



     GP6-05-KA
     NOAA Ship RONALD H. BROWN
     Arica, Chile - Panama
     October 26 - November 28, 2005

     Chief Scientist: Andy Shepherd
     Survey Department: CST Jonathan Shannahoff
     CTD Personnel: CST Jonathan Shannahoff
     Final Processing: Kristy McTaggart


     ACQUISITION:

     Thirty-three CTD profiles were collected at 32 stations during this cruise.
     Nineteen profiles were collected from 8S to 5N along 95W; 14 profiles
     were collected from 2N to 8S along 110W.  The majority of casts were to 
     1000m, and 2 casts were deep (3000m).

     PMEL's Sea-Bird 9plus CTD s/n 93450-209 (pressure s/n 53586) was used
     for all casts during this cruise, along with primary temp sensor s/n 1370 
     and primary cond sensor s/n 1180, and secondary temp sensor s/n 1455 and 
     secondary cond sensors s/n 1177 (casts 1-12) and s/n 1473 (casts 13-32).  
     
     The CTD was mounted in the PMEL yellow 24-bottle frame with TAO SBE 
     carousel pylon s/n 407.  The CTD data stream was passed through the ship's 
     11plus deck unit s/n 367 with factory settings.  Digitized data were sent
     to the ship's acquisition PC equipped with Sea-Bird's SEASOFT Windows 
     software version 5.35.  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 100 Mb Zip disks and later on CDs.


     SALINITY SAMPLES:
   
     Salinity analysis was performed using Guildline Autosal 8400B salinometer 
     s/n 61.668, Ocean Scientific ACI2000, and IAPSO standard seawater batch #P145
     dated July 2004.  The bath temperature was set to 24 degrees Celsius.  Eight
     samples are collected per whole-degree cast.  Raw data were archived along 
     with CTD data on CD.  

     At PMEL, ACI2000 .dat files were ammended in Excel such that only 1 header
     line, 1 standard correction line, and 3 salinity lines per sample were
     included in the file.  Corrected salinity values were fixed to 4 decimal
     places and the file overwritten in the NT folder as a space delimited file.


     CONDUCTIVITY CALIBRATION:
   
     GP605S.CAL of primary sensor data (te 1370, co 1180) was created   
     and used to calibrate stations 1-32.

     Final pressure and temperature calibrations were pre-cruise.  A viscous
     heating correction of -0.0006 C and a drift correction of +0.00156 was 
     applied to temperature sensor s/n 1370.

     The best conductivity calibration results were from an overall fit 
     determined by CALCOS2:

     number of points used   160
     total number of points  200
     % of points used in fit 80
     fit standard deviation  0.001396
     fit bias                -0.010261373
     min fit slope           1.0003376
     max fit slope           1.000457

     Slope and bias correction values were applied to CTD burst data using 
     CALMSTR.  Calibrated data were converted into NetCDF format using CLB_EPS 
     on PC Pacific.  Final calibrations were applied to profile data and
     converted into NetCDF format using a local version of CNV_EPS1.


     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, and sigma-theta. Bottle data are used
     to calibrate the CTD and O2 sensor 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.  Data were kept within 100
     of the mean (i.e. all data).

     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.  There is no surface bin.

     DERIVE uses 1 db averaged pressure, temperature, and conductivity to
     compute salinity, theta, sigma-theta, and dynamic height.

     TRANS converts the data file from binary to ASCII format.

     Program CNV_EPS1 applies post-cruise temperature corrections and
     conductivity calibration coefficients, as well as any offset to salinity,
     recomputes the derived variables in DERIVE, and converts the ASCII data
     files to netCDF format.  CNV_EPS1 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_EPS1
     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.

     Primary data were interpolated between 21-42 dbars for station 7.  
     Secondary data weren't used because the cond sensor was bad and not 
     swapped out until station 13.  

     Several deep bottles were flagged bad: stations 2, 8, 10, 24, and 26 
     sample 102; station 12 sample 101, and station 25 sample 103.

     Final CTD and bottle files were moved to /home/plover/insitu2/DATA/hayes
     /gp605/ctd/ and /bot and included in the MySQL data management tables on
     April 12, 2006.
