                    CTD CALIBRATION: CRUISE ARANDA 7/1990                  
                                                                           
CTD  profiles  were corrected using calibration coefficients  derived  from
cruise Aranda 7/1990. A summary of the results is presented herein.        
                                                                           
                                                                           
Temperature                                                                
CTD temperature was corrected by applying the coefficients derived from the
laboratory calibration of 21 June 1990:                                    
                                                                           
  T(cor) = T(ctd) + dT                                                     
                                                                           
where dT = c + b*T(ctd) + a*T(ctd)*T(ctd)                                  
and    a = -0.32614x10-4                                                   
       b = -0.613104x10-3                                                  
       c =  0.925468x10-3                                                  
                                                                           
                                                                           
Pressure                                                                   
CTD  pressure was corrected by applying the coefficients derived  from  the
laboratory calibration of 21 June 1990:                                    
                                                                           
  P(cor) = P(ctd) + dP                                                     
                                                                           
where dP = a*T(cor) + b*P(ctd) + c                                         
and    a = 0.10425532                                                      
       b = 0.36670552x10-2                                                 
       c = 0.541245580                                                     
                                                                           
                                                                           
Conductivity Ratio                                                         
CTD  conductivity was corrected by converting water sample salinity  to  in
situ  conductivity  (from  the UNESCO algorithm) and comparing  it  to  CTD
conductivity values. The water sample salinity was measured using Guildline
bench  salinometer.  A  least  squares  regression  was  performed  on  the
corrected  data to derive the calibration coefficients a,  b and c and  the
corrected conductivity ration is:                                          
                                                                           
 CR(cor) = CR(ctd) x CR                                                    
                                                                           
where CR = a*T(cor) + b*P(cor) + c                                         
and    a =  0.102667575x10-3                                               
       b = -0.238495919x10-7                                               
       c =  0.993272182                                                    
                                                                           
The derived P,  T and CR calibration coefficients were used to correct  the
CTD profiles of the cruise.                                                
                                                                           
                                                                           
Results                                                                    
Station details are shown in Table 1. The root mean square (rms) difference
between the corrected CTD salinity and water sample salinity was 0.004  for
6  observations.  This was found to be acceptable,  in view of  the  errors
inherent in the CTD and bench salinometer.  Only stations 1 and 2 were used
in determining the calibration coefficients.                               
                                                                           
In  correcting the CTD profiles at stations 1,  2 and 3,  odd values of  CR
were deleted from the top 100 m. The profile of station 3 was very noisy in
the first 400 m and, consequently,  these were deleted.  The corrected data
are in ARAN790S1.DAT, ARAN790S2.DAT and ARAN790S3.DAT,  now archived on the
vax in directory CTD.DATA.AO.CTDFOR.                                       
                                                                           
                                                                           
Jackie Cooper                                                              
20 Sept. 1990                                                              
                                                                           
                                                                           
Table 1: Station details for cruise 7/1990                                 
Station      Latitude      Longitude      Date        Time      Depth      
1           65 08.96 N     30 50.74 W     11 July     04.20     1533m      
2           64 46.04 N     30 33.16 W     11 July     14.57     2192m      
3           64 17.35 N     33 42.39 W     13 July     14.33     1966m      
