*** Documentation for STD data collected on RRS Discovery Cruise 69 (Jan  -                                                         
Mar  1975)  by  the Department of Oceanography,  University  of  Liverpool,                                                         
Liverpool, U.K., under the direction of P. Hughes ***                                                                               
                                                                                                                                    
The  instrument  used  was  the  University  of  Liverpool  Bissett  Berman                                                         
Salinity-Temperature-Depth  system type 9006,  with a Rosette water sampler                                                         
attached to the wire above it.  The data output from each STD lowering  and                                                         
raising  was  automatically  recorded in digital and  analogue  form.  Data                                                         
storage was effected on paper tape and separately on disk on the ship's IBM                                                         
1800  computer.  There were some troublesome faults on the salinity  sensor                                                         
which produced occasional loss of signal when hauling in.  The intermittent                                                         
nature of the malfunction made it difficult to locate,  but the problem was                                                         
eventually  resolved  by changing the interconnecting harness  between  the                                                         
mixer and sensor units and by making good a suspect connection on a circuit                                                         
board in the salinity unit.  Despite these difficulties STD casts were made                                                         
successfully  at all the proposed positions.  An IOS water sampling  bottle                                                         
with  associated reversing thermometers was located as near to the probe as                                                         
possible  on  each cast for calibration purposes.  Consistent  calibrations                                                         
with   the  makers  specified  tolerances  were  determined.  The   rosette                                                         
multisampler  was  initially  used for salinity calibrations  and  to  take                                                         
samples  at  standard  depths  for chemical  determinations.  Its  use  was                                                         
eventually  discontinued  in  favour of separate bottle  casts  because  it                                                         
suffered from intermittent failures and bottle leakage.                                                                             
                                                                                                                                    
Stations  were identified by their 4 digit Discovery station  number.  Time                                                         
series  measurements were taken at 2 stations.  These were at station 8765,                                                         
where  STD dips were made to 300m every hour between 0630h and 1830h on  24                                                         
Feb  1975,  and station 8772,  where STD dips were made every hour to  300m                                                         
between  0630h  and  1830h  on 26 Feb 1975.  For  stations  8765  and  8772                                                         
individual  dips  are identified by the 4 digit Discovery  station  number,                                                         
followed by the sequence number of the dip (from 01 to 13).                                                                         
                                                                                                                                    
The  absolute accuracies of the temperature and salinity measurements  were                                                         
checked  by  comparison  with  a series  of  temperature  measurements  and                                                         
salinity  samples  obtained with reversing thermometers and  water  bottles                                                         
over  the  course  of  the cruise.  The  comparisons  using  the  reversing                                                         
thermometers  showed that the temperature sensor was operating  within  the                                                         
manufacturer's specified tolerances and no corrections were necessary.  For                                                         
the  salinity  0.03ppt was added to all the observations taken  during  the                                                         
first  leg of the cruise (21 Jan - 18 Feb 1975) and 0.016ppt on the  second                                                         
leg  (18  Feb - 18 Mar 1975).  After calibration against the  water  bottle                                                         
observations  the STD data were despiked,  smoothed and interpolated to  1m                                                         
depth intervals.                                                                                                                    
                                                                                                                                    
References:                                                                                                                         
                                                                                                                                    
RRSDiscovery  Cruise 69,  21 January - 18 March 1975 Upwelling  off  north-                                                         
   west Africa.  Institute of Oceanographic Sciences Cruise Report No.  51.                                                         
   1977.                                                                                                                            
                                                                                                                                    
Brockmann, C., Hughes, P. and Tomczak, M. (1977).  Data report on currents,                                                         
   winds  and  stratification in the North-west  African  upwelling  region                                                         
   during early 1975. Berichte aus dem Institute fur Meereskunde No. 32.                                                            
