Temperature and salinity (parameter names temp and sal): The CTD had dual CT sensors. For profiles where the two sensors agreed, a 51- (2.1 s) point median filter was applied to the mean of the two sensors. For profiles or regions of the profile where the two sensors disagreed, data from the sensor with the lesser variability was chosen and a 101-point (4.2 s) median filter was applied to only that sensor. Further manual smoothing was performed for a few casts. For more details on temperature and salinity processing, see Ship_TS_despiking-NAB08.pdf.
Dissolved oxygen, O2 (parameter name O2_cal): The sensor was calibrated immediately before the cruise. The factory calibration was applied to SBE43 oxygen sensor output and data were converted to µmol kg-1 and aligned with Winkler O2 measurements (included in KN193-03 bottle file). A time-dependent quadratic correction was applied to the SBE data, with resulting measurement error of 3.2 µmol kg-1. For more details, see Oxygen_Calibration-NAB08.pdf.
Particulate attenuation coefficient, cp (parameter name beam_cp): The factory calibration was used to convert C-Star s/n 1090 voltage to particulate attenuation coefficient, cp, m-1); the calibration factor did not change between pre-cruise and post-cruise factory calibration. C-Star s/n 284 was cross calibrated with C-Star s/n 1090 through a series of simultaneous ship/Biofloat48 calibration profiles. The final product contains cross-calibrated cp coefficients for all three C-Stars. Complete details of the transmissometer intercalibration procedure are in C-Star calibration report (C-Star_Calibration-NAB08.pdf).
Particulate organic carbon (POC) derived from cp (parameter name POC_cp): A linear regression was calculated to convert cp to POC using POC measurements from bottle samples (KN19303_bottle_file.mat). The cp values used in the regression were median cp values from a 30-s stationary period immediately before the bottle was fired; only data from C-Star s/n 1090 were used in the regression. These data are reported in the accompanying bottle file (KN19303_bottle.mat). The regression used to derive the POC product (poc_cp) from cp is:
POC (mg C m-3) = cp (m-1) * 408 (mg C m-2) – 10 (mg C m-3); r2 = 0.80,
This relationship is empirical and it should not be applied to the other cruises without independent verification. For more details, see POC_cp_bbp_Calibration-NAB08.pdf.
Particulate backscattering coefficient, bbp (parameter name bbp700): Backscattering voltage was converted to ? at 140° by subtracting dark voltages (median in-situ dark voltage, 0.078 V) and multiplying by factory calibration scale factors, modified based on measurements and calculations of Sullivan et al. (subm.). The calibration factor did not change between pre-cruise and post-cruise factory calibration. ? at 140° was converted to bbp (m-1) by subtracting ? of seawater (Zhang et al., 2009) and multiplying by 2?? (where ? = 1.132). See calibration report for more details: Backscatter_Calibration-NAB08.pdf.
Particulate organic carbon (POC) derived from bbp (parameter name POC_bbp): Ship-based bbp estimates over the entire experiment were ~20% higher on the CTD downcasts than the upcasts. This systematic difference may be due to the optical properties of aggregates (Briggs, 2010), but remains under investigation. Downcast data only are included for the CTD profiles (parameter name bbp700). Because of the systematic difference between bbp on the downcast vs. upcast and ~30-s stationary period, the relationship between stationary bbp and POC data in the bottle file cannot be directly applied to calculate downcast bbp to POC. Hence, the regression equation below was used to generate the POC product from downcast data: an 11-point (11 s) median filter was applied to the downcast bbp data, and bbp data were interpolated in density space to align downcast and upcast bbp. This data set was used to produce a regression for application to downcast bbp:
POC (mg C m-3) = bbp_downcast (m-1) * 35800 (mg C m-2) – 16.2 (mg C m-3); r2 = 0.81.
This relationship is empirical and it should not be applied to the other cruises without independent verification. For more details, see POC_cp_bbp_Calibration-NAB08.pdf.
Chlorophyll concentration (parameter name chl_a_derived): Chlorophyll fluorescence (parameter name chl_raw) is reported as the raw instrument voltage output minus dark counts (median in situ dark voltage = 0.083 volts). An algorithm to convert chlorophyll fluorescence to chlorophyll concentration (mg chlorophyll m-3) was developed for the R/V Knorr data using an empirical relationship between extracted chlorophyll and the following in-situ measurements: chlorophyll fluorescence, temperature, PAR, depth and time. This relationship is empirical and it should not be applied to the other cruise data without independent verification. For more details see Chlorophyll Calibration document (Chlorophyll_Calibration-NAB08.pdf) and Bagniewski et al. (subm.). Matlab code for calculation of this chlorophyll proxy: chlorophyll_proxy_calculation_NAB08.m.
Surface PAR (parameter name SPAR): Calibration coefficients for surface PAR sensor were incorrect in the original SBE configuration file. The incorrect coefficients were removed in the post processing and correct coefficients were applied to the data. The sensor was new and calibrated before the cruise. For more details, see Radiometry_and_PAR_Calibration-NAB08.pdf.
Water column photosynthetically active radiation (parameter name PAR): Reported values for water column PAR might have a positive bias of ~0.08 µmol photon m^-2 s^-1 based on discrepancies between factory calibration sheet and value used in the SBE configuration file. This error is very small and usually less than or similar to calibration associated error, as noted in the factory calibrations. For more details, see Radiometry_and_PAR_Calibration-NAB08.pdf.
CDOM fluorescence (parameter name CDOM) is reported as raw, uncalibrated values; no calibration or dark values were available for this borrowed sensor.
Broad angle sidescattering at 880 nm (parameter name ss880_raw) is reported as raw, uncalibrated values; no calibration or dark values were available for this sensor.
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