[ncl-talk] How to convert the value of a NetCDF file to zero

[Dennis Shea]

Dave ... As always .... THX
-------------------------
Attached is an *untested* version of my original script with Dave's
suggested modifications. Again, I do not have a local NCL version so I can
not test it.

Note: because the WRF coordinate dimensions are curvilinear, the subscripts
may return a larger area than 1D coordinate variables. You may have to come
up with your own version.

Good Luck

D



On Thu, Jan 25, 2024 at 3:18 PM Dave Allured - NOAA Affiliate via ncl-talk <
ncl-talk at mailman.ucar.edu> wrote:

> Setareh, with simple 1-D coordinate variables, you would easily do this
> with coordinate range subscripting.  Read about that in the NCL ref
> manual.  Here is an example that writes directly into an existing file,
> rather than making a new file.
>
>       f->MSEBIO_ISOP( {0,10}, {10,30} ) = 0
>
> However, the coordinates in your particular file are 3-D, so you have to
> use extra code.  Here is the simplest way.  This is also the slowest, but
> if you are only working with a small amount of data, it is better to keep
> the code simple.  This example also writes directly into the existing
> file.  Not tested:
>
>       lat1 = 0
>       lat2 = 10
>       lon1 = 10
>       lon2 = 30
>
>       do t = 0, ntimes-1
>          do i = 0, nlats-1
>             do j = 0, nlons-1
>                if ( (XLAT(t,i,j) .ge. lat1) .and. (XLAT(t,i,j) .le. lat2) \
>                   .and. (XLONG(t,i,j) .ge. lon1) .and. (XLONG(t,i,j) .le.
> lon2) ) then
>                      f->MSEBIO_ISOP(t,i,j) = 0
>                           ! You can add more variables here
>                end if
>             end do
>          end do
>       end do
>
>
> On Thu, Jan 25, 2024 at 1:04 PM Setareh Rahimi <setareh.rahimi at gmail.com>
> wrote:
>
>> Dear Dave,
>>
>> So many thanks for your help. I just checked it and it worked.
>>
>> May I ask you please to advise me on how to only convert the values of
>> all variables to zero for a specific region and not whole the domain? (for
>> example lat[0,10], and lon[10,30])?
>>
>> Thanks in advance.
>> Kind regards,
>>
>> On Thu, Jan 25, 2024 at 11:18 PM Dave Allured - NOAA Affiliate <
>> dave.allured at noaa.gov> wrote:
>>
>>> The problem is that Dennis's program did not copy the file global
>>> attributes, which contain part of the georeferencing.  Just add this line
>>> near the top of the program, after the line "print (vNames)":
>>>
>>>       copy_VarAtts (f, fout)
>>>
>>>
>>> On Thu, Jan 25, 2024 at 11:07 AM Ehsan Taghizadeh via ncl-talk <
>>> ncl-talk at mailman.ucar.edu> wrote:
>>>
>>>> Dear Setareh,
>>>> I suggest you read the variables from the fout file again. For example,
>>>> if there is a variable named "V10" in fout, you just need to read that
>>>> variable from fout, as follows:
>>>> V10_zero=fout->V10
>>>>
>>>> This V10_zero has the same coordinates as V10 in the original file, but
>>>> its values are zero.
>>>> I hope this is correct.
>>>>
>>>>
>>>> On Thursday, January 25, 2024 at 06:17:12 PM GMT+3:30, Setareh Rahimi
>>>> via ncl-talk <ncl-talk at mailman.ucar.edu> wrote:
>>>>
>>>> Dear Dennis,
>>>> I noticed an issue. When I use the attached script it converts all
>>>> values to zero, but the data is no georefrenced any more. So how can I fix
>>>> this please?
>>>> Thanks in advance.
>>>> Best regards,
>>>>
>>>> S.Rahimi
>>>>
>>>>
>>>> On Sun, Jan 21, 2024 at 18:44 Dennis Shea <shea at ucar.edu> wrote:
>>>>
>>>> Attached is a script that does what you requested.
>>>>
>>>>
>>>> On Sat, Jan 20, 2024 at 6:40 AM Setareh Rahimi via ncl-talk <
>>>> ncl-talk at mailman.ucar.edu> wrote:
>>>>
>>>>
>>>> Dear NCL users,
>>>>
>>>> I have a NetCDF file (attached) that contains some variables. I
>>>> would like to change the values of all variables to zero for all grid
>>>> points. So how can I do this using NCL, please?
>>>>
>>>> This file is an input file for the WRF-Chem model, and I do not want to
>>>> change the format of the file, only want to change the values to zero.
>>>>
>>>> Please kindly advise me in this regard.
>>>>
>>>> Thanks in advance.
>>>> Kind regards,
>>>> --
>>>> S.Rahimi
>>>>
>>>> _______________________________________________
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