M/S Silja Serenade (Helsinki-Stockholm) pCO2 underway measurements in 2018-05

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 boundary91111111 => CO2_ppm_wet => 20 ppm to 2000 ppm19111111 => T equ => -1 °C to 30 °C11911111 => T tech => -1 °C to 30 °C11191111 => Salinity => 5 to 811119111 => Pressure => 0.9 to 1.111111911 => coeff_A/coeff_B/coeff_C => -50/0.9/-0.0001 to 100/1.3/0.000111111191 => SHEQ_flow_LPM/LICOR_flow => 1.0/50 to N/A/N/A11111119 => 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)^2Polynomial 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 equilibratortemperature, 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).

质量控制：已剔除校准、清洁、维护及低流量排放阶段获取的测量数据。
标记系统：本数据集采用标记系统开展质量控制。通过标记质控的合格数据，标记为11111111。若原始CO₂分压（未经过校准校正）超出范围（20~1200 ppm），则标记的首位数字变为9；若仅存在该异常情况，则标记为9111111。所有标记及其阈值范围如下表所示：
91111111 → 湿相CO₂摩尔分数（CO2_ppm_wet）→ 20 ppm ~ 2000 ppm
19111111 → 平衡温度（T_equ）→ -1 ℃ ~ 30 ℃
11911111 → 技术温度（T_tech）→ -1 ℃ ~ 30 ℃
11191111 → 盐度 → 5 ~ 8
11119111 → 压力 → 0.9 ~ 1.1
111111911 → 系数A/系数B/系数C（coeff_A/coeff_B/coeff_C）→ -50/0.9/-0.0001 ~ 100/1.3/0.0001
111111191 → SHEQ流量/LI-COR流量（SHEQ_flow_LPM/LICOR_flow）→ 1.0/50 ~ 未限定/未限定
11111119 → 人工目视判定的不合格数据
数据计算：LI-840A观测得到的CO₂摩尔分数记为湿相CO₂摩尔分数（CO2_ppm_wet）。
干空气基准下的CO₂摩尔分数按如下公式计算：
CO2_ppm_dry = CO2_ppm_wet / (1 - H2O_ppt/1000)
其中H2O_ppt为LI-840A测得的H₂O摩尔分数。
每4小时执行一次校准序列，基于观测值与真实摩尔分数拟合得到二阶多项式函数：
CO2_ppm_dry_cal_cor = coeff_A + coeff_B * CO2_ppm_dry + coeff_C * (CO2_ppm_dry)^2
多项式系数（coeff_A、coeff_B与coeff_C）在校准周期之间通过插值得到。
干空气中的CO₂分压按如下公式计算：
pCO2_uatm_dry = CO2_ppm_dry_cal_cor * P_eq_atm
湿空气中的CO₂分压参考Dickson与Goyet（1994）的方法计算：
pCO2_uatm = pCO2_uatm_dry * (1 - Pws_eq_atm)
其中饱和水汽压Pws_eq_atm由平衡温度（T_eq_degC）计算得到（Wagner与PruB，2002，公式2.5）。
针对进气口的温度校正CO₂分压计算如下：
pCO2_uatm_temp_corr = pCO2_uatm * exp[ A * (T_in_degC - T_eq_degC) ]
其中A=0.0423（Takahashi等，1993）。