Underway pH
Discrete pH and BGC-SUMO pH data were converted from pH values measured at the BGC-SUMO TSG temperature to in situ pH values using the ship-board TSG intake temperature. This pH temperature conversion calculation was performed using the program CO2SYSv3 (Lewis & Wallace, 1998; Sharp et al., 2020; van Heuven et al., 2011). An average of discrete TA samples (QF as good), also collected during these cruises, was used in the CO2SYSv3 calculations. The following constants were chosen for CO2SYSv3 input: K₁K₂ of Lueker et al (2000); K_SO4 of Dickson (1990); KF of Perez & Fraga (1987); TB of Lee (2010). The mean of pH residuals (BGC-SUMO pH – discrete pH, both at BGC-SUMO TSG temperature) was near zero for all cruises (4.5x10^-07, -1.0x10^-06, -3.3x10^-06; for cruises 2019-006, 2019-008, 2020-001, respectively).

Problem report
Underway pH measurements during the sensor warm-up phase for each cruise were given a Quality Flag (QF) of 4 or 3, determined based on comparison with in-line temperature and salinity data. During the return transits for cruises 2019-006 and 2020-001, large discrepancies between BGC-SUMO and discrete pH data were observed. These underway pH data were assigned a QF = 3. Unrealistic pH data for this region (values > 8.4 and < 7.6) were also assigned a QF of 4. A moving mean filter with a sliding window of 200 (~2 second resolution) was applied to the pH data to identify irregular spikes, which were assigned a QF = 3. When ship TSG temperature or salinity values were missing, BGC-SUMO pH data were set to NaN.

=================
BCO-DMO Processing:

Imported data from source file "combined_SUMO_data_FORMATTED.xlsx" into the BCO-DMO data system.
Data file imported using missing data identifiers "NaN”. The missing data identifier "NaN" in the original source file will be displayed as appropriate based on the type of file you download from the BCO-DMO data system. For example, missing data will be shown as blank (null) values in the csv files. In MATLAB .mat files it will be displayed as NaN. When viewing data at BCO-DMO the missing value will be shown as "nd" meaning "no data."
Converted separate date and time fields to single datetime column with ISO8601 format.
Added column for vessel/ship
Added conventional header with dataset name, PI name, version date.
Modified parameter (column) names to conform with BCO-DMO naming conventions. (The only allowed characters are A-Z,a-z,0-9, and underscores. No spaces, hyphens, commas, parentheses, or Greek letters).

underway_ph.csv