


     GP4-00-KA
     NOAA Ship Ka'imimoana
     Kwajalein, Marshall Islands - Honolulu, HI
     July 17 - August 12, 2000

     Chief Scientist: Mr. Dave Zimmerman
     Survey Department: CST Dennis Sweeney
     CTD Personnel: D. Sweeney
     Final Processing: K. McTaggart


     ACQUISITION: 

     Fifty CTD profiles were collected on this cruise.  Twenty-three
     profiles were collected along 165E from 8N to 8S; and 27 were collected
     along 180 from 8S to 8N and along the ship's trackline to 12N.
     All but one CTD cast were to 1000m, cast 15 was aborted around 200 m
     owing to a bad termination.  Winch cable and drum incompatibilities
     prevented any deep profiles from being collected.  A new spool of cable
     will be installed while in Honolulu.

     The ship's Sea-Bird 9plus CTD s/n 09P10493-0405 measuring pressure (s/n 
     61183), temperature (s/n 2027, 2026), and conductivity (s/n 1537, 1536)
     was used for all casts (PMC19.CON).  

     The CTD was mounted in a custom 24-bottle frame with Sea-Bird rosette 
     sampler s/n 88.  The CTD data stream was passed through Sea-Bird 11plus
     deck unit s/n 376 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 5133 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.  Cruise data were also
     archived on 8 mm tape and CD-ROM.

     Salinity samples were not collected on shallow cast 0151 as it was
     aborted after the termination went bad around 200 m.  Profile data for
     casts 0281 and 0341 had to be replayed from VCR tape, and .BTL files
     created from .BL files.  Cast 0481 was appended from two pieces, 0-500 m
     down and 500 m-surface.
     
     Problems suspect of a poor termination persisted after the cable was 
     reterminated.  Also, hydraulic fluid leaked from the CTD A-frame and
     onto the underwater package on the recovery of cast 0221.  In spite of
     clean up, interconnecting cables and connectors may have been damaged.  


     SALINITIES:

     Seawater was collected at 12 depths each cast and salinity samples drawn.
     Two salinity samples were taken from the deepest Nisken.  Duplicate samples
     were analyzed on a subsequent day from the rest.  Salinity analysis was
     performed using Guildline Autosal 8400B salinometer s/n 61.663.  IAPSO 
     standard seawater batch #P136 dated April, 1999, was used for all casts. 
     Standard laboratory operating temperature was approx 23 degrees Celsius. 


     POST-CRUISE CONDUCTIVITY CALIBRATIONS:

     GP400S.CAL of primary (s/n 2027, 1537) sensor data (not including any
     duplicate salts) was created at sea.  It's completeness and correctness
     were scrutinized and ammended where needed.

     Final pressure and temperature (s/n 2027) calibrations were pre-cruise.
     Drift (0.000209 C) and viscous (-0.0006 C) corrections were applied to
     temperature.  Conductivity fit coefficients were determined using Matlab
     program CALCOS2 since there were no deep bottles:

                        number of points used   395
                        total number of points  521
                        % of points used in fit 75.82
                        fit standard deviation  0.001569
                        fit bias                -0.0014178306
                        min fit slope           1.0000798
                        max fit slope           1.0001711

     Slope, bias, and pressure correction values were applied to CTD data 
     and converted directly into netCDF format using CNV_EPS; and to bottle
     file data using CALMSTR and CLB_EPS. 


     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.

     TRANS converts the data file from binary to ASCII format.  These 
     data are transfered to the PMEL VAX.

     Program CNV_EPS applies post-cruise temperature corrections and
     conductivity calibration coefficients, recomputes the derived variables 
     in DERIVE, and converts the ASCII data files to netCDF format.  CNV_EPS
     skips bad records near the surface (typically the top 3 m) as well as any
     records containing -9.990e-29, and copies back 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, CNV_EPS 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 copied back 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 CALMSTR applies post-cruise temperature corrections and 
     conductivity calibration coefficients and recomputes the derived variables
     in ROSSUM.  CLB_EPS converts the ASCII bottle data file into individual
     cast netCDF data files.  Station 7 sample 111 and station 47 sample 106
     were flagged as questionable.  Station 28 sample 102, 33 sample 102, 
     34 sample 106, and 45 sample 102 were flagged as bad.

     Final CTD and bottle files were moved to DISK$EPIC1:[HAYES.DATA.GP400.CTD] 
     and included in the MySQL data management tables on August 24, 2000.
