Processing Steps |
- Parameter or Variable: pCO2 (fCO2) autonomous; Abbreviation: fCO2W@SST; Unit: uatm; Observation type: Surface underway; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Measured; Sampling instrument: Seawater pump; Location of seawater intake: Bow; Analyzing instrument: Neill 1st generation (G1); precursor to General Oceanics GO 8050 systems; Detailed sampling and analyzing information: The sampling and analyzing methods of the Neill/General Oceanics Underway pCO2 systems are described in detail in: Pierrot, D.; Neill, C.; Sullivan, K.; Castle, R.; Wanninkhof, R.; Lüger, H.; Johannessen, T.; Olsen, A.; Feely, R.A.; and Cosca, C.E. (2009). Recommendations for autonomous underway pCO2 measuring systems and data-reduction routines. Deep-Sea Res., II, v. 56, pp. 512-522.; Equilibrator type: Shower head; Equilibrator volume: ~0.5 L; Is the equilibrator vented or not: Vented; Water flow rate: 1.5 to 2 L/min; Gas flow rate: ~0.8 L/m; How was temperature inside the equilibrator measured: Hart Scientific model 1521 digital thermometer, serial number A77488, with an NIST traceable model 5610 thermistor probe, serial number A9B0916. Accurate to ± 0.01°C.; How was pressure inside the equilibrator measured: Setra 239 differential pressure transducer, accurate to ± 0.15 hPa. The equilibrator was passively vented to a secondary equilibrator, and the Licor sample output was vented to the laboratory when CO2 measurements were made, thus equilibrator headspace pressure was assumed to be laboratory pressure. Pressure in the laboratory was measured with a GE Druck barometer with an accuracy of ± 0.01 %fs.; Drying method for gas: From Pierrot, et al.: Sample air is dried in a condenser that is cooled to 4-5 oC by a Peltier thermoelectric device. This partially dried air flushes a chamber that is vented and remains at ambient pressure. The dried air inside the chamber is used as the counter flow in the Nafion® tubing. A vacuum pump pulls the dried air from the chamber first through a fixed restrictor and then through the Nafion® tubes, thus creating an absolute pressure and corresponding partial pressure gradient for water vapor across the membrane. When atmospheric air is measured, some of the partially dried air (80-100 ml/min) is pushed through a v tube, the analyzer and out a vent instead of flushing the chamber. The headspace gas, when being measured, is circulated in a closed loop through the analyzer at a rate similar to that of the atmospheric air (80-100 ml/min). It is dried first in the condenser, then in a Nafion® tube prior to entering the analyzer and being returned to the equilibrator. Typically, the water mole fraction (xH2O) in the dried gas is about 2 parts per thousand (ppt), which corresponds to a dew point temperature of about -20 °C. The liquid water condensed out of the sample air streams is removed by peristaltic pumps into the vent equilibrator at intervals determined by the user.; SEA CO2 gas detector manufacturer: Licor, Inc; SEA CO2 gas detector model: Licor 6262, IRG3-1242; SEA CO2 gas detector resolution: 0.2 µatm; SEA CO2 gas detector uncertainty: 0.3 µatm for equilibrator measurements, 0.2 µatm for atmospheric measurements; Standardization technique: The system runs a full cycle in approximately 112 minutes. The cycle starts with 4 standard gases, then measures 10 atmospheric samples followed by 60 surface water samples. Each new gas is flushed through the Licor Analyzer for 4 minutes prior to a 10 second reading from the analyzer during which the sample cell is open to the atmosphere. Subsequent samples of the same gas are flushed through the Licor Analyzer for 30 seconds prior to a stop-flow measurement.; Standardization frequency: Every 112 minutes; Standard gas manufacturer: Standard gases are supplied by NOAAs Earth System Research Laboratory, Global Monitoring Division, in Boulder, CO, and are directly traceable to the WMO scale.; Standard gas concentration: LL55868, 296.35 ppm; LL55864, 355.07 ppm; LL55867, 397.48 ppm; LL55866, 468.48 ppm; Standard gas uncertainty: 0.01 ppm; Water vapor correction method: Details of the data reduction are described in Pierrot, et.al. (2009).; Temperature correction method: Details of the data reduction are described in Pierrot, et.al. (2009).; At what temperature was pCO2 reported: In situ sea surface temperature; Uncertainty: ± 2 µatm; Quality flag convention: WOCE quality control flags are used: 2 = good value, 3 = questionable value, 4 = bad value; Method reference: Pierrot, D., Neill, C., Sullivan, K., Castle, R., Wanninkhof, R., Lüger, H., Johannessen, T., Olsen, A., Feely, R. A., & Cosca, C. E. (2009). Recommendations for autonomous underway pCO2 measuring systems and data-reduction routines. Deep Sea Research Part II: Topical Studies in Oceanography, 56(8-10), 512-522. https://doi.org/10.1016/j.dsr2.2008.12.005; Researcher name: Catherine E. Cosca; Researcher institution: Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration.
- Parameter or Variable: Sea Surface Temperature; Abbreviation: SST(TSG)_C; Unit: Degree Celcius; Observation type: Surface Underway; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Measured; Sampling instrument: Seabird 38, serial number 3848581-0383; Uncertainty: 0.0025°C.
- Parameter or Variable: Salinity; Abbreviation: SAL(TSG)_PERMIL; Unit: permil; Observation type: Surface Underway; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Measured; Sampling instrument: Seabird 45, serial number 4539646-0143; Uncertainty: 0.005 PSU.
- Parameter or Variable: Mole fraction of CO2 in the equilibrator headspace (dry) at equilibrator temperature; Abbreviation: xCO2W_ppm; Unit: ppm; Observation type: Surface Underway; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Measured; Sampling instrument: Licor 6262, IRG3-1242; Analyzing instrument:; Duration:; Detailed sampling and analyzing information: See Pierrot et al. for details.; Uncertainty: 0.3 ppm.
- Parameter or Variable: Mole fraction of CO2 measured in dry outside air; Abbreviation: xCO2A_ppm; Unit: ppm; Observation type: Surface Underway; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Measured; Sampling instrument: Licor 6262, IRG3-1242; Analyzing instrument:; Duration:; Detailed sampling and analyzing information: See Pierrot et al. for details.; Uncertainty: 0.2 ppm.
- Parameter or Variable: Mole fraction of CO2 measured in dry outside air associated with each water analysis.; Abbreviation: xCO2A_interpolated_ppm; Unit: ppm; Observation type: Surface Underway; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Measured; Calculation method and parameters: Values are interpolated between measurements of xCO2A_ppm; Sampling instrument: Licor 6262, IRG3-1242; Analyzing instrument:; Duration:; Detailed sampling and analyzing information: See Pierrot et al. for details.; Uncertainty: 0.2 ppm.
- Parameter or Variable: Partial pressure and fugacity of CO2 in air corresponding to the interpolated xCO2 (xCO2A_interpolated_ppm) at SST and 100% humidity; Abbreviation: pCO2A_uatm, fCO2A_uatm; Unit: µatm; Observation type: Surface Underway; In-situ / Manipulation / Response variable: In-situ observation; Measured or calculated: Measured; Calculation method and parameters: Values are interpolated between measurements of xCO2_ATM_ppm; Sampling instrument: Licor 6262, IRG3-1242; Analyzing instrument:; Duration:; Detailed sampling and analyzing information: See Pierrot et al. for details.; Uncertainty: 0.2 �atm .
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