***  Documentation  for the CTD data collected on  RRS  Challenger  Cruise                                                          
19/87  (29  Sep  1987  - 13 Oct 1987) by the  School  of  Ocean  Sciences,                                                          
University College of North Wales, Menai Bridge, U.K., under the direction                                                          
of A.E. Hill  ***                                                                                                                   
                                                                                                                                    
DATA COLLECTION                                                                                                                     
The  instrument  used was a Neil Brown Instruments System  Mark  III  CTD.                                                          
Observed  parameters  were  pressure, temperature  and  conductivity.  The                                                          
instrument was lowered as slowly as possible,  at about 1 m/s.  In general                                                          
the  CTD was lowered to within 5-10 metres of the seabed,  except on  some                                                          
slope stations when a rising slope prevented this. The data were logged on                                                          
a BBC microcomputer.                                                                                                                
                                                                                                                                    
CALIBRATION                                                                                                                         
There were some rogue calibration data points.  On examination these  were                                                          
found  to have been collected in areas of strong temperature  or  salinity                                                          
gradients and have been omitted from the statistics.                                                                                
                                                                                                                                    
Temperature:                                                                                                                        
The temperature calibration readings made using mercury-in-glass reversing                                                          
thermometers  gave  somewhat  variable readings, in  part  due  to  strong                                                          
temperature  gradients in the areas sampled. Hence these were not used  to                                                          
calibrate  the  CTD.  It  was felt that the Neil  Brown  sensor  was  more                                                          
accurate  and  no temperature correction was made.   The  results  of  the                                                          
temperature  calibrations on two associated cruises RRS  Challenger  23/87                                                          
and RRS Challenger 24/88 confirmed that this was the best solution.                                                                 
                                                                                                                                    
Salinity:                                                                                                                           
Water  samples  for salinity determinations were taken on most  casts;  on                                                          
some casts, particularly the deeper ones, more than one calibration sample                                                          
was taken.                                                                                                                          
                                                                                                                                    
     Mean salinity difference (Water sample - CTD)  =   0.0162                                                                      
     Standard Deviation                             =   0.0075                                                                      
     Variance                                       =   0.0000                                                                      
     No. of points                                  =   194                                                                         
                                                                                                                                    
     Salinity = CTD salinity + 0.0162 (PSU)                                                                                         
                                                                                                                                    
Pressure:                                                                                                                           
There was no pressure calibration for this cruise.                                                                                  
                                                                                                                                    
                                                                                                                                    
DATA PROCESSING                                                                                                                     
The  University's  mainframe computer was used for  processing  the  data,                                                          
using an in-house Pascal CTD package. The data were checked for  erroneous                                                          
readings and the up and downcasts were averaged.   The calibration details                                                          
were applied and the data were processed into 1m depth bins.                                                                        
                                                                                                                                    
Reference:                                                                                                                          
Mitchelson-Jacob,  E.G., Hill, A.E. and Simpson, J.H.  A report on the CTD                                                          
data  collected west of Scotland during the winter of 1987-88 as  part  of                                                          
the  Scottish  Coastal Current and Autumnal Circulation  Experiment  (ACE)                                                          
programmes.  School of Ocean Sciences, University College of North  Wales.                                                          
January 1989.                                                                                                                       
