# [ncl-talk] Problem with overlay plot

Mary Haley haley at ucar.edu
Fri Aug 22 08:21:09 MDT 2014

```Ipsita,

I took this offline to ask Dennis about it. Here's what he responded:

There is no function to convert height to pressure.

[1] *If* she had temperature and surface geopotential she could use:

https://www.ncl.ucar.edu/Document/Functions/Built-in/hydro.shtml

[2] If she does not have the above, there is no existing equation(s) that
can
be used.

[3] A poor-man (poor-woman) approach would be to use

https://www.ncl.ucar.edu/Document/Functions/Built-in/stdatmus_z2tdp.shtml

This maps the height into the U.S. Standard Atmosphere climatological
height.

---
z    = (/0, 100, 500, 7500, 25000, 84000 /)
tdp = stdatmus_z2tdp(z)    ; ===> tdp(3,6)
print(tdp(0,:)+"  "+tdp(1,:)+"   "+tdp(2,:))

---

0)      15        1.225       1013.25
(1)     14.35   1.21328   1001.29
(2)     11.75   1.16727     954.608
(3)     -33.75  0.556623   382.514
(4)     -51.5    0.0394658    25.1102
(5)     -84.5    8.05098e-06   0.00435981

--Mary

On Wed, Aug 20, 2014 at 10:10 PM, Ipsita Putatunda <
ipsita.putatunda at gmail.com> wrote:

> Hi Mary,
>     Thanks for your suggestions. I have modified my script as per your
> suggestion, but the issue is LH4 level dimension is in Km unit whereas,
> wscale level unit is in hpa. If I am trying to select the levels same for
> both the variable (say 25 levels for LH4 and for wscale) then both the plot
> is not covering same height.
> Is there any way to solve this isuue? Can I convert my data variable LH4
> from Km to hpa or wscale hpa to Km in ncl?
>
> Thanks,
> Ipsita
>
>
> On Wed, Aug 20, 2014 at 12:27 AM, Mary Haley <haley at ucar.edu> wrote:
>
>> Ipsita,
>>
>> Thanks for providing your code and data.
>>
>> I'm a bit confused by the code, because the "LH4" variable purposely has
>> all the metadata stripped off by this command:
>>
>>   LH4=(/L3*24/)
>>
>> You want to preserve metadata, especially coordinate arrays, if you are
>> going to be plotting and/or overlaying variables.
>>
>>    LH4=L3
>>
>> You also want to do this for "wscale":
>>
>>    wscale=W         ; Trick for copying metadata
>>
>>    wscale=W*scale
>>
>> The above two lines could also be done like this:
>>
>>    wscale=W*scale
>>    copy_VarMeta(W,wscale)      ; Copy all metadata from W to wscale
>>
>> Another issue is you are plotting LH4 using "gsn_contour" instead of
>> "gsn_csm_contour". You want to use "gsn_csm_xxxx" scripts where possible,
>> because they examine your variable to check for metadata, and will use that
>> metadata, including coordinate arrays, to correctly plot it.
>>
>> Even with these corrections, the overlay is not going to work properly
>> because your "lev" coordinate array is different in for your LH4 variable
>> than it is for your wscale/U variables.  In order for "overlay" to work,
>> your X/Y coordinate arrays must be in the same data space.
>>
>> For LH4, note that the "lev" values go from 0 to 14:
>>
>> Variable: LH4
>> Type: float
>> Total Size: 164160 bytes
>>             41040 values
>> Number of Dimensions: 2
>> Dimensions and sizes: [lev | 57] x [lon | 720]
>> Coordinates:
>>             lev: [   0..  14]
>>             lon: [-179.75..179.75]
>>
>> For wscale "levels" looks like this:
>>
>> Variable: wscale
>> Type: float
>> Total Size: 72000 bytes
>>             18000 values
>> Number of Dimensions: 2
>> Dimensions and sizes: [levels | 25] x [lon | 720]
>> Coordinates:
>>             levels: [1000.. 100]
>>             lon: [-180..179.5]
>>
>> Finally, you are calling "draw()", but you need to also call "frame(wks)"
>> after the "draw" command so that the graphic is ended properly.
>>
>> Please fix these issues and post to ncl-talk if you continue to have
>> problems.
>>
>> --Mary
>>
>>
>>
>>
>> On Mon, Aug 18, 2014 at 11:12 PM, Ipsita Putatunda <
>> ipsita.putatunda at gmail.com> wrote:
>>
>>> Hi Mary,
>>>      I have tried as per your suggestion to first overlay the plots and
>>> then to attach, but it is not doing as per my requirements. As my data is
>>> from -179 to 179 longitude wise and I want to plot from -30 to -30 that is
>>> why am attaching two plots from -30 to 179  and 179 to -30 longitude. I
>>> finally want to over lay one vector plot and one contour plot. My script
>>> with data files are attached herewith.
>>> Any help will be appreciated.
>>>
>>> Thanks,
>>> Ipsita​
>>>  GLOBAL_SON.nc
>>> ​​
>>>  MERRA_regrid.nc
>>> ​
>>>
>>>
>>> On Thu, Aug 14, 2014 at 9:03 PM, Mary Haley <haley at ucar.edu> wrote:
>>>
>>>> Ipsita,
>>>>
>>>> I'm not exactly sure how you want your final plot to look, but the
>>>> "overlay" procedure really is meant to be used to do simply overlays of
>>>> say, contours on a map, or vectors on contours on a map, etc.
>>>>
>>>> It looks like you are trying to attach some plots via X and/or Y axes,
>>>> and then try to use these as overlays, which won't work. The
>>>> gsn_attach_plots (which is perhaps poorly named) is simply meant to join
>>>> several plots together along a given axis.
>>>>
>>>> My suggestion is to overlay the plots *before* you call
>>>> gsn_attach_plots.
>>>>
>>>> If you continue to have problems, please describe your desired result
>>>> in more detail, and what you are currently getting of your script that
>>>> isn't correct.
>>>>
>>>> As always, it helps if you can provide a full script and your data so
>>>> we can run the script here.
>>>>
>>>> Thanks,
>>>>
>>>> --Mary
>>>>
>>>>
>>>>
>>>> On Wed, Aug 13, 2014 at 1:18 PM, Ipsita Putatunda <
>>>> ipsita.putatunda at gmail.com> wrote:
>>>>
>>>>> Hi,
>>>>>   I want to get an overlay plot of two plots which are created by
>>>>> attached plot. I have tried with overlay function which is not giving my
>>>>> desired plot. I tried with setting vpXF, vpYF for each plot also, but still
>>>>> am not getting overlaid plot. Is attaching plots before overlaying is
>>>>> causing the problem? Plotting part of my script is attached herewith.
>>>>>
>>>>> Thanks,
>>>>> Ipsita
>>>>>
>>>>> _______________________________________________
>>>>> ncl-talk mailing list
>>>>> List instructions, subscriber options, unsubscribe:
>>>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>>>
>>>>>
>>>>
>>>
>>
>
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