COMPARISON WITH BUCKET THERMOMETER 



During the CAPER and RAPLOC/DEEPTOW experiments, bucket thermometer 

 surface temperatures were obtained at the same time many of the XBT profiles were 

 made. During the CAPER experiment, 151 bucket temperatures were obtained by the DE 

 STEIGUER and 138 bucket temperatures were obtained by the MOANA WAVE. Since the 

 DE STEIGUER XBT surface temperatures, corrected for system error, were used to estab- 

 lish the bucket thermometer system error (see above), the bucket temperatures are not 

 independent of the XBT temperatures and cannot be used to determine the surface tempera- 

 ture measurement accuracy of the XBT system. However, the system error for the MOANA 

 WAVE bucket thermometer was estabhshed from the CTD/SV measurements and is 

 independent of the XBT temperatures. 



Figure 22 is a plot of the MOANA WAVE differences in temperature between the 

 XBT and bucket temperature versus the consecutive XBT number. Differences shown by 

 the symbol (x) are the difference between the CTD/SV and bucket temperatures. The 

 XBT differences for the first 45 profiles were comparable. However, for the XBT profiles 

 made subsequent to XBT 45, large and erratic differences between the XBT and bucket 

 temperatures were observed. From XBT 46 to 80, all but three of the XBT surface temper- 

 atures were less than the bucket temperatures, and XBT 56 measured a surface temperature 

 2.84°C lower than the bucket thermometer. For XBT 81 to 96, the XBT measured surface 

 temperatures higher than the bucket thermometer. The surface temperature for XBT 82 

 was 2.22°C higher than the bucket temperature. From XBT 97 to 177, the last to be made 

 by the MOANA WAVE, the XBT again measured surface temperatures lower than the 

 bucket thermometer. Also shown in figure 22 are the differences between the CTD/SV 

 surface temperature measurements and the bucket temperatures. The average difference for 

 20 comparisons was -0.02°C, with a standard deviation of 0.09°C.* From these compari- 

 sons, it is concluded that the MOANA WAVE XBT system began to malfunction starting 

 with XBT 48. Pertinent statistics are summarized in table 22. 



The observer aboard the MOANA WAVE, by comparing bucket temperatures with 

 the XBT surface temperatures, recognized that the XBT system was malfunctioning, and 

 after the completion of XBT 72 attempted to correct the malfunction by recalibrating the 

 system. XBT 77 was the first visually acceptable XBT profile made after recalibration. 

 Although recalibration brought about an improvement, the XBT 77 surface temperature 

 was still 0.92°C lower than the bucket temperature. After completing XBT 164, the 

 observer again recalibrated the system. The next XBT profile made after recalibration 

 measured a surface temperature 0.40°C higher than the bucket thermometer, and the one 

 following that measured a surface temperature 0.8 1°C lower than the bucket thermometer. 

 Thus the malfunction was not corrected by a recalibration of the system. 



To check whether the large surface temperature differences observed for the 

 MOANA wave's XBT profiles were linear shifts in the temperature scale, the 400-m 

 temperatures were plotted for the MOANA WAVE XBT profiles. These data are plotted in 



*Since the bucket thermometer system error was determined by using the CTD/SV surface temperatures, 

 the two measurements are forced to agree. However, the XBT system error is only 0.12 C (see above), 

 which is small compared to the differences between XBT and bucket temperatures. Some readers may 

 note that 18 CTD/SV surface temperatures were used to establish the XBT system error (see above), 

 and that 20 comparisons are shown in figure 22. In establishing the XBT system error, two of the CTD/SV 

 measurements were not considered quasisimultaneous with the XBT measurements and were not used. 



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