


     GP1-96-MB
     NOAA Ship Malcolm Baldrige
     Rodman, Panama - Hilo, Hawaii
     May 3 - 31, 1996

     Chief Scientist: Mr. D. Zimmerman
     Survey Department: CST D. Sweeney
     CTD Personnel: A. Nimersheim, Ship's Survey Department
     Final Processing: K. McTaggart, M. O'Haleck


     ACQUISITION: 

     Thirty-six CTD profiles were collected during this cruise covering 
     two meridionals from 8N to 8S.  Nineteen profiles were collected along 
     95W, and 17 along 110W.  The majority of casts were to 1000 m; 5 casts 
     were deep (3000 db).  

     All casts used TAO's Sea-Bird 9plus CTD s/n 09P10881-0390 measuring 
     pressure (s/n 58950), temperature (s/n 1708 or 1710), and conductivity 
     (s/n 1467).  The CTD was mounted in a 12-bottle frame with a Sea-Bird 
     rosette sampler (s/n 54).  The CTD data stream was passed through AOML's 
     Sea-Bird 11plus deck unit.  An analog signal was recorded onto the audio 
     portion of VCR tape as a backup.  Digitized data were sent to a personal 
     computer equipped with Sea-Bird's SEASOFT acquisition software (version
     4.209) 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 Syquest 200 Mbyte tapes and returned to PMEL
     for post-cruise processing.


     SALINITIES:

     Salinity analysis was performed using Guildline Autosal salinometer
     s/n ??? (last calibrated ???) and IAPSO standard seawater batch #P129.
     Instrument 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:

     GP196A.CAL was created at PMEL using program SBECAL.  Anomalous 
     differences between CTD and bottle salinities were scrutinized.
     Bottle salinities were checked against their original log sheets 
     for typos.  Station 1 was aborted at 40 db so there were no bottle 
     data for this cast.

     Final pressure and temperature calibrations were pre-cruise.  
     Conductivity calibration coefficients were best determined using a 
     station-dependent second-order fitting routine, CALCOS2, written by 
     Greg Johnson in MATLAB on the following groups.  

          Stations 2-14:  number of points used  117  
			  total number of points  130
			  % of points used in fit 90
			  fit standard deviation  0.00191
			  fit bias  0.0030983449 mS/cm
			  min fit slope  1.0000148
			  max fit slope  1.0000252

	  Stations 15-19: number of points used  44 
			  total number of points  50
			  % of points used in fit 88
			  fit standard deviation  0.001934
			  fit bias  0.0061918306 mS/cm
			  min fit slope  0.99984193
			  max fit slope  0.99987277

	  Stations 20-27: number of points used  58
			  total number of points  70
			  % of points used in fit 82.86
			  fit standard deviation  0.001885
			  fit bias  -0.0020791189 mS/cm
			  min fit slope  1.0002017
			  max fit slope  1.0002687

	  Stations 28-36: number of points used  80
			  total number of points  88
			  % of points used in fit 90.91
			  fit standard deviation  0.002486
			  fit bias  0.00063163251 mS/cm
			  min fit slope  1.0000853
			  max fit slope  1.0001812
   
     Slope and bias values were applied to CTD data using PMEL Fortran program
     GP196_EPIC; and to bottle files 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 program GP196_EPIC applies post-cruise conductivity calibration 
     coefficients, recomputes the derived variables in DERIVE, and converts
     the ASCII data files to EPIC format.  Sea-Bird .CNV files are editted 
     to remove bad records near the surface (typically the top 3 m) and any 
     causing spikes in the deeper water column before running GP196_EPIC.
     GP196_EPIC 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, GP196_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 interpolated over greater than 2 db, the 
     WOCE quality word is '666'.

     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 bottles that were not included in EPIC bottle files were station 21
     bottle 5, station 24 bottle 6, station 30 bottle 5, and station 32 bottle
     4.

     Final CTD and bottle files were moved to DISK$EPIC1:[HAYES.DATA] and 
     included in the RIM data management tables on September 30, 1996.  
