possible interference by air turbulence, acoustics, vibration, and shock. The result of 

 these was to show that the most serious interfering influence on the instrument is air 

 turbulence. In tests made to compare ART airborne readings with conventional sea- surface 

 temperature measurements, large differences observed could usually be explained on the 

 basis of water vapor or other known factors. A difference of as much as 1.7°C has been 

 observed. A formula for the correction of water vapor in the air column which was develop- 

 ed by the Weather Bureau was given and discussed. The relation between ART survey and 

 the Synoptic Oceanographic Analysis Program of the Navy was also presented. Generally 

 it can be expected that the ART readings will estimate actual sea- surface temperature 

 within ±0.4° F., but larger errors which must be continually watched for are caused either 

 by instrument problems or unusual enviromental conditions. The Navy considers the 

 primary value of the IRT survey to be in the location of gradients and fronts rather than 

 absolute temperature. The use of the ART is estimating layer depth was demonstrated by a 

 graph showing a negative relation between layer depth and surface temperature. This is 

 important because layer depth is a major factor in determining sonar conditions. 



In the discussion that followed it was brought out by Mr. Moser that the more sensi- 

 tive types of equipment give rise to a completely different set of problems in relation to 

 "sea-noise". The greatest variation seems to occur when the sea is either calm or rough, 

 but at sea states between 1 and 3 the "quietest" pictures are obtained. It was brought out 

 that one source of variation could be eliminated if the "chopper" wheel were not located 

 between the lenses. It was also brought out that occasionally the temperature of the lens 

 was monitored on Navy flights, but that no airborne calibration checks could be made. 



John P. Tully ; Airborne Radiation Thermometer on the Pacific Coast of Canada 



A cooperative IRT survey program is being set up for the North Pacific Ocean by 

 interested Canadian agencies. The object of this is to install unattended airborne IRT into 

 routine military air patrol craft in order to collect a large amount of surface temperature 

 data from the North Pacific at low cost. Experience was obtained initially with Richardson's 

 unit loaned from the Woods Hole Oceanographic Institute and later with a specially built 

 instrument using a Barnes bolometer. At the present time a new model for use in the new 

 program is in the final stages of completion. Of the five units which are being completed, 

 two are for survey on the Atlantic Coast, two on the Pacific Coast, and one for special 

 assignments. Dr. Tully noted that the equipment measures apparent radiation which varies 

 because the ambient variation of sea surface temperature is at least 1°C. He argued that 

 both military and fisheries were concerned primarily with temperature structure in the sea 

 and that temperature perse was secondary. One-degree accuracy was sufficient for most 

 purposes. The structure in the sea, occurrence of transients, fronts, etc., are revealed by 

 the character of the recorder "signature" and are a function of sensitivity of the equipment 

 rather than accuracy. 



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