9.2. Use of Two Bathythermographs Simultaneously 



The use of two Bathythermographs simultaneously rather than one Bathyther- 

 mograph and bucket thermometer will give invaluable information in regard to ocean 

 variability versus random error. 



Employment of the coefficient of correlation as outlined above, but using the 

 values recorded by the two Bathythermographs, (not only at the zero depth value 

 but at many depths) will provide a measure as to the extent of ocean variability 

 and random error of the instruments. 



High correlation coefficients between the two Bathythermographs will indicate 

 that the variations observed are really in the ocean. Low correlation coefficients will 

 reveal that these variations are random errors of the instrument. 



The two Bathythermographs should be on the same cable and as close together 

 as possible. Also they should be reliable instruments, and matched, to the extent 

 that the random errors should be about equal in magnitude. 



9.3. Other Techniques to Correct Bathythermograph Sets 



In lieu of employing an independent temperature measurement to correct the 

 Bathythermograph to read absolute temperature values, other techniques present 

 good possibilities. These are discussed in categories below. 



9.3.1. Correction of Bathythermograms through Heat Content Studies 



Theoretical studies can be undertaken assuming that no significant change in 

 the heat content of the water will exist over this time of study. This condition is 

 especially true where the ship which took the Bathythermograms was in a relatively 

 fixed position during the time the Bathythermograms were taken. Any apparent 

 large change in heat content represented by the temperature measurements of the 

 Bathythermograph could therefore be considered to be produced by an error in the 

 Bathythermogram values. Furthermore, this error can be considered a translation 

 of the slide, or in other words a variation in the set of the Bathythermograph. 



By integrating each Bathythermogram with respect to temperature an arbi- 

 trary heat content value can be established. This is in accordance with the following 

 equations : 



9z,-z, = fll A PCp(T,^-T2^)dZ (1) 



where Zi and Zo are the depths from which the integration takes place. 

 Where A, -p, C? (area, average density, and specific heat) are constant, as would 

 be the case in comparing Bathythermograph traces representing nearly constant 

 conditions, the equation reduces to the following: 



^ = K . /: (T„ - T.JaZ (2) 



where the integration takes place from the surface to the bottom of the trace. 

 The Bathythermogram trace represents temperature as a function of depth, 



i-e.: Tg = f (Z) (3) 



29 



