


     GP1-02-KA
     NOAA Ship Ka'imimoana
     San Diego, CA - Manzanillo, Mexico
     March 1 - April 4, 2002

     Chief Scientist: Mr. Ben Moore
     Survey Department: AST Amy Frank
     CTD Personnel: AST Amy Frank, Nuria Ruiz 
     Final Processing: K. McTaggart


     ACQUISITION: 

     Seventy-five CTD profiles were collected on this cruise.  Twenty-eight
     profiles were collected from 12N to 8S along 110W.  Forty-seven profiles
     were collected from 8S to 12N along 95W.  The majority of casts were to
     1000 m.  Because several moorings had conductivity sensors on them, 
     additional shallow casts were taken for calibration purposes, 18 to 200 m
     and 3 to 500 m.  There were 9 deep casts.

     PMEL's Sea-Bird 9plus CTD s/n 09P10881-0390 measuring pressure (s/n 
     58950), the ship's temperature sensors (s/n 2027, 2026), and the ship's 
     conductivity sensors (s/n 1537, 1536) were used for the first 16 casts (last
     calibrated in January, 2002).  Primary conductivity sensor s/n 1537 
     developed a hairline fracture in the cell and was replaced with TAO sensor
     s/n 1467 (last calibrated in January, 2002).  This configuration was used
     throughout the rest of the cruise (pmc26.con).

     The CTD was mounted in a custom 24-bottle frame with Sea-Bird rosette 
     sampler s/n 54 and then 88.  The CTD data stream was passed through 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 personal computer equipped with Sea-Bird's SEASOFT Windows
     acquisition software where calibrated data were displayed in fixed listing
     and graphical form in real-time, as well as stored in raw form onto hard 
     disk.  Backups of the raw data were made on Zip disk and CD-ROM and 
     returned to PMEL for post-cruise processing.


     SALINITIES:

     12 samples were taken each cast as usual.  No duplicate samples were taken
     this cruise.  Salinity analysis was performed using Guildline Autosal 8400B
     salinometer s/n 61.667, OSI ACI2000 interface, and IAPSO standard seawater
     batch #P139.  Laboratory operating temperature ranged between 21-24 degrees
     Celcius.

     Salinity analysis was poor.  Bottle salinities tended to be salty of the
     CTD for the entire cruise.


     POST-CRUISE CONDUCTIVITY CALIBRATIONS:

     GP102S.CAL of secondary sensor data (not including any duplicate salts)
     was created at sea during GP202 by K. McTaggart.  It's completeness and 
     correctness were scrutinized and ammended where needed.  Primary sensors 
     s/n 1537 and 1467 were noisier than the secondary sensors 1536 and 2026.

     Final pressure and temperature calibrations were pre-cruise.  A viscous
     heating correction of -0.0006 C and a historical drift correction of
     -0.0009 C were applied to temperature sensor s/n 2026.  

     Conductivity fit coefficients were determined using Matlab program
     CALCOS0.  CALCOP programs were not chosen because of the overall poor
     quality of sample salinity data.  In order not to fit the negative scatter
     in the residuals owing to salty sample readings, the standard deviation
     allowable in the fit was 2.2 instead of 2.8.

                         number of points used   404
                         total number of points  612
                         % of points used in fit 66.01
                         fit standard deviation  0.004161
                         fit bias               -0.020318704
                         min fit slope           1.0006152
                         max fit slope           1.0006152

     Slope and bias correction values were applied to CTD data and converted
     directly into netCDF format using CNV_SHIFT_EPS*; and to bottle file data 
     using CALMSTR and CLB_SHIFT_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.  Both down and up casts
     are processed.

     ROSSUM averages the bottle data specified in the DATCNV output and 
     derives salinity, theta, sigma-t, and sigma-th. Bottle data are used
     to calibrate the CTD post-cruise. 

     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.

     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 (excluding those flagged as bad).  Bottle flagged
     as questionable were station 13 samples 105 and 107, station 15 101, 29
     106, 42 201, 44 103, and 55 204.

     NOTE: When the 9 deep profiles were compared to historical profiles, it
     was apparent that the CTD data were too salty.  The offsets were averaged
     and 0.0050 were subtracted from CTD salinities using CNV_SHIFT_EPS and
     CLB_SHIFT_EPS (in order to compute corrected densities for the files).

     Final CTD and bottle files were moved to /home/plover/hayes/data/gp102/ctd
     and included in the MySQL data management tables on May 8, 2002.
