[ncl-talk] writing netCDF file

[Mary Haley]

Dear Dipti,

I'm sorry, but I missed that you had a second question imbedded in this
email.

Were you able to get the metadata added to "wc"?

The reason it doesn't have metadata like "var" is because when you do a
calculation and assign it to a variable that doesn't exist:

wc=(wv/(-9.8*denv))

then "wc" will not inherit any metadata from wv or denv except the
_FillValue attribute.

In order to get metadata, you either need to do a direct variable copy
first, so that "wc" gets metadata before doing the calculation:

wc=wv   ; Trick to copy metadata from wv to wc (values also get copied)
wc=(wc/(-9.8*denv))

or you can use copy_VarMeta:

wc=(wv/(-9.8*denv))
copy_VarMeta(wv,wc)   ; copy wv's metadata to wc

In either case, you should update the long_name/standard_name and units
attributes of wc to correctly reflect what they are.

--Mary



On Thu, Jun 29, 2017 at 5:12 PM, Dipti Sharma <sdipti596 at gmail.com> wrote:

> Hi Mary,
>
> Thank you. It worked now. I also made file name little shorter then that
> worked.
>
> ncdf=addfile("/Users/Downloads/New\ folder/MERRA_19950830.nc","c")
> but one thing, when I do printVarSummay(var) I get the var info with
> 2dimensions
>
> Number of Dimensions: 2
> Dimensions and sizes:   [time | 8] x [lev | 72]
> Coordinates:
>             time: [0..1260]
>             lev: [   1..  72]
> Number Of Attributes: 13
>   lon : -112.5
>   lat :   42
>   valid_range : ( -1e+15, 1e+15 )
>   vmin :        -1e+15
>   vmax :        1e+15
>   standard_name :       air_density
>   add_offset :   0
>   scale_factor :         1
>   fmissing_value :      1e+15
>   missing_value :       1e+15
>   _FillValue :  1e+15
>   units :       kg m-3
>
> But for wc, when I do printVarSummay(wc)
> Variable: wc
> Type: float
> Total Size: 2304 bytes
>             576 values
> Number of Dimensions: 2
> Dimensions and sizes:   [8] x [72]; There is different format so how to
> get this like ' [time | 8] x [lev | 72]'?
>
> Coordinates:
> Number Of Attributes: 1
>   _FillValue :  1e+15
> (0)
> (0)     min=-0.0658635   max=0.0909946
>
> ALSO, my necdf file is not looking with correct attributes,
>
> netcdf file:/C:/Users/Downloads/New%20folder/MERRA2_19950830.nc {
>   dimensions:
>     ncl0 = 8; should be time=8;
>     ncl1 = 72;lev=72; etc.
>     ncl2 = 8;
>     ncl3 = 72;
>   variables:
>     int time(ncl0=8);
>
>     double lev(ncl1=72);
>
>     float data2(ncl2=8, ncl3=72);
>
> }
>
>
> Thank you so much again.
>
> Dipti
>
>
>
> On Thu, Jun 29, 2017 at 11:49 AM, Mary Haley <haley at ucar.edu> wrote:
>
>> Hi Dipti,
>>
>> I'm not sure that addfile can recognize Windows type of directory paths
>> with "C:\....".
>>
>> Try using UNIX-style paths:
>>
>> ncdf=addfile("/Users/Downloads/New\ folder/MERRA2_200.inst3_3d_asm
>> _Nv.19950830.nc <http://merra2_200.inst3_3d_asm_nv.19950830.nc/>","c")
>>
>> Note that I used forward slashes ('/') instead of backward slashes
>> ('\').  However, since you have a space in one of your directory
>> names----"New folder"---I put a backward slash in front of the space, just
>> in case.
>>
>> --Mary
>>
>>
>> On Wed, Jun 28, 2017 at 5:55 PM, Dipti Sharma <sdipti596 at gmail.com>
>> wrote:
>>
>>> Dear NCL,
>>>
>>> I am trying to write netCDF file for selected variable (wc, the vertical
>>> velocity here in this example) from MERRA-2 wind data. However, I always
>>> get an error message saying that
>>>  " fatal:Could not create (C:\Users\Downloads\New folder\
>>> MERRA2_200.inst3_3d_asm_Nv.19950830.nc)
>>>
>>> Could someone please help me how to write the output file in netCDF. I
>>> want to have wc (time,lev) 2D data from 4D (time, lev,lat,lon). I just want
>>> the data at 1 location (1 lat and 1 lon).
>>>
>>> Thank you very much in advance for your help.
>>>
>>> Regards,
>>>
>>> Dipti
>>>
>>> Attached is the script that I used to read the data.
>>>
>>>
>>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
>>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
>>>
>>> ; setfileoption("nc", "FileStructure", "Advanced")
>>>
>>> fn = "C:\Users\Downloads\New folder\MERRA2_200.inst3_3d_asm
>>> _Nv.19950830.nc4"
>>> fn1 = "C:\Users\Downloads\New folder\MERRA2_200.inst3_3d_gas
>>> _Nv.19950830.nc4"
>>>
>>>  fi = addfile(fn, "r")
>>> fi1= addfile(fn1, "r")
>>>
>>> ; setfileoption("nc", "Format",  "NetCDF4Classic")
>>>
>>>  printVarSummary(fi)
>>> ;print(fi)
>>>
>>>  time = fi->time
>>>  lev = fi->lev
>>>  lat = fi->lat
>>>  lon = fi->lon
>>>  u = fi->U;(:,:,269,101)
>>>  v = fi->V;(:,:,269,101)
>>>  w=fi->OMEGA;(:,:,269,101)
>>>  p=fi->PL;(:,:,269,101)
>>> den=fi1->AIRDENS;(:,:,269,101)
>>> uh=u(:,:,269,101)
>>> uv=v(:,:,269,101)
>>> wv=w(:,:,269,101)
>>> pv=PL(:,:,269,101)
>>> denv=den(:,:,269,101)
>>> ;printVarSummary(u)
>>> printVarSummary(denv)
>>> printVarSummary(wv)
>>> printMinMax(wv,True)
>>> ;calculate vertical velocity
>>> wc=(wv/(-9.8*denv))
>>> printVarSummary(wc)
>>> printMinMax(wc,True)
>>> wc!0="time"
>>> wc!1="lev"
>>> ;wc!2="lat"
>>> ;wc!3="lon"
>>> datad = wc;(time|:,lev|:)
>>> printVarSummary(datad)
>>>
>>> ;Writeout new netCDF file
>>>
>>> wc&time = time
>>> wc&lev = lev
>>> ncdf=addfile("C:\Users\Downloads\New folder\MERRA2_200.inst3_3d_asm
>>> _Nv.19950830.nc","c")
>>> ncdf->time= (/time/)
>>> ncdf->lev=  (/lev/)
>>> ncdf->data=(/datad/)
>>> return
>>> end
>>>
>>>
>>>
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>>>
>>
>
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