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no lat/lon under desired variable

Added by Vicki Lindsay over 7 years ago

I have several NetCDF files from the same source, but they are in different formats. I had no problem working with year2013 data (NO2.year.avg.2013.nc) where the variable NO2 has lat/lon. But for year2010 data (NO2.year.avg.2010.nc) the lat/lon are stored as x and y. When I project the data in ArcGIS no projection is recognised. My question is how can I change the year2010 data to the same format of 2013 using cdo (i.e. with 'correct' lat and lon built under variable NO2), so I can project it correctly in places ArcGIS?

*NO2.year.avg.2010*
4 variables (excluding dimension variables):
        double time_bnds[bnds,time]   
        float lon[x,y]   
            units: degrees_east
        float lat[x,y]   
            units: degrees_north
        float NO2[x,y,time]   
            units: ug/m3
            _FillValue: -999
            missing_value: -999

     4 dimensions:
        time  Size:1   *** is unlimited ***
            standard_name: time
            bounds: time_bnds
            units: day as %Y%m%d.%f
            calendar: proleptic_gregorian
            axis: T
        bnds  Size:2
        x  Size:491
        y  Size:344

*NO2.year.avg.2013*
2 variables (excluding dimension variables):
        double time_bnds[bnds,time]   (Chunking: [2,1])  
        float NO2[lon,lat,time]   (Chunking: [701,401,1])  
            long_name: NO2
            units: ug
            _FillValue: -999
            missing_value: -999

     4 dimensions:
        time  Size:1   *** is unlimited ***
            standard_name: time
            long_name: time at end of period
            bounds: time_bnds
            units: day as %Y%m%d.%f
            calendar: proleptic_gregorian
            axis: T
        bnds  Size:2
        lon  Size:701
            standard_name: longitude
            long_name: longitude
            units: degrees_east
            axis: X
        lat  Size:401
            standard_name: latitude
            long_name: latitude
            units: degrees_north
            axis: Y
Download all files
NO2.year.avg.2010.nc (1.93 MB) NO2.year.avg.2010.nc
NO2.year.avg.2013.nc (1.11 MB) NO2.year.avg.2013.nc

Replies (4)

RE: no lat/lon under desired variable - Added by Vicki Lindsay over 7 years ago

sinfon for the data:

*NO2.year.avg.2010*
File format : NetCDF2
    -1 : Institut Source   T Steptype Levels Num    Points Num Dtype : Parameter name
     1 : unknown  unknown  c instant       1   1    168904   1  F32  : lon           
     2 : unknown  unknown  c instant       1   1    168904   1  F32  : lat           
     3 : unknown  unknown  v instant       1   1    168904   1  F32  : NO2           
   Grid coordinates :
     1 : generic                  : points=168904 (491x344)
   Vertical coordinates :
     1 : surface                  : levels=1
   Time coordinate :  1 step
  YYYY-MM-DD hh:mm:ss  YYYY-MM-DD hh:mm:ss  YYYY-MM-DD hh:mm:ss  YYYY-MM-DD hh:mm:ss
  2010-07-02 11:30:00

*NO2.year.avg.2013*
File format : NetCDF
    -1 : Institut Source   T Steptype Levels Num    Points Num Dtype : Parameter name
     1 : unknown  unknown  v instant       1   1    281101   1  F32  : NO2           
   Grid coordinates :
     1 : lonlat                   : points=281101 (701x401)
                              lon : -25 to 45 by 0.1 degrees_east
                              lat : 30 to 70 by 0.1 degrees_north
   Vertical coordinates :
     1 : surface                  : levels=1
   Time coordinate :  1 step
  YYYY-MM-DD hh:mm:ss  YYYY-MM-DD hh:mm:ss  YYYY-MM-DD hh:mm:ss  YYYY-MM-DD hh:mm:ss
  2013-07-02 11:30:00

RE: no lat/lon under desired variable - Added by Ralf Mueller over 7 years ago

the two files have completely different grids: 2010-dataset is curvilinear, 2013 is a regular lonlat grid, both cover Europe. you can interpolate the curvilinera grid into the other one with

  • add the coordinates attribute to the input 
    cdo setattribute,NO2@coordinates="lat lon" NO2.year.avg.2010.nc NO2.year.avg.2010--.nc
  • use bilinear interpolation onto the target grid from 2013
    cdo remapbil,NO2.year.avg.2013.nc NO2.year.avg.2010--.nc NO2.year.avg.2010-LONLAT.nc

I noticed, that the 2010 domain is slightly smaller than the one from 2013

hth
ralf

NO2.year.avg.2010-LONLAT.nc (1.08 MB) NO2.year.avg.2010-LONLAT.nc

RE: no lat/lon under desired variable - Added by Vicki Lindsay over 7 years ago

Saved my day! Thank you!!!

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