


     GP1-97-KA
     NOAA Ship Ka'imimoana
     Manzanillo, Mexico - San Diego, CA
     February 3 - March 5, 1997

     Chief Scientist: Ms. Margie McCarty
     Survey Department: CST Jim Davis, GVA Leslie Ross (in training)
     CTD Personnel: J. Davis, L. Ross, M. McCarty
     Final Processing: K. McTaggart


     ACQUISITION: 

     Thirty-four CTD casts were proposed in the final project instructions.
     Due to time restraints owing to mooring operations, CTDs at non-mooring
     sites were omitted and a couple 1000 m casts were shortened to 500 m.
     Therefore fourteen CTD profiles were collected during this cruise.  Six 
     profiles were collected along 95W from 8N to 8S, and 8 profiles were 
     collected along 110W from 8S to 8N.  The majority of casts were to 1000 m
     but two were to 500 m and three were deep (>3000 db).

     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 
     1467, 1537).  The CTD was mounted in a custom 24-bottle frame with a 
     Sea-Bird rosette sampler (s/n 88).  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.


     SALINITIES:

     For calibration purposes, bottle samples were taken at 6 depths on 1000 m
     or shallower casts and at 10 depths during deep casts.  Two bottle samples
     were taken at the deepest depth.  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 removed from the bottle salinities post-
     cruise and not used to calibrate this data set, only a drift-during-run 
     linear interpolation correction in ship program DISAL.  Standard operating 
     temperature was 27 degrees Celsius.
 

     POST-CRUISE CONDUCTIVITY CALIBRATIONS:

     GP197S.CAL, including duplicate salts, was created at sea using batch
     routine MAKECAL.  Anomalous differences between CTD and bottle salinities
     were scrutinized.  Bottle salinities were checked against their original 
     log sheets for typos.  Another version of GP197S.CAL was created at the 
     lab.  It differs from the original in that the NRCC calibration correction
     has been removed from the bottle salinities and a misfire appeared at
     station 8.

     Final pressure and temperature calibrations were pre-cruise.  There
     appeared to be a calibration shift in the pre-cruise conductivity residual
     plots between lines 95W and 110W during 3 1/2 days of transit.  Therefore
     fit coefficients were determined for two groups: stations 1-6 and 7-14.
     Conductivity calibration coefficients were best determined for stations 1-6
     using a first order station-dependent fitting routine, CALCOS1, written
     by Greg Johnson in MATLAB.  Conductivity calibration coefficients were 
     best determined for stations 7-14 using a second order station-dependent 
     fitting routine, CALCOS2.

     Stations 1-6:	number of points used   39
	    		total number of points  40
	  		% of points used in fit 97.5
	  		fit standard deviation  0.002087
	  		fit bias -0.025678563 mS/cm
	  		min fit slope 1.0009262
	  		max fit slope 1.0009638 

     Stations 7-14:	number of points used   56
	    		total number of points  59
	  		% of points used in fit 94.92
	  		fit standard deviation  0.001931
	  		fit bias -0.023852768 mS/cm
	  		min fit slope 1.0009401
	  		max fit slope 1.0010155 

     Slope and bias values were applied to CTD data using PMEL Fortran program
     GP197_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 GP197_EPIC applies post-cruise conductivity calibration 
     coefficients, recomputes the derived variables in DERIVE, and converts
     the ASCII data files to EPIC format.  GP197_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, GP197_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.
     The following bad bottle data were omitted: station 7 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 June 11, 1997.
