CalCOFI's Seabird 911+ CTD includes dual Temperature, Conductivity, and Oxygen sensor arrays (dual O2s since Jul 2009) that are separately plumbed & pumped. Data from these sensors are labeled Temp1, Salt1, Ox1, & Temp2, Salt2, Ox2 respectively (refer to the index below for units). The "FinalQC" version of the CTD csvs also include oxygens in umol/kg (Ox1uM, Ox2uM) and data-quality code columns. Data codes (flags) are used to identify bad (datacode "9") or questionable (datacode "8") data.

CalCOFI collects seawater samples using 24-10L metal-free bottles mounted on an epoxy-coated rosette. The seawater samples are analyzed & processed at-sea then undergo a series of additional post-cruise calibration, data-processing & data-quality steps on shore. Initial merging & comparison of CTD & bottle data generates the "prelim" CTD csvs used for point-checking. Once bottle data have been gone through CalCOFI's data quality control protocols, the final bottle data are merged with 1m-binavg CTD sensor data from the same cast and depths. CTD salinities deeper than 350m are subtracted from matching bottle (depth) salinities. These differences are averaged into offsets for both primary and secondary CTD salinities and applied to all CTD salinities. Bottle-corrected CTD salinities are reported as Salt1_Corr (primary), Salt2_Corr (secondary), and SaltAve_Corr (ave of both).

Oxygen bottle samples are plotted versus the corresponding CTD primary (Ox1) and secondary (Ox2) oxygen sensor data. Regression coefficients to correct CTD oxygens are derived for both sensors in ml/L and µM/kg - 4 plots total. The bottle-corrected CTD sensor data are reported in the Ox1_CruiseCorr (ml/L) and Ox1µM_CruiseCorr (µM/Kg) and Ox2_CruiseCorr and Ox2_µM_CruiseCorr data columns.

One-meter binavg CTD fluorometer voltages are plotted versus the corresponding depth chlorophyll bottle samples to derive regression coefficients. These are applied to the 1m binavg fluorometer voltages from 0-200 meters, estimating chlorophyll-a  & reported as EstChl_CruiseCorr.

A plot of 1m binavg ISUS voltages versus nitrate (NO3) using all the nitrate bottle samples generates regression coefficients. These are applied to the 1m binavg ISUS voltage to derive estimated nitrate data, reported as EstNO3_CruiseCorr
Note: when bottle data are plotted versus CTD sensor data, bottle data "fliers" are excluded so they do not influence the bottle data sensor correction coefficients.

In addition to cruise-corrected CTD data, there are station-corrected data. These data are bottle-corrected CTD data that use the bottle data from only the matching station. These data are generated using CalCOFI-developed software that dynamically calculates the correction coefficients and applies them automatically to CTD sensor data. These data are usually the best data since this method adjusts for station-to-station variablilty in the sensor behavior such as sensor drift. These data are reported as "StaCorr": Ox1_StaCorr, Ox2_StaCorr, EstChl_StaCorr, EstNO2_StaCorr. The coefficients applied dynamically for each station may be different and are tabulated in each cruises CTD metadata file "DBcoeff.csv".

Please note that the FinalQC format with additional data quality code columns was adopted in 2015. CTD data files with the 82-column format are labeled "FinalQC". Cruise files labeled "Final" are being reprocessed to add the data-quality columns, data codes, & O2s in uM/Kg. When updated, they will be relabled "FinalQC".  Note that most data values, particularly T & S, should remain unchanged - only the format is changing and data-flags added.
QCodes: blank or "0" code = good data; "8" = questionable data; "9" = bad data