[ncl-talk] geopotential height calculation

Thu Oct 25 09:23:58 MDT 2018

Hi Barry:
I am always kind of cautious using "model-specific" functions like the WRF
suite functions for an other model, especially when the vertical coordinate
system is different. I have not looked at differences in using wrf
functions versus generic functions for vertical interpolation so I cannot
really give you a definitive answer. May be it works just fine.

Cheers,
Laura

On Wed, Oct 24, 2018 at 8:49 AM Barry Lynn <barry.h.lynn at gmail.com> wrote:

> Laura:
>
> There are many wrf_ncl functions I use (plus get user variables).
>
> Is it possible with MPAS to use similar functions?
>
> Barry
>
> On Wed, Oct 24, 2018 at 5:25 PM Laura Fowler <laura at ucar.edu> wrote:
>
>> Zhifeng:
>>
>> I just read your ncl question related to the calculation of the 500 hPa
>> geopotential height in MPAS. Just wanted to let you know that the vertical
>> discretization uses a height coordinate and not sigma (see Klemp (2011) for
>> details on the terrain-following coordinate system used in MPAS).
>>
>> To calculate the 500 hPa geopotential height, you need to use the
>> "height" variable zgrid that is written in the init condition file by
>> default if you have not saved it in a history file. You also need the
>> "pressure" variable which you need to save in your history file. Once you
>> have those 2 fields from your outputs, you can use any of the ncl functions
>> int2p, int2p_n, or int2p_n_Wrap to interpolate you data to the 500 hPa
>> level.
>>
>> Note that MPAS also calculates the geopotential height at several fixed
>> pressure levels too (see the User's guide on how to use the "diagnostics"
>> stream so that you do not have to do that separately.
>>
>>
>> Hope this helps,
>> Laura
>>
>>
>> On Tue, Oct 23, 2018 at 3:13 PM Zhifeng Yang <yangzf01 at gmail.com> wrote:
>>
>>> Hi Adam and Barry,
>>>
>>> Sorry for less information. The vertical grid in MPAS is sigma. The
>>> horizontal grid is Voronoi mesh, unstructured grid. I saw there is a
>>> section in NCL processing MPAS model data. I thought MPAS is very common
>>> while using NCL. Here I attached the output from ncdump and
>>> printVarSummary. There are three types of model output files. diagnos,
>>> history, and restart. I am planning to use history output to calculate the
>>> geopotential height.
>>>
>>> I took a look of several wrf related functions in NCL, e.g.
>>> wrf_interp_3d_z, wrf_interp_2d_xy. However, they are for latitude-longitude
>>> grids, like WRF.
>>>
>>> Zhifeng
>>>
>>>
>>> On Mon, Oct 22, 2018 at 11:02 PM Barry Lynn <barry.h.lynn at gmail.com>
>>> wrote:
>>>
>>>> Just curious -- have your tried the WRF functions?
>>>>
>>>> On Mon, Oct 22, 2018 at 11:53 PM Adam Phillips <asphilli at ucar.edu>
>>>> wrote:
>>>>
>>>>> Hi Zhifeng,
>>>>> I think more information is needed about your data to answer the
>>>>> question. Is your data on hybrid-sigma levels, or some other vertical
>>>>> coordinate? Is your data on an unstructured grid, or some other type? A
>>>>> printVarSummary of your data would also be helpful.
>>>>> Adam
>>>>>
>>>>> On Mon, Oct 22, 2018 at 1:40 PM Zhifeng Yang <yangzf01 at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Hi all,
>>>>>>
>>>>>> I want to get the geopotential height at 500 mb from MPAS model
>>>>>> output. Do we have NCL function to calculate it, or other possible methods?
>>>>>> Thank you
>>>>>>
>>>>>> Zhifeng
>>>>>> _______________________________________________
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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>
>>>>> _______________________________________________
>>>>> ncl-talk mailing list
>>>>> ncl-talk at ucar.edu
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>>>>>
>>>>
>>>>
>>>> --
>>>> Barry H. Lynn, Ph.D
>>>> Senior Associate Scientist, Lecturer,
>>>> The Institute of the Earth Science,
>>>> The Hebrew University of Jerusalem,
>>>> Givat Ram, Jerusalem 91904, Israel
>>>> Tel: 972 547 231 170
>>>> Fax: (972)-25662581
>>>>
>>>> C.E.O, Weather It Is, LTD
>>>> Weather and Climate Focus
>>>> http://weather-it-is.com
>>>> Jerusalem, Israel
>>>> Local: 02 930 9525
>>>> Cell: 054 7 231 170
>>>> Int-IS: x972 2 930 9525
>>>>
>>>> _______________________________________________
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>>
>>
>> --
>>
>> !-------------------------------------------------------------------------------------------------------------
>> Laura D. Fowler
>>
>> Mesoscale and Microscale Meteorology Division (MMM)
>> National Center for Atmospheric Research
>> P.O. Box 3000, Boulder CO 80307-3000
>>
>> e-mail: laura at ucar.edu
>> phone: 303-497-1628
>>
>>
>> !-------------------------------------------------------------------------------------------------------------
>>
>
>
> --
> Barry H. Lynn, Ph.D
> Senior Associate Scientist, Lecturer,
> The Institute of the Earth Science,
> The Hebrew University of Jerusalem,
> Givat Ram, Jerusalem 91904, Israel
> Tel: 972 547 231 170
> Fax: (972)-25662581
>
> C.E.O, Weather It Is, LTD
> Weather and Climate Focus
> http://weather-it-is.com
> Jerusalem, Israel
> Local: 02 930 9525
> Cell: 054 7 231 170
> Int-IS: x972 2 930 9525
>
>

-- 
!-------------------------------------------------------------------------------------------------------------
Laura D. Fowler

Mesoscale and Microscale Meteorology Division (MMM)
National Center for Atmospheric Research
P.O. Box 3000, Boulder CO 80307-3000

e-mail: laura at ucar.edu
phone: 303-497-1628

!-------------------------------------------------------------------------------------------------------------
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