# [ncl-talk] Extracting data for a given point from a model output

Dennis Shea shea at ucar.edu
Wed Dec 30 08:39:09 MST 2020

```????  does not return the value of the emflx variable for the desired point
(lat/lon)

Well, what is the "correct value" ?
======

lat = 32.0
lon = 52.0

(0) ==================
(0) n=21   m=8   lat2d(n,m)=31.9429   lon2d(n,m)=51.921   *<====This is the
closest grid point ... pretty close!!!*
(0) ==================

(5) 605628   ymdh=2019010212
(6) 605634   ymdh=2019010218
*(7)* 605640   ymdh=*2019010300    <===  NT=7*
(8) 605646   ymdh=2019010306
(9) 605652   ymdh=2019010312

*YMDH   = 2019010300 *            ; user specified
print("YMDH="+YMDH)
NT     = ind(ymdh .eq. YMDH)
print("NT="+NT+" ymdh(NT)="+ymdh(NT) )

*(0) YMDH=2019010300(0) NT=7 ymdh(NT)=2019010300*
(0) ==================

EMFLX = f->emflx
emflx = EMFLX(NT,n,m)           ; scalar
print("==================")
print( emflx )                 ;  ====

(0) 940.5043

On Wed, Dec 30, 2020 at 8:15 AM Setareh Rahimi <setareh.rahimi at gmail.com>
wrote:

> Dear Dennis,
> Thanks again for your guide. However, after running the code I noticed  tha
> t  Y = f->emflx(NT,n,m)   does not return the value of the emflx variable
> for the desired point (lat/lon).
> Best wishes,
>
> On Tue, Dec 29, 2020 at 3:22 AM Dennis Shea <shea at ucar.edu> wrote:
>
>> I think we have been through this before. There are many *time/date
>> functions.* <https://www.ncl.ucar.edu/Document/Functions/date.shtml>
>>
>>    time  = f->time   ; hours since 1949-12-01 00:00:00 UTC"
>> ; [1]
>>    TIME     = *cd_calendar*
>> <https://www.ncl.ucar.edu/Document/Functions/Built-in/cd_calendar.shtml>(time,
>>    year      = toint( TIME(:,0) )               ; toint strips meta data
>>    month   = toint( TIME(:,1) )
>>    day       = toint( TIME(:,2) )               ; day of month
>>    hour      = toint( TIME(:,3) )               ; hour of day
>>    minute  = toint( TIME(:,4) )
>>    second  = toint( TIME(:,5) )
>>
>>
>> ;[2]
>>   ymdh  =  *yyyymmddhh_time*
>> <https://www.ncl.ucar.edu/Document/Functions/Contributed/yyyymmddhh_time.shtml>(time,
>>
>>   YMDH       = 2019010300
>>   nt        =* ind*
>> <https://www.ncl.ucar.edu/Document/Functions/Built-in/ind.shtml>(ymdh
>> .eq. YMDH)
>> ================================================================
>> A simple script is attached.
>> ================================================================
>>
>> %> ncl setareh.ncl
>>
>>
>> On Mon, Dec 28, 2020 at 3:04 PM Setareh Rahimi <setareh.rahimi at gmail.com>
>> wrote:
>>
>>>
>>> Dear Dennis,
>>> I am not looking for interpotation, temperature was just an example.
>>> Emflx is one of the varibles in the file. I need to know for say
>>> Jan-03-00:00UTC , what is the value of emflx for a specific point .
>>> Best wishes,
>>> On Tue, Dec 29, 2020 at 01:23 Dennis Shea <shea at ucar.edu> wrote:
>>>
>>>> As noted by Eshan, you want interpolation.
>>>>
>>>> Note: Temperature is NOT in the file.
>>>>
>>>>
>>>>   lat2d = f->xlat
>>>>   lon2d = f->xlon
>>>>
>>>>   *printVarSummary* <https://www.ncl.ucar.edu/Document/Functions/Built-in/printVarSummary.shtml>(lat2d)
>>>>   *printMinMax* <https://www.ncl.ucar.edu/Document/Functions/Contributed/printMinMax.shtml>(lat2d, 0)
>>>>   *printMinMax* <https://www.ncl.ucar.edu/Document/Functions/Contributed/printMinMax.shtml>(lon2d, 0)
>>>>
>>>>   stalat = 32.0               ;(/  32.0 ,  17.31, 24.05   /)   ; user specified coordinate pairs
>>>>   stalon = 52.0               ; (/ 52.0 ,-101.00,-92.46   /)
>>>>
>>>>   X = f->mixrat              ; (time, kz, iy, jx)
>>>>   Y = d->ddflx               ; (time, iy, jx)
>>>>
>>>>   x = *rcm2points_Wrap* <https://www.ncl.ucar.edu/Document/Functions/Contributed/rcm2points_Wrap.shtml>(lat2d, lon2d, X, stalat, stalon, 0)
>>>>   y = *rcm2points_Wrap* <https://www.ncl.ucar.edu/Document/Functions/Contributed/rcm2points_Wrap.shtml>(lat2d, lon2d, Y, stalat, stalon, 0)
>>>>
>>>>   print(x)
>>>>
>>>>   print(y)
>>>>
>>>>
>>>> On Mon, Dec 28, 2020 at 12:10 PM Setareh Rahimi <
>>>> setareh.rahimi at gmail.com> wrote:
>>>>
>>>>> Dear Dennis,
>>>>> Many thanks for your response. What I exactly mean is how to extract
>>>>> for example "Temperature variable" value for a specific lat/lon from the
>>>>> output result. For example: what is temperature value for a point at
>>>>> (lat=32, lon 52)?
>>>>> Thanks again
>>>>> Best wishes
>>>>>
>>>>> On Mon, Dec 28, 2020 at 10:17 PM Dennis Shea <shea at ucar.edu> wrote:
>>>>>
>>>>>> *getind_latlon2d *
>>>>>> <https://www.ncl.ucar.edu/Document/Functions/Contributed/getind_latlon2d.shtml>
>>>>>>
>>>>>> A modification of Example 1
>>>>>>
>>>>>>   lat2d = f->xlat
>>>>>>   lon2d = f->xlon
>>>>>>
>>>>>>   *printVarSummary* <https://www.ncl.ucar.edu/Document/Functions/Built-in/printVarSummary.shtml>(lat2d)
>>>>>>   *printMinMax* <https://www.ncl.ucar.edu/Document/Functions/Contributed/printMinMax.shtml>(lat2d, 0)
>>>>>>   *printMinMax* <https://www.ncl.ucar.edu/Document/Functions/Contributed/printMinMax.shtml>(lon2d, 0)
>>>>>>
>>>>>>   lat   = (/  31.0 ,  17.31, 24.05   /)   ; user specified coordinate pairs
>>>>>>   lon   = (/ -86.45,-101.00,-92.46   /)
>>>>>>                                           ; return 2d subscripts
>>>>>>   nm = *getind_latlon2d* (lat2d,lon2d, lat, lon)
>>>>>>
>>>>>>   *print* <https://www.ncl.ucar.edu/Document/Functions/Built-in/print.shtml>(nm)
>>>>>>
>>>>>>   X = f->mixrat              ; (time, kz, iy, jx)
>>>>>>   Y = d->ddflx               ; (time, iy, jx)
>>>>>>
>>>>>>   nt =     .... the index some specified time
>>>>>>
>>>>>>   kl =     ... index
>>>>>>
>>>>>>  do k=0,*dimsizes* <https://www.ncl.ucar.edu/Document/Functions/Built-in/dimsizes.shtml>(lat)-1
>>>>>>      n = nm(k,0)
>>>>>>      m = nm(k,1)
>>>>>>
>>>>>>      x = X(nt,kl,n,m)
>>>>>>      y = Y(nt,n,m)
>>>>>>
>>>>>>      *print* <https://www.ncl.ucar.edu/Document/Functions/Built-in/print.shtml>(lat2d(n,m)+"   "+lon2d(n,m)+"  "+x+"   "+y)
>>>>>>   end do
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Mon, Dec 28, 2020 at 10:16 AM Setareh Rahimi via ncl-talk <
>>>>>> ncl-talk at mailman.ucar.edu> wrote:
>>>>>>
>>>>>>> Dear all,
>>>>>>>
>>>>>>> I need to extract data (it could be any variable like temperature,
>>>>>>> wind ...) for a specific point (say synoptic stations) at a specific day
>>>>>>> and time
>>>>>>>  Yazd-2019_DUST01.2019010100.nc
>>>>>>> ( Jan-03- 00:00 UTC), from a model output (file attached).  I wonder
>>>>>>> how it could be achieved using NCL (any example...) .
>>>>>>>
>>>>>>> I appreciate any suggestion,
>>>>>>> Best wishes,
>>>>>>> --
>>>>>>> S.Rahimi
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> ncl-talk mailing list
>>>>>>> ncl-talk at mailman.ucar.edu
>>>>>>> List instructions, subscriber options, unsubscribe:
>>>>>>> https://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>>>>
>>>>>>
>>>>>
>>>>> --
>>>>> S.Rahimi
>>>>>
>>>>> --
>>> S.Rahimi
>>>
>>>
>
> --
> S.Rahimi
>
>
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