NBP09-01 Cruise Report - British Oceanographic Data Centre

and dissolved oxygen decreasing with depth. The maximum temperatures and salinities occurred near thebottom in this layer. And small steps occasionally occurred in its upper portion.The CTD operations were carried out by Robin Robertson, Katie Leonard, Chris Little, and Ken Mankoffwith the CTD operated by RPSC personnel George Aukon and Greg Watson. Thanks are due to RPSCmarine technicians Mike Lewis, Robert Zimmerman, Jullie Jackson, and Amy Schaub for their outstandingdeployment of the CTD and rosette and their prompt mechanical repairs. We also appreciate the excellentwinch operations of a Ben Aaron, Ric Tamayo, and Louie Andrada. Raul Guerrero assisted with setting upboth the sensors and processing.2.2 LADCPA 300kHz RDI Lowered Acoustic Doppler Current Profiler (LADCP) was attached on the CTD rosette framefacing down. It was deployed on each CTD cast to provide a profile of the horizontal velocities with depth.Only a single LADCP head (SN 754) was used. Typically, the LADCP battery was charged every 3 casts,with the charging requiring between 20 min and an hour. The charging time needed depends on the chargeremaining in the battery. It is possible that more time might be requred if the battery voltage was lower.The LADCP operated well, without any problems due to broken beams. There are two CTD casts withoutLACDP profiles. On cast 1, the LADCP cover was not removed, with the result that there was no validdata. On cast 116, the instrument was not properly started due to operator error. Local times instead ofGMT times were saved for LADCP profiles 2-36. The times both in the files and on the printed graphs in theCTD Log book are incorrect. The LADCP computer was shifted to GMT after cast 36 and the processingscripts modified to correct the time for incorporation of CTD and shipboard ADCP (SADCP) data. Therewere no problems with lack of scatterers in deep water, even on cast 160, which reached 4497 dbar. It shouldbe noted that LADCP profile 2 goes with CTD cast 2b, not the non-existent CTD 2.LADCP data was processed in Matlab using Andreas’ Thurnherr’s version IX.5 of the processing code,process cast. Note the plots indicate version IX4, but the processing software says IX5. The processingincorporated processed CTD and SADCP data to provide navigation data and constrain the LADCP velocityprofile, reducing errors. The SADCP was an RDI 150 kHz narrowband instrument. The maximum range ofthis instrument is 300 m, but valid data typically ceased between 250-280 m. Profile plots of the processedvelocities for each LADCP profile are included in the CTD Log book. Only six LADCP profiles experiencedprocessing errors. Three of these are casts 1, 2, and 116 as noted above. A shear solution was determinedfor profile 2. Three profiles showed pressure spikes in scans. These were casts 150, 151, and 153, which had20, 20, and 22 pressure spikes in 2 scans, respectively. Their processing reports are included in the CTD Logbook.During the yo-yo casts (58-81), the LADCP was charged for 15-20 minutes after each cast, after cast 66.Monitoring of the LADCP battery voltage showed this to be sufficient to maintain the batter voltage of 50V. Before cast 66 of the yo-yo, the LADCP was charged only once, after cast 60. Profiles 58, 61, and 64 eachhave multiple casts within the original raw data file, with 3 casts each in 58 and 61 and 2 casts in 64. AMatlab script, split yoyo, was written to split the original raw files into separate raw files for each of the casts.This script is specific for these casts, although it could be generalized. When using split yoyo, it is necessaryto run it twice. The first time, the data is plotted and the user must identify the scan number for separationof the casts. It is relatively easy to identify scans when the LADCP is aboard the ship by the relativelyconstant zero velocity values. Any scan number within that period is valid for the split. This has been donefor these three cases with multiple profiles and the scan numbers hardcoded into the script split yoyo. Inthe future, if a general script is desired, the hardcoding of these scan numbers and the file names need to bemodified. Note the three original raw files were renamed with an underline between the first and last castnumbers, ie. the original LADCP profile 58 raw file with three casts is named 058 60dn000.000, as opposedto its original name 058dn000.000. The new file of that name has only the raw data corresponding to cast 58in it. This was done in order to allow processing of this data without further modification of the processingsoftware.NBP09-01 Cruise Report (p. 10 of 83) Revised February 27, 2009