Since sea steam which is much thinner than sea fog is a rather common phenomenon, parti- 

 cularly in cold seasons (Von Arx, 1962), caution should be taken for the use of IRT in such 

 occasions. Also, accurate measurements of the trans mis sivity t in the presence of sea fog 

 or sea steam will give us information on congregate structures of water droplets. 



It is notable that the effect of air temperature is negligible when the air is much 

 warmer than the water as indicated in later calibration (Aug. 6, 1964), in which the entire 

 experimental set-up was the same as in that of Figure 3. The results indicate that the AT 

 (=:Ti - Tw) is -0,4° to 0.9°F for the range of Tw from 51° to 78° F with the air temperature 

 82° to 86° F at the air path of 9.9 meters. There is almost no correlation between the values 

 of AT and Tw and thus the differences AT seem to be caused by other effects than those of 

 water vapor. Since in this experiment the air temperature was higher than the water tem- 

 perature, the air layer close to the water surface was stable and evaporation was also very 

 small. 



CONCLUSIONS 



(1) Effect of the temperature of the air column between the sensor and the water 

 becomes important when the air-sea temperature difference exceeds 10.0°F. 



(2) The distance between the sensor and the water also influences the IRT readings. 



(3) The effect of angle of the sensor becomes serious when the angle exceeds 40°. 



(4) The snow or rain might substantially affect the IRT values. 



(5) The IRT is useful to detect tide lines or ship's wake. 



(6) The rhodamine "B" or fluorescein dye causes an increase in IRT readings. 



ACKNOWLEDGMENT 



The present work is supported jointly by Contract Nonr 266(48) with the Office of 

 Naval Research and by Contract AT(30-1)2663 with the Atomic Energy Commission. 



REFERENCES 



Clark, J. and R. Stone, 1964: The use of the infrared thermometer in routine coastal sur- 

 vey — a summary. Workshop Contribution. 



Frank, J. L., 1964: The accuracy of airborne infrared thermometry. Workshop Contribution. 



Gaul, R.D., 1963: Status of environmental research off Panama City, Florida, Technical 

 paper A and M College of Texas, Project 286 (D), Ref. 63-2T. p. 82 



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