     GP6-96-KA
     NOAA Ship Ka'imimoana
     San Diego, CA - Manzanillo, Mexico
     September 27 - October 27, 1996

     Chief Scientist: Mr. Paul Freitag
     Survey Department: CST Jim Davis
     CTD Personnel: J. Davis
     Final Processing: K. McTaggart


     ACQUISITION: 

     Thirty-four CTD profiles were collected during this cruise.  Fourteen 
     profiles were collected along 110W from 8N to 8S, and 20 profiles were
     collected along 95W from 8S to 11N.  The majority of casts were to 
     1000 m.  Eight casts were deep (>2500 db) and 2 were 500 m calibration 
     casts for TAO moorings.  

     All casts used 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).  The CTD was mounted in a custom 24-bottle frame with a 
     Sea-Bird rosette sampler.  The CTD data stream was passed through a 
     Sea-Bird 11plus deck unit (s/n 392) 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 the hard disk.  Backups of the raw data were made on QIC-80
     1/4" cartridge tapes and returned to PMEL for post-cruise processing.

     Sea-Bird rosette s/n 54 (PMEL) had mechanical difficulties and was 
     replaced with PMC rosette s/n 88 prior to station 3.


     SALINITIES:

     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 the bottle salinities used to calibrate this data set, only a 
     drift-during-run linear interpolation correction.  Standard operating 
     temperature was 24 degrees Celsius.
 

     POST-CRUISE CONDUCTIVITY CALIBRATIONS:

     GP696AS.CAL, including duplicate salts, was created at sea using program 
     SBECAL.  Anomalous differences between CTD and bottle salinities were 
     scrutinized.  Bottle salinities were checked against their original log 
     sheets for typos.  Only one bottle salt exists for station 2 owing to 
     mechanical failure of the rosette sampler.  GP696BS.CAL was created at 
     the lab.  It differs from GP696AS.CAL in that the NRCC calibration 
     correction of 0.001 has been removed from the bottle salinities.

     Final pressure and temperature calibrations were pre-cruise.  
     Conductivity calibration coefficients were best determined using a 
     station-dependent fourth-order fitting routine, CALCOS4, written by 
     Greg Johnson in MATLAB.

          number of points used   237
	  total number of points  252
	  % of points used in fit 94.05
	  fit standard deviation  0.001339
	  fit bias -0.0093763531 mS/cm
	  min fit slope 1.0004883
	  max fit slope 1.0006705

     Slope and bias values were applied to CTD data using PMEL Fortran program
     GP696_EPIC; and to bottle files using CALMSTR6.


     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 program GP696_EPIC applies post-cruise conductivity calibration 
     coefficients, recomputes the derived variables in DERIVE, and converts
     the ASCII data files to EPIC format.  GP696_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, GP696_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 CALMSTR46 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.
     The following bad bottle data were omitted: station 30 cast 1 bottle 6.

     Final CTD and bottle files were moved to DISK$EPIC1:[HAYES.DATA] and 
     included in the RIM data management tables on February 19, 1997.  
