


     GP6-98-RB
     NOAA Ship Ronald H. Brown
     Seattle, WA - Balboa, Panama
     October 13 - November 14, 1998

     Chief Scientist: Mr. John Shanley
     Survey Department: SST Jonathan Shannahoff
     CTD Personnel: J. Shannahoff, K. Angstadt
     Final Processing: K. McTaggart


     ACQUISITION: 

     Thirty-eight CTD profiles were collected on this cruise.  A test
     cast was made at 11N, 113W enroute to the 110W line.  Sixteen CTD 
     profiles were collected along 110W from 8N to 8S; and 21 were 
     collected along 95W from 8S to 8N.  The majority of CTD casts
     were to 1000 m; three were deep to 3000 m and 3 shallow (<200 m).  

     The ship's Sea-Bird 9plus CTD s/n 09P9852-0382 measuring pressure (s/n 
     58955), temperature (s/n 1713, 2378), and conductivity (s/n 1473, 1921)
     was used for all casts.  Both TC pairs were calibrated just prior to 
     this cruise.  

     The CTD was mounted in the ship's 12-bottle frame with Sea-Bird rosette 
     sampler s/n 37.  The CTD data stream was passed through Sea-Bird 11plus
     deck unit s/n 367 with factory settings.  An analog signal was recorded 
     onto the audio portion of VCR tape as a backup.  Digitized data were sent
     to a Gateway G6-200 personal computer equipped with Sea-Bird's SEASOFT 
     Windows software (version 1.03) 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 Zip disk and CD-ROM disk 
     and returned to PMEL for post-cruise processing. 


     SALINITIES:

     MBARI requests 8 bottles be tripped between 200 m and the surface.  The
     remaining 2 bottles were used for calibration purposes.  Positions 3 and
     9 couldn't be fired due to the placement of the hanging bail.  There were
     no duplicate samples taken.  Salinity analysis was performed using a
     Guildline salinometer s/n 61668 and IAPSO standard seawater batch #P133. 
     The autosalinometer was standardized with each cast of samples; no drift
     was applied.


     POST-CRUISE CONDUCTIVITY CALIBRATIONS:

     GP698S.CAL of primary sensor data and sample salinities was created post- 
     cruise.

     Final pressure and temperature calibrations were pre-cruise.  A viscous 
     heating correction of -0.0006 C was applied to temperature.  Conductivity
     fit coefficients were determined using Matlab programs CALCOPn:

     Stations 1-18 Calcop3:  number of points used   120
			     total number of points  151
			     % of points used in fit 79.47
			     fit standard deviation  0.00127
			     fit bias                -0.014603804
			     fit co pressure fudge   3.7086808e-006
			     min fit slope           1.000187
			     max fit slope           1.0002701

     Stations 19-35 Calcop2: number of points used   138
			     total number of points  181
			     % of points used in fit 76.24
			     fit standard deviation  0.001378
			     fit bias                -0.01127753
			     fit co pressure fudge   9.4984781e-007
			     min fit slope           1.0002516
			     max fit slope           1.0003121

     Slope, bias, and pressure correction values were applied to CTD data using 
     PMEL Fortran program GP698_EPIC; and to bottle file data 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 programs GP698_EPIC applies post-cruise temperature corrections and
     conductivity calibration coefficients, recomputes the derived variables 
     in DERIVE, and converts the ASCII data files to EPIC format.  GP698_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, GP698_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.  Program GP698_SEC was used to process secondary sensor data 
     for station 26 cast 1 with pre-cruise temperature and conductivity cals.

     PMEL program CALMSTR6 applies post-cruise temperature corrections and 
     conductivity calibration coefficients and recomputes the derived variables
     in ROSSUM.  EPICBOMSTR converts the ASCII bottle data file into individual
     cast EPIC data files.  There were many bad salts flagged in GP698S.CLB:
     station 22 sample 106, 23 sample 202, 26 sample 207, 27 sample 111, 28
     samples 108 and 110, 29 sample 102, and 29 sample 208.  These bottle data
     were not included in the EPIC .BOT files.

     Final CTD and bottle files were moved to DISK$EPIC1:[HAYES.DATA.GP698.CTD] 
     and included in the RIM data management tables on December 14, 1998.
