatever the outermost
>>> latitude is and the pole. Are these 15 degree latitude bands ?. Or are
>>> these 10 degree latitude bands and it does not plot all the way from the
>>> pole to the equator ?. Is there a way to label the latitudes on the polar
>>> plot so you know what you are looking at ?.
>>>
>>> Thanks,
>>> Helen.
>>>
>>
>>
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-- 
Adam Phillips
Associate Scientist,  Climate and Global Dynamics Laboratory, NCAR
www.cgd.ucar.edu/staff/asphilli/   303-497-1726

<http://www.cgd.ucar.edu/staff/asphilli>
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