All Visually Acceptable Profiles Reaching 400 m anSTlaving 

 Independent Surface Temperature Measurements 



The previous analysis suggested that temperatures and vertical temperature gradients 

 in the 200-to^OO-m layer were systematically biased when compared to average hydrocast 

 and STD/SV measurements. This analysis considered all XBT profiles made in water masses 

 where enough 200-, 300-, and 400-m hydrocast and STD/SV measurements were made to 

 establish an average temperature and its variance. Not all of these profiles reached 400 m, 

 which resulted in a different number of comparisons at each depth. This question might 

 now be asked; Are the results of the preceding analysis influenced by having different 

 numbers of comparisons at each depth? 



A second question that arises: Are the temperatures and vertical temperature 

 gradients also biased in the surface-to-200-m layer? 



Insight into these questions may be gained by considering the subset of all profiles 

 that reached 400 m and also had an independent surface temperature measurement. This 

 subset consists of 528 profiles. The results of the analysis of this subset are summarized in 

 appendix C and tables 33, 34, and 35. The format used is the same as for the preceding 

 analysis. 



Table 33 , summarizing the results for the set of all visually acceptable Gulf of Alaska 

 water mass 2 and transition water mass, as well as the CAPER water mass 2 profiles, 

 supports the following observations: 



a. At 200 , 300 , and 400 m, the results are similar to the results presented 

 in table 28. 



b. The XBT profiles measure a surface temperature that, on the average, 

 is less than the independently measured temperature. 



c. The surface-to-200-m temperature gradient, on the average, is biased 

 positively with respect to the average hydrocast and STD/SV temper- 

 ature measurements. 



Thus, for the data set consisting of all visually acceptable profiles, the answer to the first 

 question is no, and the answer to the second question is yes. In addition, on the average, 

 the XBT profiles measured vertical temperature gradients from the surface to 400 m that 

 were larger than those measured by the hydrocast and STD/SV systems. These, then, are 

 the expected results if no procedures are used to detect malfunctioning systems. 



It was shown previously that two of the XBT systems malfunctioned. Of the 

 528 visually acceptable profiles, 177 (33.5%) were made with the systems malfunctioning, 

 and 351 (66.5%) were made with the systems not malfunctioning. The analysis of the 

 351 set I profiles is summarized in appendix C and table 34. An inspection of these data 

 shows that: 



a. At 200, 300, and 400 m, the results are similar to those presented in 

 table 29 for the Gulf of Alaska and CAPER water mass 2 data sets, 

 with minor differences associated with the other three data sets. 



b. At the surface, the XBT system now measured a temperature higher 

 than the independently measured temperature for four of the five data 

 sets. For the Gulf of Alaska water mass 2 data set, the average surface 

 difference was still negative. 



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