


     GP1-98-KA
     NOAA Ship Ka'imimoana
     San Diego, CA - San Diego, CA
     February 5 - March 13, 1998

     Chief Scientist: Mr. Mark Ablondi
     Survey Department: CST Dennis Sweeney
     CTD Personnel: D. Sweeney, Matt Fowler, Jason Kahn
     Final Processing: K. McTaggart


     ACQUISITION: 

     Thirty-five CTD profiles were collected on this cruise.  Seventeen CTD 
     profiles were collected along 95W from 8N to 8S; seventeen along 110W 
     from 8N to 8S; and one test cast enroute to the first station (not
     processed).  The majority of CTD casts were to 1000 m; 2 were to 500 m, 
     and 4 were to 3500 m.

     The ship's Sea-Bird 9plus CTD s/n 09P10493-0405 measuring pressure (s/n 
     61183), temperature (s/n 2026, 2027), and conductivity (s/n 1536, 1537)
     (PMC10.CON) was used for all casts.  

     The CTD was mounted in a custom 24-bottle frame with Sea-Bird rosette 
     sampler s/n 88.  The CTD data stream was passed through Sea-Bird 11plus
     deck unit s/n 376 with factory settings.  An analog signal was recorded 
     onto the audio portion of VCR tape as a backup.  Digitized data were sent
     to a Dell 4100 personal computer equipped with Sea-Bird's SEASOFT 
     acquisition software (version 4.216) where calibrated data were displayed 
     in graphical form in real-time, as well as stored in raw form onto hard 
     disk.  Backups of the raw data were made on QIC-80 1/4" cartridge tapes 
     and returned to PMEL for post-cruise processing.

     Station 5 was shortened to a depth of 845 m due to the close proximity
     of another vessel.  Seven bottles were closed during the upcast.  Stations
     6 and 10 downcast data were generated from VCR backup.  The replay of 
     station 6 was unuseable.  There are no bottle salts for station 13 because
     the bottles were inadvertantly reused before the samples were analyzed.  
     No Niskin samples were collected during station 31 owing to vent caps left
     open.  


     SALINITIES:

     MBARI requested 8 bottles be tripped between 200 m and the surface.  The
     remaining 4 bottles were used for calibration purposes.  Two salinity 
     samples were taken from the deepest Niskin.  Duplicate samples were 
     analyzed on a subsequent day from the rest.  Salinity analysis was 
     performed using Guildline Autosal 8400B salinometer s/n 61.383 (last 
     calibrated at NRCC February 13, 1996).  IAPSO standard seawater batch 
     #P127 was used for all casts.  NRCC calibrations were not applied to this
     data set, only a drift-during-run linear interpolation correction in ship
     program DISAL.  Standard laboratory operating temperature was approx 26 
     degrees Celsius.
 

     POST-CRUISE CONDUCTIVITY CALIBRATIONS:

     GP198S.CAL of primary sensor data (not including any duplicate salts) was 
     created at sea.  It's completeness and correctness were scrutinized and 
     ammended where needed.  All data were used in the fit as one group.

     Final pressure and temperature calibrations were pre-cruise.  Conductivity
     fit coefficients were determined using Matlab programs.  Station-dependent 
     fits (CALCOSn) were tried using all the bottles.  Residuals verses pressure
     showed a non-linear trend.  CALCOPn programs helped but didn't correct the
     problem.  Also, none of the fitting routines used more than 70% of the data.
     It was suggested that the TC pairs be recalibrated at Sea-Bird before the 
     next cruise.  CALCOP2 gave these final results:

        Stations 1-34:  number of points used   260
		     	total number of points  376
			% of points used in fit 69.15
			fit standard deviation  0.001494
			fit bias                -0.02168033
			fit co pressure fudge   9.0721519e-007
			min fit slope           1.0007042
			max fit slope           1.0007459

     Slope, bias, and pressure correction values were applied to CTD data using 
     PMEL Fortran program GP198_EPIC; and to bottle file data using CALMSTR1.


     FINAL PROCESSING:

     The following are the standard SEASOFT processing modules used to reduce 
     Sea-Bird CTD data:

     DATCNV converts raw data to engineering units and creates a bottle
     file if a Sea-Bird rosette sampler was used.  (MARKSCAN creates a 
     bottle file if a General Oceanics rosette was used.)

     ROSSUM averages the bottle data specified in the DATCNV or MARKSCAN
     output and derives salinity, theta, sigma-t, and sigma-th.  These
     bottle files are transfered to the PMEL VAX where post-cruise 
     calibrations are computed.

     WILDEDIT makes two passes through the data in 100 scan bins.  The
     first pass flags points greater than 2 standard deviations; the
     seond pass removes points greater than 20 standard deviations from
     the mean with the flagged points excluded.

     CELLTM uses a recursive filter to remove conductivity cell thermal
     mass effects from the measured conductivity.  In areas with steep
     temperature gradients the thermal mass correction is on the order
     of 0.005 psu.  In other areas the correction is negligible.  The
     value used for the thermal anomaly amplitude (alpha) is 0.03.  The
     value used for the thermal anomaly time constant (1/beta) is 9.0.
 
     FILTER applies a low pass filter to pressure with a time constant of
     0.15 seconds, and to conductivity with a time constant of 0.03 seconds.
     In order to produce zero phase (no time shift) the filter is first
     run forward through the file and then run backwards through the file.

     LOOPEDIT removes scans associated with pressure slowdowns and
     reversals.  If the CTD velocity is less than 0.25 m/s or the pressure
     is not greater than the previous maximum scan, the scan is omitted.

     BINAVG averages the data into 1 db bins.  Each bin is centered around
     a whole pressure value, e.g. the 1 db bin averages scans where pressure
     is between 0.5 db and 1.5 db.

     DERIVE uses 1 db averaged pressure, temperature, and conductivity to
     compute salinity, theta, sigma-t, sigma-th, and dynamic height.

     SPLIT removes decreasing pressure records and keeps only the downcast
     data.

     TRANS converts the data file from binary to ASCII format.  These 
     data are transfered to the PMEL VAX.

     PMEL programs GP198_EPIC applies post-cruise conductivity calibration 
     coefficients, recomputes the derived variables in DERIVE, and converts
     the ASCII data files to EPIC format.  GP198_EPIC skips bad records 
     near the surface (typically the top 5 m) as well as any records containing 
     -9.990e-29, and extrapolates raw data to the surface (0 db) within 10 db.  
     Because the SBE module LOOPEDIT does not handle package slowdowns and 
     reversals well in the thermocline where gradients are large, GP198_EPIC 
     removes raw data records where a sigma-theta inversion is greater than 
     -0.01 kg/m3.  Data are linearly interpolated such that a record exists
     for every 1 db.  When data are extrapolated to the surface, the WOCE
     quality word is '888'; when interpolated over greater than 2 db, the 
     WOCE quality word is '666'.  The WOCE quality word consists of a 1-digit
     flag for pressure, temperature (ITS-90), and salinity.

     PMEL program CALMSTR1 applies post-cruise conductivity calibration
     coefficients and recomputes the derived variables in ROSSUM.  EPICBOMSTR
     converts the ASCII bottle data file into individual cast EPIC data files.
     Bad bottle salts were flagged in GP198S.CLB and removed from their
     .BOT files for station 8 sample 107, station 10 sample 104, station 12
     sample 110, station 17 sample 102, station 18 sample 103, and station 28
     samples 107 and 108.

     Final CTD and bottle files were moved to DISK$EPIC1:[HAYES.DATA.GP198.CTD] 
     and included in the RIM data management tables on March 25, 1998.
