

Number 

 Comparisons 



Average 

 Difference, °C 



Standard 

 Deviation, °C 



GULF OF ALASKA 



44 



-0.05 



0.21 



SUDS I 



7 



0.06 



0.19 



CAPER 



22 



-0.33 



1.33 



RAPLOC/DEEPTOW 



17 



0.06 



0.13 



Table 18. Comparison of surface temperatures measured by the XBT and STD/SV. 



COMPARISON WITH THERMISTOR CHAIN 



During the SUDS I experiments, with the thermistor chain vertical in the water 

 (zero tow speed), six XBT profiles were obtained between 0650 and 0726 LST, 23 February 

 1972. On 12 February 1972 at 0428 LST, one XBT profile was made under similar circum- 

 stances. Comparisons of these measurements are contained in table 19. Recall that the 

 thermistor chain measures temperature at 44 depths spaced 5.6 m apart from the surface to 

 242 m every 10 s, and that the 460-m XBT profiles take 88 s to complete. For the measure- 

 ments made on 23 February, the thermistor chain profile is the scan that started at the same 

 time the XBT probe was released. Thus the surface temperatures are measured simultan- 

 eously. The thermistor chain measurements used to compare with XBT 81L are the average 

 of the nine 10-s scans made while the XBT probe was recording its 88-s profile. The 

 standard deviation of the nine thermistor chain measurements made on 12 February was 

 O.OTC. All of these differences lie within the XBT system accuracy of ±0.24°C. 



XBT 



Time 





Temperature 



°C 



Number 



Day /Mo 



Hour 



XBT 



Chain 



Difference 



273L 



23 Feb 



0650 



15.33 



15.42 



-0.09 



274L 





0700 



15.33 



15.42 



-0.09 



275L 





0708 



15.44 



15.42 



0.02 



276L 





0714 



15.49 



15.37 



0.12 



277L 





0720 



15.33 



15.40 



-0.07 



278L 





0726 



15.23 



15.40 



-0.17 



81L 



12 Feb 



0428 



14.67 



14.57 



0.10 



Table 19. Comparison of surface temperatures measured by the XBT and 

 thermistor chain systems. 



In addition to the above measurements the LEE, towing the thermistor chain at 

 3 knots, made continuous thermistor chain measurements during the SUDS I propagation 

 loss runs. During these runs, 153 XBT profiles also were obtained. These measurements 

 provide a set of comparative simultaneous surface temperature measurements that were 

 made underway at 3 knots. Figure 1 2 contains ogives of the positive and negative differ- 

 ences between the XBT and thermistor chain measurements. The average difference was 

 0.04°C, with a standard deviation of 0. 1 3°C. Of the total number of differences, 63.4% 



37 



