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Laakso, Lauri; Kielosto, Sami; Honkanen, Martti (2021): M/S Silja Serenade (Helsinki-Stockholm) pCO2 underway measurements in 2018-04 [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.927993, In: Laakso, L et al.: M/S Silja Serenade (Helsinki-Stockholm) pCO2 data 2018-2020 [dataset publication series]. PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.928025 (dataset in review)

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Funding:
Bundesministerium für Bildung und Forschung, Bonn (BMBF), grant/award no. 03F0773A: Integrated carbon and trace gas monitoring for the Baltic Sea
Coverage:
Median Latitude: 59.749615 * Median Longitude: 19.821305 * South-bound Latitude: 59.593470 * West-bound Longitude: 18.803380 * North-bound Latitude: 59.995890 * East-bound Longitude: 21.026990
Date/Time Start: 2018-04-12T17:51:00 * Date/Time End: 2018-04-12T23:37:00
Event(s):
Serenade_2018-04 * Latitude Start: 60.166000 * Longitude Start: 24.933000 * Latitude End: 59.325000 * Longitude End: 18.050000 * Date/Time Start: 2018-04-01T00:00:00 * Date/Time End: 2018-04-30T00:00:00 * Campaign: Silja-Serenade_cruises * Basis: Silja Serenade * Method/Device: Underway cruise track measurements (CT) * Comment: Helsinki-Mariehamm-Stockholm
Comment:
Quality control:
Measurements during calibration, cleaning, maintenance and low discharge have been removed.
-----
Flag system:
A flag system is applied to the data. Good data that passes the flag control, gets the flag of 11111111. If the raw CO2 partial pressure (not calibration corrected) is out of boundaries (20-1200 ppm), the first digit changes to 9, i.e. if this is only abnormality, the flag would be 9111111. All flags and their boundary limits are listed in the table below.
--
Flag => Parameter => Lower boundary to Upper boundary
91111111 => CO2_ppm_wet => 20 ppm to 2000 ppm
19111111 => T equ => -1 °C to 30 °C
11911111 => T tech => -1 °C to 30 °C
11191111 => Salinity => 5 to 8
11119111 => Pressure => 0.9 to 1.1
11111911 => coeff_A/coeff_B/coeff_C => -50/0.9/-0.0001 to 100/1.3/0.0001
11111191 => SHEQ_flow_LPM/LICOR_flow => 1.0/50 to N/A/N/A
11111119 => Visually inspected bad data
-----
Calculations:
The CO2 molar fraction observed by the LI-840A is denoted as wet CO2 molar fraction (CO2_ppm_wet).
--
The molar fraction with respect to dry air is calculated as,
CO2_ppm_dry = CO2_ppm_wet / (1 - H2O_ppt/1000),
where H2O_ppt is the H2O molar fraction measured by the LI-840A.
--
For each calibration sequence every 4 hour, a 2nd order polynomial function is fitted to the observed and real molar fractions:
CO2_ppm_dry_cal_cor = coeff_A + coeff_B * CO2_ppm_dry + coeff_C * (CO2_ppm_dry)^2
Polynomial coefficients (coeff_A, coeff_B and coeff_C) are interpolated between the calibrations.
--
CO2 partial pressure in dry air is calculated as,
pCO2_uatm_dry = CO2_ppm_dry_cal_cor * P_eq_atm
--
The CO2 partial pressure in wet air (Dickson and Goyet, 1994),
pCO2_uatm = pCO2_uatm_dry * (1 - Pws_eq_atm)
where saturation water vapor pressure, Pws_eq_atm, is calculated from equilibrator
temperature, T_eq_degC (Wagner and PruB, 2002, Eq. 2.5).
--
Temperature corrected CO2 partial pressure is given for the inlet,
pCO2_uatm_temp_corr = pCO2_uatm * exp [ A* (T_in_degC - T_eq_degC)]
where A = 0.0423 (Takahashi et al., 1993).
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1DATE/TIMEDate/TimeLaakso, LauriGeocode – UTC
2LATITUDELatitudeLaakso, LauriGeocode
3LONGITUDELongitudeLaakso, LauriGeocode
4xCO2 (water) at sea surface temperature (wet air)xCO2water_SST_wetµmol/molLaakso, Lauriread from LI-840A
5xCO2 (water) at sea surface temperature (dry air)xCO2water_SST_dryµmol/molLaakso, Lauri
6Temperature at equilibrationTequ°CLaakso, LauriDigital oceanographic thermometer, Sea-Bird, SBE 38
7Temperature, technicalT tech°CLaakso, Lauriinlet temperature
8Temperature, differencedelta T°CLaakso, Lauri
9Water vapour mixing ratioH2O mix ratiommol/molLaakso, Lauri
10PressurePressatmLaakso, Laurisaturation H2O pressure inside the chamber (calculated)
11PressurePressatmLaakso, LauriTotal pressure inside the equilibrium chamber
12Quality flagQFLaakso, Laurifor CO2, see dataset comment for details
13SalinitySalLaakso, LauriThermosalinograph, Sea-Bird, SBE 45PSU
14Flow rateFlow ratel/minLaakso, LauriSHEQ, water flow rate to the showerhead equilibrators
15Flow rateFlow ratel/minLaakso, LauriLICOR, air flow rate to the gas analyser ml/min recalc!
16Flow rateFlow ratel/minLaakso, Lauritotal water flow rate
Size:
6187 data points

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