biases are positive and 25 (49.0%) negative. Again, for this layer, more of the larger gradient 

 biases are positive. 



Table 39 lists the largest positive and negative temperature differences and the XBT 

 profile which measured these differences, and table 40 lists similar information for the 

 temperature gradient biases. The largest 200-, 300-, and 400-m positive temperature 

 differences were all measured, at anchor from the ORB, by XBT 55A during RAPLOC/ 

 DEEPTOW. The largest 200-m negative differences were measured by XBT 66A during 

 RAPLOC/DEEPTOW, and the largest 300- and 400-m negative differences were measured 

 by XBT 188L during SUDS I. The largest 200-300-m positive temperature gradient bias 

 was measured by XBT 81D taken during CAPER, and the largest positive 300-400-m 

 bias was measured by XBT 55A taken during RAPLOC/DEEPTOW. Note that XBT 55A 

 was made during RAPLOC/DEEPTOW from the ORB at anchor. The largest negative 

 gradient bias in the 200-300-m depth interval was measured during SUDS I by XBT 128D, 

 and the largest negative 300-400-m bias by XBT 134D also during SUDS I and by XBT 44B 

 during RAPLOC/DEEPTOW. Facsimiles of the XBT profiles listed in tables 39 and 40, as 

 well as facsimiles of the XBT profiles measuring the second largest positive and negative 

 differences at each depth, are included in appendix G. An inspection of these profiles 

 suggests that in the absence of other information, such as average hydrocast and STD/SV 

 temperature measurements, these profiles are all visually acceptable. There is little reason to 

 suspect that they contain errors as large as this analysis suggests. 



Depth, 



Largest Positive 



Largest 



Negative 



m 



XBT Number 



Difference, °C 



XBT Number 



Difference, °C 



200 

 300 

 400 



R/D 55A 

 R/D 55A 

 R/D55A 



2.01 

 2.33 

 3.02 



R/D 66A 

 SUDS 188L 

 SUDS 188L 



-0.73 

 -0.66 

 -0.37 



Table 39. Tabulation of largest positive and negative temperature differences. 



Depth, 



m 



Larges 



Positive 



Largest Negative 



XBT Number 



Bias, °C/1 00 m 



XBT Number 



Bias, °C/1 00 m 



2-300 

 3-400 



CAPER 81 D 

 R/D55A 



0.96 

 0.69 



SUDS 128D 

 SUDS 1 34D 

 R/D 44B 



-0.73 

 -0.33 

 -0.33 



Table 40. Tabulation of largest positive and negative temperature gradient biases. 



Of special interest is figure 37, which combines facsimiles of the RAPLOC/ 

 DEEPTOW XBT profiles 55A and 54A on a common XBT chart. XBT 55A is the profile, 

 listed in tables 39 and 40, with the largest positive 300-400-m positive gradient bias. In 

 contrast, XBT 54A, taken 1 hour before XBT 55A, satisfied the accuracy criteria at all three 

 depths. The differences for XBT 54A were 0. 1 TC at 200 m , -0.05°C at 300 m, and -0.1 0°C 

 at 400 m. Without the additional informadon provided by the hydrocast and STD/SV 



94 



