7. Calculation of ice potential 



A technique currently utilized as a part of the sea ice prediction 

 program requires accurate thermal structure data. 



8. Calculation of currents from dynamic topography 



Very accurate temperature values are necessary to develop the 

 density structure from which general circulation can be determined. 



9. Temperature- salinity verification 



To check the validity of deep oceanographic data, use is made of 

 the temperature- salinity, or T-S, identification. 



B. ACCURACY AND SENSITIVITY 



For most of the uses of temperature data, a temperature accuracy 

 of ±0.1°C is sufficient. However, for buoyancy problems, temperatures 

 to an accuracy of ±0.05°C are desired. For calculations of dynamic 

 topography temperature values to ±0.02°C are necessary. 



Accuracy, however, is not the only requirement. The measuring 

 device should be sufficiently sensitive to describe the horizontal and 

 vertical variations in the temperature distribution and the changes in 

 distribution that are constantly occurring. This latter requirement 

 in some problems is at least equal to, if not more important than, 

 that of accuracy. The criteria for determining the desired sensitivity 

 are both the time factor of naturally occurring temperature variations 

 and the speed desired for lowering and raising the instruments. A 

 response time of 0.2 second for attaining 90 percent of a change of 

 5.0°C is desired. 



C. PRESENT TEMPERATURE MEASURING EQUIPMENT 



The greatest portion of the sea temperature observations on file at 

 the Hydrographic Office has been collected with four types of equip- 

 ment: bucket thermometer, intake thermometer, bathythermograph (BT), 

 and reversing thermometer. 



1. Bucket thermometer 



A large percentage of surface water temperatures has been 

 obtained by measuring the temperature of a water sample scooped up 



III -3 



