Measurements of the Sea Surface Temperature on the Eastern 

 Pacific Continental Shelf Using Airborne Infared Radiometry 



James L. Squire, Jr.^ 



INTRODUCTION 



The sea above the eastern Pacific Continental 

 Shelf — a narrow strip of the total marine en- 

 vironment — is a productive area of the Pacific 

 for both plankton and nekton. However, the 

 complex oceanography of the nearshore area is 

 little known, particularly in regard to factors 

 affecting the distribution and migration of its 

 fishery resources. One physical parameter of the 

 ocean environment that is easily measured is 

 sea surface temperature. The relation between 

 sea surface temperature in the eastern Pacific 

 and the distribution and migration of marine 

 and anadromous fishes has long interested 

 fishery biologists. Since this relation provides a 

 possible means of predicting variations in dis- 

 tribution of important marine species, there is 

 an increasing interest in monitoring coastal sea 

 surface temperatures (Hester, 1961; Johnson, 

 1961; Johnson, Flittner, and Cline, 1965). Dur- 

 ing years of unusually warm water, southern 

 species have been recorded north of their usual 

 range (Hubbs and Schultz, 1929; Walford, 

 1931 ; Radovich, 1961) , and variations from the 

 normal pattern of coastal migration have been 

 observed in such species as salmon (Royal and 

 Tully, 1961). 



Average sea surface temperature isotherm 

 charts with 2°F contours, based primarily on 

 1-degree longitude by latitude averages of 

 National Weather Service ship observation 

 data, are issued bimonthly by the National 

 Marine Fisheries Service to provide a partial 

 basis for prediction of albacore (Thunnus 

 alalunga) and bluefin tuna (Thunnus thynnus) 

 catch distribution (Johnson et al., 1965). A 

 variety of mean and anomaly sea surface tem- 

 perature charts for the North Pacific, as well 

 as other oceans and seas in the Northern Hemi- 



National Marine Fisheries Service, Tiburon Marine 

 Laboratory, Tiburon, Calif. 



sphere, is computed daily by the U.S. Navy 

 Fleet Numerical Weather Central, Monterey, 

 Calif. (Wolff, 1968). The Canadian Government 

 issues semiweekly sea surface temperature 

 charts (1°F) isotherm contours for the north- 

 eastern Pacific. Though these programs obtain 

 data on sea surface temperatures above the 

 eastern Pacific Continental Shelf, the limited 

 number of observations during any one day 

 limits the development of detailed isotherm 

 charts for use within local fishing areas. 



One of the problems in determining the rela- 

 tionship of the distribution and movement of 

 pelagic fishes to temperature change has been 

 the lack of an economically feasible means of 

 determining sea surface temperature nearly 

 instantaneously over a large geographical area. 

 The airborne infrared radiation thermometer 

 (ART) provides a rapid means of measurement 

 to fill this need. In August 1963, monthly survey 

 flights of three eastern Pacific Continental Shelf 

 areas (fig. 1) were initiated in cooperation 

 with the U.S. Coast Guard as part of their 

 commitment in support of the national oceano- 

 graphic program. The three areas selected for 

 survey were important coastal fishing areas and 

 of different physical oceanography — a gyral 

 area off southern California, an upwelling area 

 off central California, and a coastal area off 

 Oregon and Washington, which is under direct 

 influence of a southern segment of the North 

 Pacific Current. 



This paper reviews the technique of airborne 

 infrared measurement of sea surface tempera- 

 ture and is a report on the progress of the 

 cooperative program for a 5-year period (Au- 

 gust 1963 through July 1968) . 



INFRARED RADIOMETRY 



Temperature measurements of remote objects 

 are possible because all objects with tempera- 



