


     GP5-97-KA
     NOAA Ship Ka'imimoana
     Manzanillo, Mexico - San Diego, CA
     July 31 - August 29, 1997

     Chief Scientist: Mr. Paul Freitag
     Survey Department: CST Dennis Sweeney
     CTD Personnel: D. Sweeney, M. Fowler
     Final Processing: K. McTaggart


     ACQUISITION: 

     Thirty-three CTD profiles were collected on this cruise.  A 1000 m test 
     cast was made during the transit from Honolulu to Manzanillo.  This test
     cast was not processed.  Seventeen CTD casts were made along 95W from 8N 
     to 8S.  One cast was taken at 8S, 102W.  Fifteen profiles were collected 
     along 110W from 8S to 11N.  The majority of CTD casts were to 1000 m; 
     four were to 500 m, and only one was deep (>3000 db).

     The ship's Sea-Bird 9plus CTD s/n 09P10493-0405 measuring pressure (s/n 
     61183), temperature (s/n 1708, 2027), and conductivity (s/n 1536, 1537)
     (PMC8.CON) was used for casts 1 and 2.  Primary conductivity sensor s/n 
     1467 (PMC9.CON) was substituted for casts 3-5.  PMEL Sea-Bird CTD s/n 
     09P10881-390 with pressure s/n 58950 and same TC pairs (PMEL2.CON) was 
     used for casts 6-13.  Secondary conductivity sensor s/n 1469 (PMEL3.CON)
     was substituted for casts 14-32.

     The CTD was mounted in a custom 24-bottle frame with a Sea-Bird rosette 
     sampler (s/n 88 for casts 1-10 and s/n 54 for casts 11-32).  The CTD data
     stream was passed through a Sea-Bird 11plus deck unit (s/n 392 for casts
     1-7 and s/n 396 for casts 8-32) 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 hard disk.  Backups of the raw data were made on QIC-80 1/4" 
     cartridge tapes and returned to PMEL for post-cruise processing.

     Data were problematic during this entire cruise.  Noise in all channels
     led to 300 m of winch cable being cut off and reterminated.  (NOTE: cable
     was damaged at 500 m at the end of GP497; ship was advised by the lab to 
     cut off at least 500 m of cable.)  Noise persisted in the primary (CTD s/n
     405) and then the secondary (CTD s/n 390) conductivity and sometimes temp-
     erature channels.  Some rosette positions were consistently not firing, 
     likely owing to the use of WD-40 (even though the ship was advised by Sea-
     Bird and the lab not to use anything but fresh water on the carousel).  
     All three pumps were damaged, likely owing to the deck units being left 
     on between casts running the pumps on deck as the Triton-X storage 
     solution had become contaminated with salt water.  

     Both 9plus CTDs, both rosette carousels, all three pumps, and two 
     conductivity sensors were sent to Sea-Bird after this cruise for inspection
     repair, and calibration.  
    

     SALINITIES:

     For calibration purposes, bottle samples were usually taken at at least
     6 depths on 1000 m or shallower casts and at at least 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 #P130 was used for all casts.  NRCC calibrations were not 
     applied to this data set, only a drift-during-run linear interpolation 
     correction in ship program DISAL.  Standard operating temperature was 
     around 25.5 degrees Celsius.
 

     POST-CRUISE CONDUCTIVITY CALIBRATIONS:

     GP5972S.cal of secondary sensor data for casts 1-5 and GP5971S.CAL of 
     primary sensor data for casts 6-32 (not including any duplicate salts) was 
     created post-cruise using modified program SBECAL.  Anomalous differences 
     between CTD and bottle salinities were scrutinized.

     Final pressure and temperature calibrations were pre-cruise.  Conductivity
     fit coefficients were determined for each .CAL file using Matlab programs.
     For GP5972S.CAL, the best fit was determined using a second order station-
     dependent fitting routine, CALCOS2.

    			number of points used   28
	    		total number of points  33
	  		% of points used in fit  84.85
	  		fit standard deviation  0.002317
	  		fit bias -0.031347916 mS/cm
	  		min fit slope 1.0012617
	  		max fit slope 1.0015644 


     For GP5971S.CAL, the best fit was determined using a third order station-
     dependent fitting routine, CALCOS3.

    			number of points used   125
	    		total number of points  143
	  		% of points used in fit  87.41
	  		fit standard deviation  0.001983
	  		fit bias -0.0048694115 mS/cm
	  		min fit slope 0.99989947
	  		max fit slope 0.999997

     Slope and bias values were applied to CTD data using PMEL Fortran programs
     GP5972_EPIC and GP5971_EPIC; and to bottle files using CALMSTR5.


     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 GP597n_EPIC applies post-cruise conductivity calibration 
     coefficients, recomputes the derived variables in DERIVE, and converts
     the ASCII data files to EPIC format.  GP597n_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, GP597n_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.

     Data from station 12 did not come back to the lab.  The following casts
     were truncated:  0011 at 3338 db, 0091 at 916 db, 0181 at 168 db, 0191 at
     338 db.  A 5-point spike was removed from cast 0291 at 839-843 db.

     PMEL program CALMSTR5 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.
     Station 0011 samples 109 and 112, and station 0141 sample 103 were flagged
     as bad and removed from the EPIC bottle files.  There are no .BOT files 
     for stations 0121 and 0221.

     Final CTD and bottle files were moved to DISK$EPIC1:[HAYES.DATA] and 
     included in the RIM data management tables on September 22, 1997.
