Ocean Carbon and Biogeochemistry: Data System

MedFlux cruise: EN402 March 2005
HPSS CTD profile data processing notes

31 January 2006: Prepared for OCB data system by Terry McKee (PO Dept, WHOI) and Cyndy Chandler, OCB DMO (WHOI).

Details of HPSS CTD data processing steps:

Seabird processed HPSS CTD downtrace data files (*.cnv) were contributed on the CD-ROM that was generated during the cruise and the OCB DMO extracted the data from those files. Data had been processed during the cruise using the standard set of Seabird utilities, to generate final 0.5-decibar pressure sorted downtrace files for all HPSS CTD casts. The only additional processing done by the OCB DMO, was to reformat the at-sea-processed .cnv files (.5db bin-averaged) found in the "seabird/data/list" directory. The *.cnv files had been output in binary format, so we used the SBEDataProcessing program, "Translate", to convert the data to ASCII format. Also, MATLAB Physical Properties of Seawater routines were used to calculate and add several derived oceanographic parameters.

None of the HPSS CTD data has been calibrated with in-situ data, and should therefore be used with caution. The dissolved oxygen data is of poor quality, and nearly all the data recorded from all six Fgp pressure sensors is equal to 1.000. The HPSS CTD casts are noted as "CTD - Christian" in the Cruise Plan. No position information was recorded with the HPSS cast done on 08 March and most of the data were of very poor quality, and therefore were not entered into the database.

EN402 HPSS CTD shipboard data processing notes:

Modified from 402CTDprocessingHPSS.doc file contributed on post-cruise data CD-ROM.

Datcnv

X Process scans to end of file. Scans to skip over 0. Binary output, up& down, Both bottle & data to list. Scans marked with bottle confirm bit. Scan range offset 0. Scan range duration 2. Do not merge separate header file.

Scan Count, Time Elapsed (s), Pressure Digiquartz (db), Depth (m), Temp 1, Cond 1,  V0, V1, V2, V3, V4, V5, V6, V7, Pump Status, Latitude, Longitude, Bottles Fired, FGP Pressure 1, FGP Pressure 2, FGP Pressure 3, FGP Pressure 4, FGP Pressure 5, FGP Pressure 6, Oxygen Current, Oxygen Temp.

Filter for SBE9, old manual.txt suggests Low pass filter B = 0.15s for pressure

            Low pass filter A = 0.03s for conductivity

  New SBEDataProcessing_5.32a.pdf suggests only .15 for pressure

Used: B=0.15 for Press, Depth. A=0.03 for Cond 1 & 2 & Diff

AlignCTD for

DO 4 (2 at 25C, 5 at 0C)   V4, Oxy V pri, V6, OxyV sec

CellTM for 9+ w/TC duct & pump running at 3000rpm. Correct both pri & sec conductivity values

alpha = 0.03

1/beta = 7

LoopEdit (not done for EN402)

  Fixed minimum velocity of 0.25m/s. X Exclude scans marked bad.

Derive

  Depth (sw m), Salinity 1 (PSU), Density 1 (sigma-t, Kg/m^3), Descent Rate (m/s), Oxygen 1 (ml/l), Oxygen Beckman (ml/l)

BinAvg

  Pressure, 0.5, X Incl #scans/bin, X exclude scans marked bad, skip over 0, Process Downcast only, X Incl surface bin 0, 0, 0

ASCII_Out

  Output header & data files, 60 lines/pg, label top of file, semicolon, Julian days, all variables.

BottleSum

  Show Min/Max for Avgd variables, all and Derived: salinity, density, oxygen saturation (ml/l), oxygen Beckman (ml/l)

Processing Summary Files:

Final HPSS CTD station 313 (as in date 050313) header record showing history of processing steps:
EN402_hpss050313_hdr.txt

An HPSS CTD Configuration report representative of all HPSS stations.
CTDConReportHPSS_313.txt

The OCB DMO derived some parameters using MATLAB Physical Properties of Seawater Toolbox:

Depth   [ sw_dpth.m ]

depth=sw_dpth(data.prs,43);   % latitude fixed at 43 ° N

Density   [ sw_dens.m ]

sigma-t=sw_dens(data.ctdsal1,data.ctdtmp1,data.ctdprs,0)-1000;

Potential Density   [ sw_pden.m ]

sigma_0=sw_pden(data.ctdsal1,data.ctdtmp1,data.ctdprs,0)-1000;

Potential Temperature   [ sw_ptmp.m ]

potemp=sw_ptmp(data.ctdsal1,data.ctdtmp1,data.ctdprs,0);