[ncl-talk] Data Extraction

[Dennis Shea]

Your question is very general ... no specifics. Hence, it is hard to
respond.

[1]
It is *your responsibility* to learn the language. When ncl-talk people see
"can you guide me" , we have found that 'we' (ncl-talk) does most, if not
all the work. Hence, people afre reluctant to respond. We want to help but
we have our own jobs to do.

[2]
Please see the excellent tutorials  created by *Karin Meier-Fleischer*
and *Michael
Böttinger* of DKRZ <https://www.dkrz.de/> (Deutsches Klimarechenzentrum).
     http://www.ncl.ucar.edu/Document/Manuals/
In particular, it would be beneficial for you to do some of the exercises.

[3]
An example of "data extraction"

   [a] Examine the file's contents

        %>  ncl_filedump   TES-Aura_L2-O3-Nadir_Megacity_ v006_Litev08.nc
| less
      or
         %>  ncdump -h   TES-Aura_L2-O3-Nadir_Megacity_ v006_Litev08.nc  |
less

[snip]
       float averagecloudeffopticaldepth(grid_targets) ;
                averagecloudeffopticaldepth:long_name = "average cloud
effective optical depth" ;
                averagecloudeffopticaldepth:units = "" ;
                averagecloudeffopticaldepth:_fillvalue = -999.f ;
                averagecloudeffopticaldepth:missing_value = -999.f ;
[snip]
        int cityindex(grid_targets) ;
                cityindex:long_name = "city index:  [Los Angeles, Houston,
New York City, Mexico City, Sao Paulo, Buenos Aires, Pa
ris, Istanbul, Lagos, Beijing, SW China, Shenzhen, Tokyo, Bangkok, Dhaka,
Delhi, Mumbai, Kolkata, Karachi]" ;
                cityindex:units = "" ;
                cityindex:_fillvalue = "" ;
                cityindex:missing_value = "" ;
[snip]


   [b]  Say, you want Lagos: NCL indexing starts at 0 ... hence index 8

   [b] Select a variable and in a script ...

       diri = "./"     ; directory with data file(s)
       fili   = "TES-Aura_L2-O3-Nadir_Megacity_ v006_Litev08.nc"
       pthi = diri+fili

       f = addfile(pthi, "r")
       aceod = f->averagecloudeffopticaldepth    ; all 'grid_targets'
       printVarSummary(aceod)
       printMinMax(aceod)

or

      i = 8
      aceod_Lagos = f->averagecloudeffopticaldepth(i)
      printVarSummary(aceod_Lagos)
      printMinMax(aceod__lagos


Good luck


On Thu, Feb 23, 2017 at 2:20 AM, Najib Yusuf <najibgal at yahoo.com> wrote:

> Dear all,
> I need some more help please. Can you guide me to Data variable extraction
> and also data (measurement and model output) comparison templates?
>
> I will appreciate your elderly advise. Thank you
>
> Najib
>
>
> On Saturday, February 18, 2017 4:57 PM, Dennis Shea <shea at ucar.edu> wrote:
>
>
> The file you sent has a .rc extension. This is not a recognized file
> extension. I changed it to a .nc extension
>
> %> mv TES-Aura_L2-O3-Nadir_Megacity_ v006_Litev08.rc
> TES-Aura_L2-O3-Nadir_Megacity_ v006_Litev08.nc
>
> Then, I used
>
> %> ncdump -h TES-Aura_L2-O3-Nadir_Megacity_ v006_Litev08.nc >&!
> out_630.TES_Nadir
>
> The output (out_630.TES_Nadir) is attached.
>
> ============================== ======
> NCL 6.3.0
>
> %> ncl_filedump TES-Aura_L2-O3-Nadir_Megacity_ v006_Litev08.nc | less
>
> NCL reads the file just fine. However, by netCDF rule, the _FillValue
> associated with a variable should match the type of the variable with which
> it is associated.
>
>       variable (float); _FillValue (float)
>       variable (byte); _FillValue (byte)
>       ...etc...
>
> This file sometimes has a mismatch so ncl_filedump (unlike ncdump -h) will
> issue a warning message like
>
> warning:NetOpenFile: MissingToFillValue option set True, but missing_value
> attribute and data variable (city) types differ: not adding virtual
> _FillValue attribute
>
> Actually, this is valuable information. You should be aware of this. The
> TES file is technically not a good netCDF file.
>
> ===
> In an NCL script, you can turn off the warning messages via:
>
> *setfileoption*("nc","*MissingToF illValue*", False)
>
> f = addfile("TES-Aura_L2-O3-Nadir_ Megacity_v006_Litev08.nc", "r")
>
>
>    https://www.ncl.ucar.edu/ Document/Functions/Built-in/
> setfileoption.shtmn
> <https://www.ncl.ucar.edu/Document/Functions/Built-in/setfileoption.shtml>
>
> On Fri, Feb 17, 2017 at 12:53 AM, Najib Yusuf <najibgal at yahoo.com> wrote:
>
> Hello Denish,
>
> [1] TES-Aura_L2-O3-Nadir_ Megacity_v006_Litev08
>
> [2] I tried opening the data "ncdump" it has open but not in readable
> format.
>
> [3] NCL version 6.3.0
>
>
> Najib
>
>
>
> On Thursday, February 16, 2017 4:01 PM, Dennis Shea <shea at ucar.edu> wrote:
>
>
> re: " ...  but I am having trouble extracting a parameter from TES data."
>
> [1] What type of file: L1B (Nadir), L2 (Nadir and Ancillary), and L3
> (Gridded)?
> [2] Can you please show what you have tried?
> [3] What version of NCL are you using?
>      %>  ncl -V
>
>
>
>
>
>
> On Thu, Feb 16, 2017 at 1:54 AM, Najib Yusuf <najibgal at yahoo.com> wrote:
>
> Dear all,
> I want to compare TES data with model output using NCL but I am having
> trouble extracting a parameter from TES data.
> Kindly assist me on how to achieve this.
>
> Thank you.
>
>
> Najib Yusuf
> Centre for Atmospheric Research
> Anyigba. Nigeria.
> +234 80 371 4158
>
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