CF Standard Names
This document summarizes selected CF standard names used in the AC1 dataset for describing seawater properties and meridional transports.
Coordinates
latitude
Canonical Units: degree_north
Description: Latitude is positive northward. In rotated grids, use grid_latitude instead.
longitude
Canonical Units: degree_east
Description: Longitude is positive eastward. In rotated grids, use grid_longitude instead.
Temperature
sea_water_conservative_temperature
Canonical Units: K
Description: Conservative Temperature is defined as part of the Thermodynamic Equation of Seawater 2010 (TEOS-10), adopted in 2010 by the International Oceanographic Commission (IOC). It is specific potential enthalpy (see sea_water_specific_potential_enthalpy) divided by a fixed value of the specific heat capacity of sea water:
Conservative Temperature is a significantly more accurate measure of seawater heat content than potential temperature (θ), improving precision by a factor of ~100. It is proportional to the heat content per unit mass of seawater.
References: - TEOS-10: https://www.teos-10.org - McDougall, 2003: doi:10.1175/1520-0485(2003)033<0945:PEACOV>2.0.CO;2
Metadata Guidance: Strongly recommended to include a units_metadata attribute: “on-scale” or “difference”.
sea_water_temperature
Canonical Units: K
Description: Sea water temperature refers to the in situ temperature of seawater. Use a vertical coordinate to specify measurement depth.
Historical Context: - IPTS-48 (1948–1967) - IPTS-68 (1968–1989) - ITS-90 (1990 onward)
Conversion Equations:
Metadata Guidance: Use units_metadata: “on-scale” or “difference”.
Salinity
sea_water_absolute_salinity
Canonical Units: g kg⁻¹
Description: Absolute Salinity ( S_A ), from TEOS-10, is the mass fraction of dissolved material in seawater. It accounts for regional composition variations and yields accurate density calculations.
Metadata Guidance: Include a comment attribute specifying the TEOS-10 software version and anomaly climatology.
References: - TEOS-10: https://www.teos-10.org - Millero et al., 2008: doi:10.1016/j.dsr.2007.10.001
sea_water_practical_salinity
Canonical Units: 1 (dimensionless)
Description: Practical Salinity ( S_P ) is computed from conductivity and is reported on the Practical Salinity Scale of 1978 (PSS-78). Use only for post-1978 data derived from conductivity.
References: - TEOS-10: https://www.teos-10.org - Lewis, 1980: doi:10.1109/JOE.1980.1145448
sea_water_salinity
Canonical Units: 1e-3 (dimensionless; parts per thousand)
Description: Generic term for salt content in seawater. Use only when the salinity does not conform to a defined standard. Deprecated for post-1978 observations in favor of sea_water_practical_salinity.
Conversion Notes:
Pressure
sea_water_pressure
Canonical Units: dbar
Description: Sea water pressure includes the pressure from the overlying seawater, sea ice, atmosphere, and other media. Use sea_water_pressure_due_to_sea_water to isolate seawater-only pressure.
sea_water_pressure_at_sea_floor
Canonical Units: dbar
Description: Pressure at the ocean bottom, including contributions from all overlying media.
reference_pressure
Canonical Units: Pa
Description: A constant scalar value representing reference pressure (e.g., for calculating potential density).
Density
sea_water_sigma_theta
Canonical Units: kg m⁻³
Description: Sigma-theta of sea water is the potential density (i.e. the density when moved adiabatically to a reference pressure) minus 1000 kg m⁻³. To specify the reference pressure, include a scalar coordinate variable with standard name reference_pressure. Not to be confused with ocean_sigma_coordinate.
ocean_sigma_z_coordinate
Canonical Units: 1 (dimensionless)
Description: A parametric vertical coordinate. See Appendix D of the CF convention for details.
ocean_sigma_coordinate
Canonical Units: 1 (dimensionless)
Description: A parametric vertical coordinate used in ocean models. Not to be confused with sea_water_sigma_theta.
sea_water_potential_density
Canonical Units: kg m⁻³
Description: The density a parcel of sea water would have if moved adiabatically to a reference pressure (typically sea level). Use reference_pressure as a scalar coordinate. Subtracting 1000 kg m⁻³ yields sea_water_sigma_theta.
sea_water_neutral_density
Canonical Units: kg m⁻³
Description: Neutral density is a variable that approximates the local slope of the neutral tangent plane. Differences between neutral density and potential density anomaly can be substantial away from the equator. See Jackett & McDougall (1997) for details.
Velocity
baroclinic_northward_sea_water_velocity
Canonical Units: m s⁻¹
Description: Northward component of baroclinic sea water velocity.
barotropic_northward_sea_water_velocity
Canonical Units: m s⁻¹
Description: Northward component of barotropic sea water velocity.
Transport
northward_ocean_freshwater_transport
Canonical Units: kg s⁻¹
Description: Northward component of total ocean freshwater transport, including both seawater and sea ice.
northward_ocean_freshwater_transport_due_to_gyre
Canonical Units: kg s⁻¹
Description: Part of northward freshwater transport due to ocean gyre circulation, calculated from deviations from zonal means. Excludes parameterized eddy velocity.
northward_ocean_freshwater_transport_due_to_overturning
Canonical Units: kg s⁻¹
Description: Part of northward freshwater transport due to overturning circulation, based on zonal means. Excludes parameterized eddy velocity.
northward_ocean_heat_transport
Canonical Units: W
Description: Northward component of total ocean heat transport, including seawater and sea ice.
northward_ocean_heat_transport_due_to_gyre
Canonical Units: W
Description: Part of northward heat transport due to ocean gyre circulation, using deviations from zonal means. Excludes parameterized eddy velocity.
northward_ocean_heat_transport_due_to_overturning
Canonical Units: W
Description: Part of northward heat transport due to overturning circulation, based on zonal means. Excludes parameterized eddy velocity.
ocean_volume_transport_across_line
Canonical Units: m³ s⁻¹
Description: Transport across a specified line (e.g., latitude), defined as the line integral of normal volume transport across that section.
streamfunction
ocean_meridional_overturning_mass_streamfunction
Canonical Units: kg s⁻¹
Description: Overturning streamfunction including all resolved and parameterized processes that impact mass or volume transport.
ocean_meridional_overturning_streamfunction
Canonical Units: m³ s⁻¹
Description: Overturning streamfunction excluding the parameterized eddy velocity.