[ncl-talk] Vorticity Advection with NCL

Tue May 22 03:08:13 MDT 2018

Good morning,

Thank you very much. There is only one doubt left unanswered: the
*advect_function
*requires a *Gaussian, regular o fixed grid*, but not *rectilinear*. Is
there any relation between them?

Regards,
Lara

2018-05-21 19:21 GMT+02:00 Dennis Shea <shea at ucar.edu>:

> ESMF 37 was
> (a)  interpolating u and v onto a rectilinear grid;
> (b)  calculating divergence using uv2dv_cfd which requires u and v to be
> on a rectilinear grid;
> (c)  interpolating the derived divergence on a rectilinear grid back onto
> the original WRF grid
>
> ---
> In your case:
>
> [1] Interpolate the WRF u, v and relative vorticity to a rectilinear grid
> with as fine [or finer] resoultion as the WRF grid
> [2] Use 'advect_variable' on the rectilinear grid
> [3] interpolate the advected quantity on the rectilinear grid back onto
> the original WRF grid
>
> ---
> Caveat: Technically, on a sphere,  u and v must be interpolated together
> using the 'rotation' angle.
> Why? because the new location has a 'slightly' different orientation
> relative to the pole(s)
>
>   unew        = u*cos(rot) - v*sin(rot)
>   vnew        = u*sin(rot) + v*cos(rot)
>
> The above approach, independently interpolating u and v ignores the
> rotation. It is assumed to be very small.
>
>
>
>
> On Mon, May 21, 2018 at 3:45 AM, Lara Quitián Hernández <
> laraquitianhernandez at gmail.com> wrote:
>
>> Good morning,
>>
>> Thank you so much. Unfortunately, I have some doubts.
>>
>> 1.- I have read the information for Example 37 but I do not understand
>> the need of computing the divergence ("uv2dv_cfd"). I just need my
>> variables on a Gaussian, regular o fixed grid in order to apply the
>> *advect_variable* function
>> 2.- I need to convert my curvilinear WRF grid to a Gaussian, regular o
>> fixed grid. However, in both Examples (29a and 37) a regrid from a WRF grid
>> to a rectilinear grid is carried out. Are those grids (Gaussian, regular o
>> fixed grid) also rectilinear grids?
>> 3.-Do I need to regrid back to the WRF curvilinear grid as it is done in
>> both examples?
>>
>> Thanks in advance.
>>
>> Regards,
>> Lara
>>
>>
>>
>> 2018-05-20 1:10 GMT+02:00 Dennis Shea <shea at ucar.edu>:
>>
>>> NCL has no builtin function to advect a field (eg: vorticity) on a
>>> curvilinear grid (eg: your WRF Grid)..
>>> Maybe ask wrfhelp?
>>>
>>> ===
>>> That said
>>>
>>> https://www.ncl.ucar.edu/Applications/ESMF.shtml
>>> Example 29a
>>> or, maybe better,
>>> Example 37
>>>
>>> outlines a method that might be used for your needs.
>>>
>>> ===
>>> Good luck
>>>
>>>
>>> On Wed, May 16, 2018 at 7:40 AM, Lara Quitián Hernández <
>>> laraquitianhernandez at gmail.com> wrote:
>>>
>>>> Hello,
>>>>
>>>> Thank you. In the case of calculating the horizontal advection for
>>>> *vorticity*, it would be better to use the direct WRF variable ( vo =
>>>> wrf_user_getvar(a,"*avo*",-1)) or define it via different functions:
>>>> https://www.ncl.ucar.edu/Applications/vort.shtml
>>>>
>>>> The only example in the link defines the Vorticity like this:
>>>>
>>>> ;************************************************
>>>> ; calculate vorticity on a Gaussian Grid
>>>> ; scale for visual convenience
>>>> ;************************************************
>>>>   scale = 1.e05
>>>>   vrt   = u                                      ; retain coordinates
>>>>   vrt   = uv2vrG_Wrap(u,v) * scale
>>>>   vrt at long_name = "vorticity"
>>>>   vrt at units     = "scaled"
>>>>
>>>>
>>>> However, my simulations are generated on a Lambert Conformal grid
>>>> projection, not Gaussian one. Does this change the procedure to calculate
>>>> it?
>>>>
>>>> Regards,
>>>> Lara
>>>>
>>>> 2018-05-16 14:28 GMT+02:00 Dennis Shea <shea at ucar.edu>:
>>>>
>>>>> Maybe:
>>>>>
>>>>> https://www.ncl.ucar.edu/Document/Functions/Contributed/adve
>>>>> ct_variable.shtml
>>>>>
>>>>> 'x' would be vorticity
>>>>>
>>>>> Good Luck
>>>>>
>>>>> On Wed, May 16, 2018 at 4:01 AM, Lara Quitián Hernández <
>>>>> laraquitianhernandez at gmail.com> wrote:
>>>>>
>>>>>> Good morning,
>>>>>>
>>>>>> I would like to know if there is a possibility of calculating the
>>>>>> Vorticity Advection with NCL.
>>>>>>
>>>>>> Thanks in advance.
>>>>>>
>>>>>> Regards,
>>>>>> Lara
>>>>>>
>>>>>>
>>>>>> --
>>>>>>
>>>>>>
>>>>>> *Lara Quitián Hernández, PhD Student*
>>>>>> Departamento de Física de la Tierra, Astronomía y Astrofísica
>>>>>> Facultad de Ciencias Físicas
>>>>>> Ciudad Universitaria, Plaza Ciencias, 1
>>>>>> <https://maps.google.com/?q=Ciudad+Universitaria,+Plaza+Ciencias,+1+28040+Madrid.+Spain&entry=gmail&source=g>
>>>>>> 28040 Madrid. Spain
>>>>>> <https://maps.google.com/?q=Ciudad+Universitaria,+Plaza+Ciencias,+1+28040+Madrid.+Spain&entry=gmail&source=g>
>>>>>> Email: lquitian at ucm.es <mlunar at aemet.es>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
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>>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>>
>>>>
>>>> *Lara Quitián Hernández, PhD Student*
>>>> Departamento de Física de la Tierra, Astronomía y Astrofísica
>>>> Facultad de Ciencias Físicas
>>>> Ciudad Universitaria, Plaza Ciencias, 1
>>>> <https://maps.google.com/?q=Ciudad+Universitaria,+Plaza+Ciencias,+1+28040+Madrid.+Spain&entry=gmail&source=g>
>>>> 28040 Madrid. Spain
>>>> <https://maps.google.com/?q=Ciudad+Universitaria,+Plaza+Ciencias,+1+28040+Madrid.+Spain&entry=gmail&source=g>
>>>> Email: lquitian at ucm.es <mlunar at aemet.es>
>>>>
>>>>
>>>
>>
>>
>> --
>>
>>
>> *Lara Quitián Hernández, PhD Student*
>> Departamento de Física de la Tierra, Astronomía y Astrofísica
>> Facultad de Ciencias Físicas
>> Ciudad Universitaria, Plaza Ciencias, 1
>> <https://maps.google.com/?q=Plaza+Ciencias,+1+28040+Madrid.+Spain&entry=gmail&source=g>
>> 28040 Madrid. Spain
>> <https://maps.google.com/?q=Plaza+Ciencias,+1+28040+Madrid.+Spain&entry=gmail&source=g>
>> Email: lquitian at ucm.es <mlunar at aemet.es>
>>
>>
>

-- 

*Lara Quitián Hernández, PhD Student*
Departamento de Física de la Tierra, Astronomía y Astrofísica
Facultad de Ciencias Físicas
Ciudad Universitaria, Plaza Ciencias, 1
28040 Madrid. Spain
Email: lquitian at ucm.es <mlunar at aemet.es>
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