types:
  byte enum cloud_t {
     Clear = 0, Cumulonimbus = 1, Stratus = 2, 
     Stratocumulus = 3, Cumulus = 4, Altostratus = 5, 
     Nimbostratus = 6, Altocumulus = 7, Missing = 127
     };
dimensions:
     time = unlimited;
variables:
     cloud_t primary_cloud(time);
        cloud_t primary_cloud:_FillValue = Missing;
data:
     primary_cloud = Clear, Stratus, Cumulus, Missing, ...;

Potential uses for enumerations

• Alternative for using strings with flag_values and flag_meanings attributes for quantities such as soil type, cloud type, ...
• Improving self-description while keeping data compact

2007 Unidata NetCDF Workshop for Developers and Data Providers > Introduction to NetCDF-4