At11-17 ctd notes



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#15901

AT11-17 ctd notes

James R. Postel


General set-up of the ctd

The R/V Atlantis ctd package consisted of a Seabird 911 plus with dual temperature and conductivity sensors with pumped flow, SBE43 dissolved oxygen sensor, Wetlab ECO-AFL/FL fluorometer, Wetlab CStar transmissometer, Biospherical PAR/Irradiance sensor, an altimeter, and a surface PAR sensor input. In addition, there was an OBS turbidity sensor that never seemed to generate any good data stream. Eventually, at cast 101, the package failed to initialize upon start-up, and all fish cable connections were taken apart and put back together to determine which sensor had failed. It was the OBS sensor, which was then removed from the package. The package was assembled and the cruise configuration file (at1117.con) was copied from a previous cruise and modified to include the PAR and surface PAR sensors by the ship's Shipboard Scientific Support Group technicians (David Sims and Chris Griner). After a few days I got copies of the latest calibration sheets for the sensors that were available on board (except for the surface PAR sensor) and compared them with the configuration file coefficients and found two changes that needed to be made. The calibration constant for the Biospherical PAR sensor had been entered as 2.00e+10 instead of 2.00e+09. I changed it in the at1117.con file and in all the casts we had done to date, and renamed the default file at1117a.con. Later I discovered that one of the Digiquartz pressure coefficients (D1) had been entered incorrectly (3.994470e-02 instead of 3.944700e-02). The bad pressure coefficient is still in the .CON files for casts ctd001-ctd039. I made the change at cast ctd040, and the corrected file (at1117b.CON) was used for data collected from that point until the end of the cruise. I did not compare pressure calculations for a file with bad versus good coefficients and just used the existing cast .con files for copying into the various directories on the Gateway computer used for shipboard processing. However, I copied the 'at1117b.con' file into the 'current.con' file in the processing directory before I started doing the script processing. On 25 Sep Dave Sims found a conversion factor for the surface PAR sensor (9.97845e+16), and it was incorporated into the file at1117c.con, which was used for casts after ctd175. It should be included in the next round of processing to generate surface PAR numbers (units = ??).


The set-up of the sensors for the cruise was:

frequency 1 primary temperature (T0) SBE s/n 2446 calibrated 11 May 2004

frequency 2 primary conductivity (C0) SBE s/n 2148 calibrated 11 May 2004

frequency 3 pressure (Digiquartz with TC) s/n 58939 calibrated 20 Apr 2001

frequency 4 secondary temperature (T1) SBE s/n 2265 calibrated 11 May 2004

frequency 5 secondary conductivity (C1) SBE s/n 2077 calibrated 16 Jul 2004


A/D voltage 0 Wetlab ECO-AFL/FL fluorometer s/n 008 calibrated 21 September 2001??

A/D voltage 1 not used

A/D voltage 2 Biospherical PAR/Irradiance sensor s/n 4617 calibrated (unknown)

A/D voltage 3 Wetlab CStar transmissometer, 25cm path length, s/n CST-536DR, calibrated 30 Apr 2002

A/D voltage 4 SBE 43 Oxygen sensor, s/n 0712 calibrated 6 July 2004

A/D voltage 5 not used

A/D voltage 6 altimeter s/n (unknown) calibrated (unknown)--but it seemed to work very well

A/D voltage 7 Seapoint Turbidity OBS sensor s/n (unknown) calibrated (unknown)--never gave good data


SPAR voltage 0 unavailable

SPAR voltage 1 Surface irradiance model unknown, s/n (unknown) calibrated (unknown)



Onboard Data Processing:

I was unsure how to modify the scripts to accommodate the different order of the sensors for this cruise versus the R/V Wecoma set-up. Thus, the variable Fls always calculated to zero since it was not associated with voltage zero in the script file. For the Atlantis, voltage 0 was the fluorometer voltage, so that voltage will have to be used in the calculation of in vivo fluorescence (i.e. chlorophyll) in the next round of processing. (More on that later.)
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