Ocean Carbon and Biogeochemistry: Data System

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MedFlux cruise: EN402 March 2005
CTD profile data processing notes

PI: Cindy Lee (SUNY Stony Brook)

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

Details of CTD data processing steps:

Seabird processed 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 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 "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.

EN402 CTD shipboard data processing notes:

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

CTD001 a Benthos Altimeter was installed.

CTD002-011 a WET Labs ECO Fluorometer was installed and Altimeter removed.

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 seawater (m), Temp 1, Temp 2, Temp Diff, Cond 1, Cond 2, Cond Diff, V0, V1, V3, Beam Attenuation Seatech, Beam Transmission Seatech, Fluorescence Seatech, Fluorescence WETLab ECOFL, V4, Oxygen V SBE43 1, V6, Oxygen V SBE43 2, Pump Status, Latitude, Longitude, Bottles Fired.

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

  Cond 0.073s (secondary only)

  Temp 0

  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 & 2 (PSU), Density 1 & 2 (sigma-t, Kg/m^3), Descent Rate (m/s), Oxygen 1 & 2 (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 salinity, density, oxygen (ml/l) derived


Processing Summary Files:

Final CTD station 11 header record showing history of processing steps:
EN402_ctd011_hdr.txt

CTD Configuration report stations 1 - 11:
CTDConReport402.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);