The radiation thermometer and infrared scanner were operated 

 simultaneously over the northern boundary of the Gulf Stream to 

 compare the response of the two instruments to large thermal gra- 

 dients. At Bermuda, both systems were operated over ARGUS ISLAND 

 to compare their response to small thermal contrasts. In addition, 

 radiation thermometer measurements were made at relatively high 

 altitudes over ARGUS ISLAND during daytime and nighttime flights 

 in order to determine altitude and diurnal effects on the absolute 

 accuracy of this device. 



Results 



Cape Hatteras to Bermuda : Radiation thermometer and infra- 

 red scanner data of 6 March 1966 are shown in figure 9« The tracks 

 were a northwest to southeast transect of the northern boundary of 

 the Gulf Stream near Cape Hatteras. 



The radiation thermometer record (top figure 9) shows that the 

 Gulf Stream's northern boundary consists of a series of thermal steps. 

 There are three major steps and a minor step to the southeast. The 

 gradient in each step was a nearly uniform )-i-.2 c/km. The actual 

 gradient was probably stronger since the radiation thermometer time 

 constant (about 2 seconds) limits any gradient to about 4.2°c/km. 

 The total temperature steps (progressing from northwest to southeast) 

 were 2.0°, I.3 , k.0°, and 0.3°C. 



Flight Over ARGUS Tower : Figure 10 shows the results of 

 a north -to -south flight over ARGUS ISLAND with the radiation ther- 

 mometer on 8 March. The tower appears as a spike near the middle of 

 the radiation thermometer record. 



The radiation thermometer shows a fairly smooth temperature 

 distribution in the water around the tower with a warming trend to 

 the north. Since the shallow water of Plantagenet Bank lies north 

 of the tower, the O.3 to 0A°C warming trend is probably a result 

 of insolation in this area. This warmer region did not appear on the 

 scanner record owing to the small gradient. 



Bermuda to Cape Hatteras : On the return flight on 12 March, 

 the northern boundary of the Gulf Stream was crossed at about 1700Z 

 (figure 11). The flight pattern duplicated the outbound track on 

 6 March. 



The radiation thermometer record (top figure 11) shows the Gulf 

 Stream (on the right) to be about 21°C. Near the boundary the 

 temperature began to drop gradually, then rapidly, until approximately 

 13 C. From the appearance of the record, the 13 C water is apparently 

 a cold band intruding into the uniformly cooling interface water. 



13 



