GP4-02-KA NOAA Ship Ka'imimoana Kwajalein, Marshall Islands - Honolulu, HI July 1-29, 2002 Chief Scientist: Mr. Andy Shepherd Survey Department: ST Jason Poe CTD Personnel: ST Jason Poe, Martin Guiles, Andy Shepherd Final Processing: K. McTaggart ACQUISITION: Fifty-one CTD profiles were collected during this cruise. Twenty-three profiles were collected along 165E from 8N to 8S. Twenty-eight profiles were collected 8S to 12N along 180 and the cruise track to Honolulu. The majority of casts were to 1000m; 6 were deep and 2 were to 500 m. 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 conductivity conductivity sensors (TAO s/n 1469, ship s/n 1536) were used for casts 1-3. Secondary temperature sensor s/n 1708 replaced s/n 2026 for casts 4-18. During cast 18, the entire package was lost owing to a break in the cable. A backup package was assembled including PMC's CTD s/n 405, temperature sensors 2109 and 1710, and conductivity sensors 1725 and 1467. This configuration was used for casts 19-29. PMC CTD s/n 439 replaced s/n 405 for casts 30-51. The CTD was mounted in a custom 24-bottle frame with Sea-Bird rosette sampler s/n 88 for casts 1-18, and s/n 54 for casts 24-29. Pylon 88 was having problems in earlier cruises and failed altogether on cast 29. There wasn't a third pylon on board. 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 for casts 1-23 only. The survey tech purposely stopped making VCR backups. 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 the CDs were returned to PMEL for post-cruise processing. SALINITIES: 12 samples were taken from casts 1-17 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 was assumed to be between 22-24 degrees Celsius. Raw data were archived on floppy disk. No processing was done on Survey's NT machine. The original floppy was NOT returned to PMEL in the data package. .DAT files were emailed to PMEL from Honolulu. 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: GP402S.CAL of secondary sensor data for casts 1-17 was created at PMEL using revised NT processing procedures. Primary TC pair (s/n 2027, 1469) were less noisy and used in the final processing. Final pressure and temperature calibrations were pre-cruise. A viscous heating correction of -0.0006 C and a historical drift correction of -0.0003 were applied to temperature sensor s/n 2027. Conductivity fit coefficients were determined using Matlab program CALCOS0. number of points used 183 total number of points 202 % of points used in fit 90.59 fit standard deviation 0.005834 fit bias -0.014590693 min fit slope 1.0006107 max fit slope 1.0006107 Slope and bias correction values were applied to CTD data and converted directly into netCDF format. It was determined by comparison of deep cast 0161 at 2S, 165E with historical profiles that an additional salinity offset of -0.0042 be applied to casts 1-18 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. Cast 0091 data need to be replayed from VCR tape at a later date. At this time, only data between 275-818 db were recoverable, and were not loaded into the database. Also, several casts are missing more than 10 db of data at the beginning of the profile. These data were extrapolated back to the surface within 20 dbar.** Casts 0101 and 0471 were despiked at depth. It was determined that an additional salinity offset be applied to all casts. Historical profiles at deep station sites were used to determine the offsets, -0.0042 for casts 1-18 and +0.0091 for casts 19-51. 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). CLB_SHIFT_EPS was used for this cruise to apply a salinity offset of -0.0042 after calibrations to casts 1-18 bottle files. Final CTD and bottle files were moved to /home/plover/insitu2/DATA/hayes /gp402/ctd/ and included in the MySQL data management tables on October 7, 2002. ** This was done on 12/23/02 by KEM.