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[netCDF #FRM-971199]: Quick question about NetCDF or CDL data format

Good afternoon,

Given that pr is indexed by (time, lat, lon), `pr` will vary the slowest along 
the time axis and fastest along the lon axis.  So, I would expect the data to 
correspond with (time,-88.92773,0), (time,-88.927773,1.40625), etc.   That is 
making some assumptions about the file, however.

You can double check this  by passing the `-fc` option to ncdump, e.g. 
`./ncdump -fc [filename]`.  This will generate a C language file with full 
index annotations for each variable; you should be able to inspect the output 
and confirm which values correspond to which indices, which should then inform 
the layout of the data in the cdl file.

I hope this helps,

-Ward



> Hello:
> 
> I downloaded some netcdf data and used ncdump to export to cdl text format. 
> However, I am not sure how the data is arranged in order for me to utilize 
> it. Can you please point me to a site that describes the data layout?
> 
> For instance, given the header lines below (between asterisked lines below), 
> how is the data arranged? Is it by latitude and then longitude or by 
> longitude and then by latitude? So if the first few latitude and longitude 
> values are as follows:
> 
> lat = -88.92773, -87.5387, -86.14147, -84.74239, -83.3426, -81.94247,
> -80.54214, -79.14171, -77.7412, -76.34063, -74.94003, -73.53939,
> 
> lon = 0, 1.40625, 2.8125, 4.21875, 5.625, 7.03125, 8.4375, 9.84375, 11.25,
> 12.65625, 14.0625, 15.46875, 16.875, 18.28125, 19.6875, 21.09375, 22.5,
> 
> Are the first two data points for the variable pr values corresponding to the 
> following latitude, longitude pairs: (-88.92773, 0) and (-88.92773, 1.40625)? 
> Or do they rather correspond to (-88.92773, 0) and (-87,5387, 0).
> 
> I would appreciate guidance on how the data is structured.
> 
> Thanks and best regards.
> Edward
> address@hidden<mailto:address@hidden>
> 254-968-9440
> 
> 
> ****************
> netcdf sresa1b_ncar_ccsm3-example {
> dimensions:
> lat = 128 ;
> lon = 256 ;
> bnds = 2 ;
> plev = 17 ;
> time = UNLIMITED ; // (1 currently)
> variables:
> float area(lat, lon) ;
> area:long_name = "Surface area" ;
> area:units = "meter2" ;
> float lat(lat) ;
> lat:long_name = "latitude" ;
> lat:units = "degrees_north" ;
> lat:axis = "Y" ;
> lat:standard_name = "latitude" ;
> lat:bounds = "lat_bnds" ;
> double lat_bnds(lat, bnds) ;
> float lon(lon) ;
> lon:long_name = "longitude" ;
> lon:units = "degrees_east" ;
> lon:axis = "X" ;
> lon:standard_name = "longitude" ;
> lon:bounds = "lon_bnds" ;
> double lon_bnds(lon, bnds) ;
> int msk_rgn(lat, lon) ;
> msk_rgn:long_name = "Mask region" ;
> msk_rgn:units = "bool" ;
> double plev(plev) ;
> plev:long_name = "pressure" ;
> plev:units = "Pa" ;
> plev:standard_name = "air_pressure" ;
> plev:positive = "down" ;
> plev:axis = "Z" ;
> float pr(time, lat, lon) ;
> pr:comment = "Created using NCL code CCSM_atmm_2cf.ncl on\n",
> " machine eagle163s" ;
> pr:missing_value = 1.e+020f ;
> pr:_FillValue = 1.e+020f ;
> pr:cell_methods = "time: mean (interval: 1 month)" ;
> pr:history = "(PRECC+PRECL)*r[h2o]" ;
> pr:original_units = "m-1 s-1" ;
> pr:original_name = "PRECC, PRECL" ;
> pr:standard_name = "precipitation_flux" ;
> pr:units = "kg m-2 s-1" ;
> pr:long_name = "precipitation_flux" ;
> pr:cell_method = "time: mean" ;
> float tas(time, lat, lon) ;
> tas:comment = "Created using NCL code CCSM_atmm_2cf.ncl on\n",
> " machine eagle163s" ;
> tas:missing_value = 1.e+020f ;
> tas:_FillValue = 1.e+020f ;
> tas:cell_methods = "time: mean (interval: 1 month)" ;
> tas:history = "Added height coordinate" ;
> tas:coordinates = "height" ;
> tas:original_units = "K" ;
> tas:original_name = "TREFHT" ;
> tas:standard_name = "air_temperature" ;
> tas:units = "K" ;
> tas:long_name = "air_temperature" ;
> tas:cell_method = "time: mean" ;
> double time(time) ;
> time:calendar = "noleap" ;
> time:standard_name = "time" ;
> time:axis = "T" ;
> time:units = "days since 0000-1-1" ;
> time:bounds = "time_bnds" ;
> time:long_name = "time" ;
> double time_bnds(time, bnds) ;
> float ua(time, plev, lat, lon) ;
> ua:comment = "Created using NCL code CCSM_atmm_2cf.ncl on\n",
> " machine eagle163s" ;
> ua:missing_value = 1.e+020f ;
> ua:cell_methods = "time: mean (interval: 1 month)" ;
> ua:long_name = "eastward_wind" ;
> ua:history = "Interpolated U with NCL \'vinth2p_ecmwf\'" ;
> ua:units = "m s-1" ;
> ua:original_units = "m s-1" ;
> ua:original_name = "U" ;
> ua:standard_name = "eastward_wind" ;
> ua:_FillValue = 1.e+020f ;
> 
> 
> ******************
> 
> 
> 
> [Title: Tarleton State University]Edward Osei, Ph.D.
> Assistant Professor, Department of Agricultural and Consumer Sciences
> Tarleton State University, Member of The Texas A&M University System
> 1333 W. Washington St. | Stephenville, TX 76402
> 254-968-9440 |www.tarleton.edu/agservices<http://www.tarleton.edu/agservices>/
> 
> 
> 
> 


Ticket Details
===================
Ticket ID: FRM-971199
Department: Support netCDF
Priority: Normal
Status: Closed