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".