during DELTA II and III. During DELTA II injection temperatures averaged 

 .U3°F greater than reversing thermometer temperatures. Dviring DELTA III 

 injection temperatxires averaged .98°? less than reversing thermometer 

 temperatures. 



Ore possible source of injection thermometer error could be faulty 

 observition by the ship's engineer. During DELTA II and III the injection 

 thermoireter was read by an oceanographer and the engineer at approximately 

 the samt3 time. The mean differences between these simultaneous observa- 

 tions, .13° and .l8°F, are insignificant; however, large standard devia- 

 tions (.75 and .85) indicate considerable variation between observations. 

 Differences of this magnitude are understandable in view of the fact that 

 the injection temperature dial on the CHINCOTEAGUE is calibrated in 2°F 

 intervals and is inconveniently located among pipes about I8 inches below 

 the deck level. 



Winterfeld (reference k) concluded that the time-consuming and costly 

 process of computing a BT bias correction (TCS) is not warranted when 

 injection readings are used as reference temperatures. Unadjusted BT read- 

 ings are probably more accurate. Since July I963, NODC has not applied the 

 TCS factor to observations even if bucket reference temperatvires were avail- 

 able. Since NODC-processed BT observations are used extensively for research, 

 it was necessary to determine the effect of eliminating the TCS factor when 

 bucket temperatures are available. 



Reversing thermometer observations from DELTA and ECHO cruises were 

 used as absolute temperature values for comparison with simultaneously 

 recorded BT observations. Reversing thermometer observations for each 

 cruise were compared with sea surface temperatures read from the BT in the 

 field. Comparisons were also made between the reversing thermometer obser- 

 vations at the depth of the nansen bottle and the corrected and uncorrected 

 BT prints. 



Simultaneous observations for each cruise were divided into groups 

 of 25- or 50-meter depth intervals. The mean, standard deviation, and 

 confidence limits (t^s) of the differences were then computed (table 5). 

 The results give no answer as to the effect of the TCS. In many cases the 

 TCS adjustment increased the mean temperature error, even when bucket 

 thermometer values were considered to be reliable. 



The mean difference for all cruises surprisingly indicated that BT 

 siirface temperatures read by an oceanographer in the field are slightly 

 more accurate, although less consistent, than bucket temperatures. BT 

 temperatures were significantly more accurate than bucket temperatvires 

 during DELTA II and III. 



Normally, the field oceanographer read the BT trace using the manufac- 

 turer's grid setting. Occasionally, when a large variance (2° or 3°F) 

 existed between bucket and BT temperatures, the grid vas adjusted. 



15 



