


     GP8-99-RB
     NOAA Ship Ronald H. Brown
     Seattle, WA - San Diego, CA
     November 11 - December 2, 1999

     Chief Scientist: Mr. Andy Shepherd
     Survey Department: CST Jonathan Shannahoff
     CTD Personnel: J. Shannahoff, L. Glover
     Final Processing: K. McTaggart


     ACQUISITION: 

     Fifty-one CTD profiles were collected on this cruise.  Twenty-three CTD
     profiles were collected along 110W from 8N to 8S; 28 were collected
     along 95W from 8S to 12N.  The majority of CTD casts were to 1000 m;
     only 3 were deep; none shallow. 

     PMEL's Sea-Bird 9plus CTD s/n 09P8431-0315 measuring pressure (s/n 
     53960), temperature (s/n 1370, 1455), and conductivity (s/n 1177, 1180)
     was used for all casts (TAO9907.CON).  

     The CTD was mounted in a 24-bottle frame with PMEL's Sea-Bird carousel
     s/n 53.  The CTD data stream was passed through PMC 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
     the ship's Gateway G6-200 personal computer equipped with SEASAVE for
     Windows 95/NT (version 1.03) and DOS SEASOFT acquisition software (version
     where calibrated data were displayed in graphical and fixed forms in real-
     time, as well as stored in raw form onto hard disk.  Backups of the raw
     data were made on Zip disks and CD-ROM and returned to PMEL for post-
     cruise processing.

     Cast 28 and 49 (0-866 db) data were recovered from VCR tape post-cruise.


     SALINITIES:

     Twelve Niskens were fired each cast.  Salinity analysis was performed
     using Guildline Autosal 8400B salinometer s/n 61.668 (aka Dallas).  IAPSO 
     standard seawater batch #P134 was used for all casts.  Salinity values 
     were computed interactively using Sea-Bird's SEACALC utility.  Standard
     laboratory operating temperature was approx 24 degrees Celsius.


     POST-CRUISE CONDUCTIVITY CALIBRATIONS:

     GP899S.CAL of primary sensor data and GP8992S.CAL of secondary sensor data
     were created at PMEL post-cruise.  Residual plots of CTD-bottle conductivities
     revealed the secondary conductivity sensor to be more stable (no jumps) and
     in better health than the primary sensor (offset by -0.01 mS/cm).  Final
     pressure and secondary temperature calibrations were pre-cruise.  Drift
     (0.0000262 C) and viscous (-0.0006 C) corrections were applied to secondary
     temperature.  Secondary conductivity fit coefficients were determined using
     Matlab program CALCOS0:

			number of points used   490
			total number of points  584
			% of points used in fit 83.9
			fit standard deviation  0.002210
			fit bias                -0.016829929
			fit slope               1.0004461

     Slope, bias, and pressure correction values were applied to CTD data using 
     PMEL Fortran program GP899_EPIC; and to bottle file data using CALMSTR8.


     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 GP899_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.  GP899_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, GP899_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 CALMSTR8 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.  Station 33 sample 120 was flagged as questionalbe.

     Final CTD and bottle files were moved to DISK$EPIC1:[HAYES.DATA.GP899.CTD] 
     and included in the RIM data management tables on January nn, 2000.
