To determine whether the TCS decreased or increased the error for a 

 large sample of data, the means and standard deviations of the differences 

 between corrected and uncorrected values of all observations from the six 

 cruises were computed. The mean difference was .56°F for the uncorrected 

 data and ,kk^ for corrected data. The standard deviation was .SU^F for 

 the uncorrected data and ,73°F for the corrected data. Although the TCS 

 appears to improve the accuracy of BT data, the improvement is soaU.. 



In general, Winterfeld (reference k) and Saur (reference 5) concluded 

 that a mercury bucket thermometer was more reliable and more accurate than 

 an injection thermometer. However, Winterfeld notes that the air-sea tem- 

 perature difference in DELTA II data affects bucket temperatures but does 

 not affect reversing thermometer temperatures. 



To determine whether air-sea temperature difference affects bucket 

 temperature, the data from the DELTA cruises and the ECHO V cruise were 

 plotted. The graphs were constructed by plotting reversing thermometer 

 surface temperature minus bucket temperature against the reversing thermo- 

 meter value minus air temperature (figures 2, 3, h, 6, and 7). Figures 5 

 and 8 use a 3-foot temperature probe reference instead of the bucket tem- 

 perature . 



In addition, correlation coefficients were computed (table 6). The 

 correlation between air-sea temperature differences and bucket temperature 

 readings is high. The correlation is low when a probe 3 feet below the 

 surface is used as a reference temperature. Winterfeld concludes that 

 bucket values are affected by air temperature. The bucket thermometer 

 probably records the true sea surface temperature, and a temperature gra- 

 dient related to the air- sea temperature difference exists in the upper- 

 most foot of water. 



TABLE i 



CORRELATION COEFFICIEMPS - REVERSING 



THERMOMETER SURFACE TEMPERATUEIB MINUS BUCKET THERMOMETER TEMPEEWTURE 



VERSUS REVERSING THERMOMETER SURFACE TEMPERATURE MINUS AIR TEMPERATURE 



Cruise 



Correlation 



DELTA I 



.57 



DELTA II 



.7U 



DET,TA III 



.72 



DET.TA IV (3-foot probe) 



.10 



DELTA V 



.80 



ECHO V 



,66 



ECHO V (3-foot probe) 



.16 



It may be concluded that reference temperatures for BT bias correc- 

 tions must be obtained at an independent check point located at some 

 depth rather than at the surface. 



16 



