*** Documentation for the CTD data collected on RV Ignat Pavlyuchenkov (Oct                                                         
- Nov 1991) by the School of Ocean Sciences,  University of Wales,  Bangor,                                                         
under the direction of E.D. Barton. ***                                                                                             
                                                                                                                                    
This  cruise  formed  part  of EU MAST  Project  0031  -  European  Coastal                                                         
Transition  Zone,  Islas  Canarias,  with partners from the  University  of                                                         
Wales,  Bangor,  UK,  Universidad de Las Palmas de  Gran  Canarias,  Spain,                                                         
Centro  Oceanografico  de  Canarias,  Spain and Centro Comune  di  Ricerca,                                                         
Ispra, Italy.                                                                                                                       
                                                                                                                                    
Throughout the cruise period most of the equipment performed well and  only                                                         
minor  problems occurred.  The only major difficulty was in relation to the                                                         
CTD  which  was  initially being used (known as  the  'Russian  CTD');  the                                                         
conductivity sensor of which was accidentally damaged. Thus, the entire CTD                                                         
system  was  replaced by the one taken aboard as part of the University  of                                                         
Wales,  Bangor/ Research Vessel Services (UWB/RVS).  The equipment  of  the                                                         
'Russian'  and  'UWB/ RVS' CTD systems was comparable.  Both included  Neil                                                         
Brown CTD Mark III units, fluorometer (Sea-Tech 57S and Chelsea Instruments                                                         
respectively),  25cm Sea-Tech transmissometer,  and a Rosette sampler of 24                                                         
bottles and 12 bottles.  Data in both cases were logged using EG&G software                                                         
running under MS-DOS and IBM type personal computers.                                                                               
                                                                                                                                    
In  order  to calibrate the different sensors of the two CTD  systems  used                                                         
through  the cruise,  water samples and temperature readings were routinely                                                         
taken during most of the CTD casts.                                                                                                 
                                                                                                                                    
To achieve the calibration of the conductivity sensors,  the water  samples                                                         
were analysed on the salinometer brought aboard as part of the equipment of                                                         
the Spanish Institute of Oceanography (IEO), and the difference between the                                                         
two sources of data (i.e.  the data measured by the CTD minus the data from                                                         
the  salinometer)  was calculated.  Similarly,  in order to  calibrate  the                                                         
temperature  sensors  the   difference   between   the   CTD  and  revering                                                         
thermometers was also estimated.  The calibration curves of both parameters                                                         
were then updated.                                                                                                                  
                                                                                                                                    
Following application of the calibration,  each profile of temperature  and                                                         
salinity  was iteratively displayed and corrected if necessary.  As a first                                                         
error inspection, artificial structures (i.e. isolated spikes) were removed                                                         
and linear interpolation used to correct the profiles.                                                                              
                                                                                                                                    
The Sea-Tech 57S fluorometer is a linear response instrument.  The  Chelsea                                                         
Instruments  Mark II Aquatracka is a logarithmic response instrument.  Data                                                         
derived  from  this instrument were comparatively noisy and  were  smoothed                                                         
with  a  7  point running average filter to remove the  larger  spikes  and                                                         
oscillations.  Samples  for  fluorometer calibration were  taken  at  known                                                         
depths  within  several CTD and fluorescence profiles,  using  the  Rosette                                                         
bottles.  Typical  sampling depths include deep  water,  the  chlorophyll-a                                                         
maximum and the surface mixed layer. The bottle samples were analysed using                                                         
a  Turner  bench  fluorometer and the concentration  of  chlorophyll-a  and                                                         
phaeopigments calculated.                                                                                                           
                                                                                                                                    
Sample  concentrations  of   chlorophyll-a   were   plotted  against  their                                                         
fluorescence voltage,  measured on the corresponding profiling fluorometer.                                                         
A linear regression analysis was performed on the Sea-Tech instrument data,                                                         
whilst  a  non-linear curve fitting program was employed to  establish  the                                                         
Chelsea Instruments Aquatracka calibration.  These relationships were  then                                                         
used  to  convert  all  the fluorescence profiles to  profiles  of  pigment                                                         
concentration.                                                                                                                      
                                                                                                                                    
The  following equations were used to convert the fluorometer  voltages  to                                                         
predicted chlorophyll-a concentrations in mg/m**3:                                                                                  
                                                                                                                                    
Sea-Tech fluorometer:                                                                                                               
                                                                                                                                    
fluorescence voltage = (3.67 x chlorophyll concentration) + 0.24                                                                    
                                                                                                                                    
Chelsea Instruments Aquatracka fluorometer:                                                                                         
                                                                                                                                    
fluorescence voltage = 2log ((2.90 x chlorophyll concentration) + 1) + 0.66                                                         
                                                                                                                                    
References:                                                                                                                         
                                                                                                                                    
Velez-Munoz,   H.S.  October  1992.  Ignat  Pavlyuchenkov  Cruise   Report:                                                         
Hydrographic Field.  European Coastal Transition Zone Islas Canarias,  MAST                                                         
Project 0031. Report 0031-09                                                                                                        
                                                                                                                                    
Wild,  K.A.  May  1992.  Ignat Pavlyuchenkov  Cruise  Report:  General  and                                                         
Phytoplankton  Biomass.  European Coastal Transition Zone  Islas  Canarias,                                                         
MAST Project 0031. Report 0031-08                                                                                                   
