GP4-04-KA NOAA Ship KA'IMIMOANA Kwajalein, Marshall Is. - Honolulu, HI July 19 - August 17, 2004 Chief Scientist: Kristy McTaggart Survey Department: ST Shawn Gendron CTD Personnel: ST Shawn Gendron, Nicole Schuetz Final Processing: K. McTaggart ACQUISITION: Fifty CTD profiles were collected during this cruise. Twenty-two profiles were collected from 8N to 8S along 165E. The ship's trackline was ammended to go from 8S 165E to 0 172E, pick up a drifting buoy (CTD 0231 after recovery), and go back to 8S 180 to resume the second line. Twenty-seven profiles were collected from 8S to 8N 180, and along the ship's trackline to 12N. The majority of casts were to 1000m. Seven casts were deep (>3700m). PMC's Sea-Bird 9plus CTD s/n 09P13807-0439 measuring pressure (s/n 59788), temperature sensors s/n 1710 (TAO) and s/n 4211 (PMC) and conduc- tivity sensors s/n 1697 (PMC) and s/n 1537 (TAO) were used for all casts. The configuration file used for all casts was 19Jul04.CON. The CTD was mounted in the TAO spare custom 24-bottle frame with TAO SBE carousel pylon s/n 407. The CTD data stream was passed through TAO 11plus deck unit s/n 376 with factory settings. Digitized data were sent to a new Dell personal computer using Windows XP OS equipped with Sea-Bird's SEASOFT Windows acquisition software. 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 a Sony thumb drive and DVD. DVDs were returned to PMEL for post-cruise processing. SALINITIES: No duplicate samples were taken this cruise. Salinity analysis was performed using Guildline Autosal 8400B salinometer s/n 61.667, Ocean Scientific ACI2000, and IAPSO standard seawater batch #P143 dated February 2003. The bath temp- erature was set to 24 degrees Celsius. This season, only 8 samples will be collected per cast instead of 12, and no samples will be collected from the half-degree stations between 3N-3S. Raw data were archived along with CTD data on DVD. 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. POST-CRUISE CONDUCTIVITY CALIBRATIONS: GP404s.cal of secondary sensor data (te 4211, co 1537) was created at PMEL and used to calibrate all stations 1-50. Final pressure and temperature calibrations were pre-cruise. A viscous heating correction of -0.0006 C was applied to temperature sensor s/n 4211 but no historical data for a drift correction are available. For conductivity 1537, stations 1-50, CALCOS0 was used to determine the fit: number of points used 279 total number of points 303 % of points used in fit 92.08 fit standard deviation 0.003988 fit bias -0.0047261083 min fit slope 1.0000978 max fit slope 1.0000978 Slope and bias correction values were applied to CTD burst data and converted directly into netCDF format 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 sensor pairs. 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 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. 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_EPS2 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_EPS2 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 15 db. Because the SBE module LOOPEDIT does not handle package slowdowns and reversals well in the thermocline where gradients are large, CNV_EPS2 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. Seven bottles were flagged bad: station 0111 samples 109, 110, 113; station 0181 and 0271 sample 101; and station 0311 samples 104 and 109. Final CTD and bottle files were moved to /home/plover/insitu2/DATA/hayes /gp404/ctd/ and /bot and included in the MySQL data management tables on September 16, 2004.