Measurements of pH (on total scale) and other variables collected from surface undewray observations using Durafet pH electrode and Chloride Ion Selective Electrode and other instruments from NOAA Ship R/V Ronald H. Brown in the North Atlantic Ocean and South Atnaltic Ocean from during the CLIVAR/G

An automated underway pH system was operated in the hydro lab of the R/V Ronald H. Brown during the CLIVAR/GO-SHIP Repeat Section A13.5 cruise in 2010. pH was measured every 30 seconds using a Durafet III pH combination electrode and an Orion Chloride Ion Selective Electrode (Cl-ISE). This combination allows for the calculation of pH using two reference electrodes: the internal reference electrode of the Durafet (pHint) and the Cl-ISE directly submersed in seawater (pHext). pH is reported on 30 second intervals to provide the maximum flexibility for assessing precision and capturing small scale features in the ocean. Seawater continually flowed through a flowcell that housed the Durafet and Cl-ISE, then a SBE45 Micro Thermosalinograph. The temperature inside the flowcell was assumed to be the same as the SBE45. The salinity measurements from the SBE45 were not reliable on this cruise (based on comparisons with discrete bottle samples), therefore salinity from the SBE45 located next to the underway fCO2 system [Wanninkhof, 2012] was interpolated onto the pH time stamp. Latitude, longitude, and sea surface temperature (SST) were also interpolated from the underway fCO2 data set. All pH is reported on the total scale, and at SST. All data reported here are considered good. We recommend the use of pHext, as we believe this is more accurate than pHint.

2010年CLIVAR/GO-SHIP重复断面A13.5航次期间，自动化走航pH监测系统在“罗纳德·H·布朗”号（R/V Ronald H. Brown）科研调查船的水文实验室中投入运行。本系统采用Durafet III型pH复合电极（Durafet III pH combination electrode）与奥利安氯离子选择性电极（Orion Chloride Ion Selective Electrode, Cl-ISE），每30秒完成一次pH测量。该电极组合可借助两支参比电极实现pH值计算：其一为Durafet内置参比电极（pHint），其二为直接浸没于海水中的Cl-ISE（pHext）。为最大化兼顾监测精度评估与海洋中小尺度水文特征捕捉的灵活性，本数据集以30秒间隔输出pH测量结果。海水持续流经搭载Durafet与Cl-ISE的流通池，随后流经SBE45型微型温盐仪（SBE45 Micro Thermosalinograph）。默认流通池内水温与SBE45的测量水温一致。本次航次中SBE45的盐度测量结果不可靠（经与离散采水器样本对比验证），因此将紧邻走航式fCO₂（水中二氧化碳分压）系统的SBE45盐度数据[Wanninkhof, 2012]，插值匹配至pH测量的时间戳序列。纬度、经度与海表温度（Sea Surface Temperature, SST）数据同样从走航式fCO₂数据集中插值得到。所有pH测量结果均采用总标度（total scale）报告，且对应测量时的海表温度。本次报告的全部数据均经质控认定为有效。我们推荐优先使用pHext，因其相较于pHint具备更高的测量准确性。