increased. It should be noted that differences of less than about 0.4°F are within the accuracy 

 limits of instrument calibration. The meteorological and oceanographic conditions during 

 these tests are shown below: 



Wind speed 10-12 knots 



Wave height 2-4 feet 



Air temperature (surface) 66°-67°F 



Rel. humidity 85-90% 



Cloud cover 2/10 



In evaluation of these comparisons, ART temperatures are at best only approxima- i 

 tions of the temperature of the water at the base of the tower. Although the ART temperatures 

 at the base of the tower are fixed precisely by the edge of the thermal signature of the tower, 

 they represent the temperature of sea surface over at least 150 feet as shown by the equivalent 

 distance scale for two examples in figure 6. The width of the recorded trace corresponds to a 

 distance of about 150 feet aloi^ the flight path of the aircraft at a recording speed of 2 inches 

 of chart per minute. 



On 20 and 21 November 1963, measurements of sea surface temperatures were made 

 over shallow water south of New Providence Island in the Bahamas. As the aircraft passed 

 overhead, surface temperatures were recorded by a ship with bucket and reversing thermo- 

 meters and with a continually recording towed temperature probe. Twenty passes were made 

 over the ship at an altitude of 100 feet followed by ten passes at 1,500 feet. The differences | 

 between the ART and the three shipboard measurements, as well as mean differences for 

 each group of data, are shown in tables 3 and 4. 



The ART readings at 100 feet compared most favorably with bucket and reversing 

 thermometer measurements and showed a net drop of temperature when altitude was increased 

 to 1,500 feet. The average difference between the ART and the three shipboard measuring 

 devices, -0.30°F at 100 feet, is within the accuracy limits of instrument calibration. However, 

 the average difference between the ART and three shipboard devices at 1,500 feet was about 

 -1.0°F. The correction for water vapor using the previously introduced expression was 

 about +0.04°F for 100 feet of altitude and about +0.4°F for 1,500 feet. 



During these tests, surface temperature varied between 76° and 78.5°F, and relative 

 humidity was about 75 percent. Winds were light, waves ranged from 2 to 3 feet, and cloud 

 cover was about l/lO. 



Unlike the tower, the ship gave no thermal signature on the ART recording. This made 

 selection of corresponding temperatures for comparison less precise. Figure 7 shows two 

 examples of the ART recordings with signals indicating when the aircraft was directly over- 

 head from observers, both in the aircraft and aboard ship. These observations are separated in 



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