 
  
   
    
 
 
age_of_sea_ice" to "zenith_angle". 
standard_name variable attribute.standard_name attribute identifies
  the physical quantity of a variable, for example "air_temperature",
  "divergence_of_wind", "plant_respiration_carbon_flux", or
  "tendency_of_atmosphere_mass_content_of_particulate_organic_matter_dry_aerosol_due_to_net_production_and_emission".
   
  units attribute, e.g. "kg m-2 s-1".