OBSERVATIONS OF SOME PHYSICAL FACTORS AFFECTING THE USE OF AN AIRBORNE 

 RADIOMETER 



by James L. Squire, Jr., Tiburon Marine Laboratory, 

 Tiburon, California 



The physical parameter of sea surface temperature in relation to the distribution and 

 abundance of important eastern Pacific marine fishes has been of interest to the biological 

 oceanographer for at least four decades. A rapid sjTioptic survey of this environmental 

 parameter is needed to test its correlation with the occurrence of pelagic migratory fishes. 

 An observation on the possibility of obtaining rapid, nearly synoptic ocean surface tempera- 

 ture surveys using airborne infrared equipment was made by Ewing (1952) as the result of 

 conducting experimental surveys in the tropical eastern Pacific. In the fall of 1962 the 

 Tiburon Marine Laboratory began experiments and field surveys using an airborne infrared 

 radiometer. To date, the instrument has been used in five types of aircraft (Cessna 172, 

 Champion, Grumman UF (Albatross), Martin P5M and P2V) for a total of approximately 310 

 hours of airborne operations. 



A Barnes Engineering Company model 14-312 radiometer mounted in a Cessna 172C 

 was used in initial field tests and surveys. A series of water surface observations was 

 made at several elevations and compared with simultaneous observations taken at water level 

 (see section on meteorological effects). Repeatability tests were run from upper Tomales 

 Bay, California, to over the Pacific, an area where differences in water temperatures were 

 available over a short geographical distance. Repeatability within a short period of time 

 (5-15 minutes) of surface water measurements taken at selected points along the flight 

 track to < -0.5°. was indicated. These observations were published by the Barnes Engin- 

 eering Company (Anon. 1962). 



« 



Surveys were made of nearshore temperatures (1/2 to 1 mile offshore) from Cape 

 Flattery, Washington, to Mexico and of the waters from north San Francisco Bay to a point 

 north of Sacramento, California, on the Sacramento River, and of the marine outfalls of 

 steam-electric generating plants. In April 1963, surveys were conducted at 24 hour inter- 

 vals for four days, of the Santa Barbara channel as part of Operation C.O.W. (Cooperative 

 Observational Week (Frank, I960)). Observations of temperature gradients in relation to 

 wind flow patterns in situations of wind velocities of less than 1 knot to greater than 25 knots 

 were observed over a short geographical distance. 



In August 1963, monthly IRT (infrared thermometer) survey flights of three West 

 Coast continental shelf areas were initiated in cooperation with the U. S. Coast Guard. The 

 IRT flights are continuing and sea surface isotherm charts are published by the Tiburon 

 Marine Laboratory for each area. 



IRT airborne instruments and accessories presently used for monthly surveys are 

 listed as follows: 



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