UNDERWAY pCO₂ DATA FILE FORMAT

(Focuses on results from underway measurement systems.)

I. REQUIRED ELEMENTS

Measured atmospheric information

• Date / Time of Measurement (UTC)
• Position of measurement
  • Latitude in decimal degrees (North is positive, South is negative)
  • Longitude in decimal degrees (East is positive, West is negative)
• Mole fraction of CO₂ in ambient atmosphere (µmol/mol in dry air)
• Atmospheric pressure at sea-surface pressure (hPa)

Measured seawater information

• Date / Time of Measurement (UTC)
• Position of measurement
  • Latitude in decimal degrees (North is positive, South is negative)
  • Longitude in decimal degrees (East is positive, West is negative)
• Mole fraction of CO₂ in air from equilibrator (µmol/mol)
• Mole fraction of of H₂O in air from equilibrator (µmol/mol)
• Pressure of equilibration = the pressure in the equilibration vessel (hPa)
• Temperature of equilibration = the temperature of the seawater in equilibrator at the time of equilibration (°C)
• Sea surface temperature (in situ) (°C)
• Sea surface salinity (in situ)

II. DERIVED PARAMETERS

Atmosphere

• x(CO₂) value for the ambient atmosphere (µmol/mol in dry air); interpolated to match the date/time/position of the seawater information in this section

Seawater

• f(CO₂) for air in equilibrium with seawater at sea surface temperature (µatm). Note: the air will be at 100% humidity
• p(CO₂) for air in equilibrium with seawater at sea surface temperature (µatm). Note: the air will be at 100% humidity
• x(CO₂) for air in equilibrium with the seawater at sea surface temperature and 1013.25 hPa applied pressure (expressed as µmol/mol in dry air)

III. OPTIONAL ANCILLARY INFORMATION

• Quality flags
• Detailed Ships Heading Information
• Other measurements (chemical, physical, meteorological)