The underway fCO2 data files consist of 15 columns of data:

JD               = Julian decimal day
Date             = month/day/year
Time             = 01:00:00 to 23:59:59
Lat              = Latitude (negative numbers for the southern hemisphere)
Long             = Longitude (negative numbers for the western hemisphere)
xCO2,w           = mole fraction of carbon dioxide in water (ppm)
xCO2,a           = mole fraction of carbon dioxide in air (ppm)
Eq Temp          = temperature recorded inside the equilibrator
Pressure         = atmospheric pressure (mB)
SST (TSG)        = sea surface temperature (°C) at the bow intake
Sal (TSG)        = salinity at the bow intake
f(CO2)w, equi    = fugacity of CO2 in the equilibrator (ľatm)
f(CO2)w, in situ = fugacity of CO2 in surface seawater (ľatm)
f(CO2)a          = fugacity of CO2 in air (ľatm)
delta fCO2       = f(CO2)w, in situ minus f(CO2)a (ľatm)