Units

This document summarizes unit definitions for AMOCatlas Format v0.1 (A0.1), based on udunits2-base.xml with AMOC-specific extensions.

AMOCatlas Preferred Units

The following table summarizes the preferred units for common AMOC variables:

AMOCatlas Preferred Units
Variable Type	AC1.0 Unit	Rationale
Ocean volume transport	Sverdrup	Avoids Sv/sievert confusion
Heat transport	PW	Appropriate scale for oceanic heat transport
Temperature	degree_C	CF-compliant
Salinity	PSU, g kg-1	Uppercase standard
Density, potential density	kg m-3	Standard density unit
Velocity	m s-1	Standard velocity unit, positive north or east
Transport per unit depth	Sverdrup/m	Consistent with transport units
Pressure	dbar	Standard oceanographic pressure unit
Latitude	degree_north	CF-compliant, positive north
Longitude	degree_east	CF-compliant, positive east
Time	datetime64[ns]	Standard time representation in xarray and pandas
Depth	m	Depth below sea surface, positive downwards

AMOCatlas Unit Conversions
Original Unit	Canonical Unit	Factor	Notes
`cm/s`, `cm s-1`	`m s-1`	0.01	Velocity conversions
`S/m`	`mS cm-1`	0.1	Conductivity conversions
`Pa`, `kPa`	`dbar`	1/10000, 1/10	Pressure conversions
`Celsius`, `°C`	`degree_C`	1	Temperature unit normalization
`deg N`, `deg E`	`degrees_north`, `degrees_east`	1	Geographic coordinates (CF-compliant)
`psu`, `PSU`	1	1	Practical salinity unit (unitless)
`W`, `TW`, `MW`	`PW`	1e-15, 1e-3, 1e-9	Heat transport scaling to petawatts
`meters`, `m`	`m`	1
`kg/m3`	`kg m-3`	1	Density conversions
`1e6 m3/s`	`Sverdrup`	1/1e6	Ocean volume transport (no abbreviation)
`W`, `J`	`watt`, `joule`	base units	Energy and power base units

Note: Full “Sverdrup” spelling used to avoid confusion with “Sv” (sievert).

Standard prefixes supported by UDUNITS-2 for scaling base and derived units.

Notes: