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Version 5.2.7 of the netCDF Operators (NCO) has been released. NCO is an Open Source package that consists of a dozen standalone, command-line programs that take netCDF files as input, then operate (e.g., derive new data, average, print, hyperslab, manipulate metadata) and output the results to screen or files in text, binary, or netCDF formats.

The NCO project is coordinated by Professor Charlie Zender of the Department of Earth System Science, University of California, Irvine. More information about the project, along with binary and source downloads, are available on the SourceForge project page.

From the release message:

Version 5.2.7 contains updates to quantization metadata, enhanced grid area diagnostics for check_map, and bug-fixes for ncclimo and ncremap.

New Features

1. Version 5.2.7 implements the final (we think) CF quantization metadata convention. The main change is that the keywords and container variable are now "quantization" instead of "lossy_compression".

   ncks -7 -v ps,ts --qnt_alg=btr --qnt default=9 --qnt ps=13 --cmp='shf|zst' in.nc out.nc
   ncks -m -C -v ps,ts,quantization_info out.nc
   netcdf out {
   ...
   float ps(time,lat,lon) ;
   ps:standard_name = "surface_air_pressure" ;
   ps:units = "Pa" ;
   ps:quantization = "quantization_info" ;
   ps:quantization_nsb = 13 ;
   ps:quantization_maximum_relative_error = 6.103516e-05f ;
   
   char quantization_info ;
   quantization_info:algorithm = "bitround" ;
   quantization_info:implementation = "NCO version 5.2.7" ;
   
   float ts(time) ;
   ts:standard_name = "surface_temperature" ;
   ts:units = "K" ;
   ts:quantization = "quantization_info" ;
   ts:quantization_nsb = 9 ;
   ts:quantization_maximum_relative_error = 0.0009765625f ;
   } // group /
   

   http://nco.sf.net/nco.html#qnt_alg
   http://nco.sf.net/nco.html#qnt
2. ncks --chk_map now produces additional diagnostics about the source and destination grids. Then new diagnostics are values and locations (index, latitude, longitude) of the minimum and maximum gridcell areas (usually in sterradians), together with the effective quadrilateral size on Earth of the gridcell (assuming a square shaped cell of equivalent area):

   ncks --chk_map map_ne30pg2_to_cmip6_180x360_nco.20200901.nc
   ...
   area_a min, ~dx: 4.9093515660647374e-04 sr, 141.14 km in grid A cell
   [21544,+45.7267,+177.69]
   area_a max, ~dx: 6.8523331840188574e-04 sr, 166.75 km in grid A cell
   [9061,+0.749936,+180.75]
   ...
   area_b min, ~dx: 2.6580860638549120e-06 sr, 10.39 km in grid A cell
   [60,-42.7476,+359.25]
   area_b max, ~dx: 3.0460968486221404e-04 sr, 111.18 km in grid A cell
   [32272,-68.5,+135.5]
   

   These diagnostics can be useful in identifying grid-related dynamics issues, e.g., due to CFL conditions.
   http://nco.sf.net/nco.html#chk_map

Additional details are available in the ChangeLog.