


     GP6-02-RB
     NOAA Ship Ronald H. Brown
     Panama City - Panama City, Panama
     October 8 - November 8, 2002

     Chief Scientist: Mr. Patrick A'hearn
     Survey Department: CST Jonathan Shannahoff
     CTD Personnel: CST Shannahoff, Scott McKeever (salinities)
     Final Processing: K. McTaggart


     ACQUISITION: 

     Forty-five CTD profiles were collected during this cruise.  Twenty-nine  
     profiles were collected from 12N to 8S along 95W.  A shallow cast was 
     taken at approximately 6S, 106.5W after the recovery of the 5S 95W drifter.
     Then 15 profiles were collected from 8S to 8N along 110W.  Three casts
     were deep (3000 m), 7 were shallow, and the rest were to 1000 m.

     PMEL's Sea-Bird 9plus CTD s/n 09P8431-0315 measuring pressure (s/n
     53960), temperature sensors (s/n 1455, 1370), and conductivity sensors
     (s/n 1177, 1180) were used for all casts.

     The CTD was mounted in a custom 24-bottle frame with Sea-Bird rosette
     sampler s/n 163.  The CTD data stream was passed through Sea-Bird 11plus
     deck unit s/n 367 (ship's) with factory settings.  An analog signal was
     recorded onto the audio portion of VCR tape as a backup.  Digitized data
     were sent to the ship's Gateway G6-200 personal computer equipped with
     Sea-Bird's SEASAVE for Windows acquisition software (Win32 v5.25) 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
     Zip disks and CD-ROM and returned to PMEL for post-cruise calibration and
     processing.

 
     SALINITIES:

     Six samples were taken each cast for the majority of the casts.  For 4 casts
     12 samples were taken.  Salinity analysis was performed using Guildline 
     Autosal 8400B salinometer s/n 61.668 (aka Dallas) and new Ocean Scientific
     International Autosal computer interface, ACI2000.  IAPSO standard seawater
     batch #P139 (Nov, 2000) was used for all casts.  Analysis was performed by
     balloon guy Scot McKeever.  Laboratory operating temperature is assumed to
     have been 24 degrees Celsius.  Overall, the data are noisy and considered
     less stable than the CTD.


     POST-CRUISE CONDUCTIVITY CALIBRATIONS:

     Primary and secondary sensors tracked each other well during the cruise.
     There was no significant difference in calibrating one pair over the other,
     and so the primary pair were processed.  Historically though, primary
     temperature sensor s/n 1455 has a slower drift rate than s/n 1370.
     Final pressure and temperature calibrations were pre-cruise.  A viscous
     heating correction of -0.0006 C and a historical drift correction of
     0.0002 was applied to temperature sensor s/n 1455.  

     Conductivity fit coefficients were determined using Matlab program
     CALCOS0.  CALCOP programs did not better the fit.

                         number of points used   211
                         total number of points  240
                         % of points used in fit 87.92
                         fit standard deviation  0.003951
                         fit bias               -0.021268544
                         min fit slope           1.0006256
                         max fit slope           1.0006256

     Slope and bias 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.  Both down and up casts
     are processed, as well as primary and secondary temps and conds.

     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. 

     ALIGNCTD advances secondary conductity by 0.073 seconds.  The deck
     unit does this automatically for primary conductivity.

     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.

     FILTER applies a low pass filter to pressure with a time constant of
     0.15 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.

     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 7.0.
 
     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.

     The upcast profile was used for casts 0231, 0261, and 0351 because each
     was missing the beginning of the downcast profile ranging from 10-150 db.

     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).  The following
     bottles were flagged as bad and omitted from their bottle files: cast 
     2 sample 106, cast 4 sample 106, cast 7 102, cast 10 106, and cast 22 107.
     Cast 27 sample 107 and cast 40 sample 108 were flagged as questionable.

     Final CTD and bottle files were moved to /plover/insitu2/DATA/hayes/gp602
     and included in the MySQL data management tables on November 27, 2002.
