GP6-06-RB NOAA Ship RONALD H. BROWN Valparaiso, Chile - Panama October 31 - December 3, 2006 Chief Scientist: Steve Kunze Survey Department: CST Jonathan Shannahoff CTD Personnel: CST Jonathan Shannahoff Final Processing: Kristy McTaggart ACQUISITION: Thirty-five CTD profiles were collected at 35 stations during this cruise. Seventeen profiles were collected from 8S to 8N along 95W; 18 profiles were collected from 8N to 8S along 110W. The majority of casts were to 1000m, and 5 casts were deep (3000m). PMEL's Sea-Bird 9plus CTD s/n 315 (pressure s/n 53960) was used for all casts during this cruise, along with primary temp sensor s/n 4569 and primary cond sensor s/n 354, and secondary temp sensor s/n 4193 and secondary cond sensors s/n 3157. The CTD was mounted in PMEL/CFC bad weather 24-bottle frame with CFC 4-liter niskin bottles and TAO SBE carousel pylon s/n 53. 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 5.37d. 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 #P146. 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: GP606S.CAL of secondary sensor data (te 4193, co 3157) was created and used to calibrate stations 1-35. Final pressure and temperature calibrations were pre-cruise. A viscous heating correction of -0.0006 C applied to temperature sensor s/n 4193. There is no historical data for this fairly new sensor. The best conductivity calibration results were from an overall fit determined by CALCOS0: number of points used 251 total number of points 272 % of points used in fit 92.28 fit standard deviation 0.002685 fit bias -0.0038465181 min fit slope 1.0001905 max fit slope 1.0001905 Slope and bias correction values were applied to CTD burst data using a local version of CALMSTR that also applies a -0.005 bias to salinity. 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_EPS2 that also applied a -0.005 bias to salinity. PROCESSING: All casts were re-processed by KEM post-cruise for the proper format. 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_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 10 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. Final CTD and bottle files were moved to /home/plover/insitu2/DATA/hayes /gp606/ctd/ and /bot and included in the MySQL data management tables on January 9, 2007.