APPENDIX E 



OBSERVATIONS OF SEA SURFACE TEMPERATURES IN THE 

 VICINITY OF THE GRAND BANKS 



H. G. KETCHEN, LT, USCG 

 Staff Oceanographer 

 International Ice Patrol 



The International Ice Patrol has an opera- 

 tional need for reliable, accurate sea surface 

 temperature (SST) data in the vicinity of the 

 Grand Banks to be used in the prediction of ice- 

 berg deterioration rates and definition of certain 

 ocean current regimes. The Grand Banks offers 

 one of the most dynamically active ocean areas 

 in the world with the cold, narrow Labrador 

 Current meeting the warm North Atlantic Cur- 

 rent. This situation, complicated by the fact that 

 both currents constantly vary in magnitude and 

 position, account for relatively rapid changes in 

 oceanographic features, including SST. To 

 maintain a useful plot of SST data, frequent 

 updates are needed. Ice Patrol presently re- 

 ceives SST reports from merchant vessels tran- 

 siting the area, hourly from the Ice Patrol 

 Oceanographic Research Vessel (USCGC EVER- 

 GREEN) when in the vicinity of the Grand 

 Banks, from airborne radiation thermometer 

 (ART) surveys conducted on routine ice recon- 

 naissance flights and from satellite infrared 

 imagery. 



Due to the remoteness of the Grand Banks 

 area, ship reports are infrequent. Even with 

 U.S. Coast Guard Oceanographic Cutter EVER- 

 GREEN reporting hourly SST's, vessels alone 

 cannot provide the coverage and density of 

 samples necessary to develop the SST contours 

 needed by Ice Patrol. 



In the latter part of the 1974 Ice Season, Ice 

 Patrol began its first operational use of the ART. 

 Although IIP had experimented with infrared 

 recording devices for a number of years 

 (OSMER, 1974), this marked the first time the 

 ART had been used operationally on the Grand 

 Banks. The first recorded use of an infrared 



device for measuring water temperatures from 

 an aircraft, was by Woods Hole Oceanographic 

 Institute in surveying the Gulf Stream 

 (STOMMEL et al, 1953). They found that an 

 airborne infrared detector was capable of pro- 

 viding a chart of surface thermal gradients over 

 a much greater area than could be covered by 

 surface vessels, and in a much shorter time. 

 Continuing research using the Stommel-Parsons 

 instrument, they developed a series of thermal 

 gradient charts that defined the fine structure of 

 the Gulf Stream front (VON ARX et al, 1955). 

 With the potential value of the instrument de- 

 termined, its use became more widespread. 



Using a more sensitive instrument manufac- 

 tured by the Barnes Engineering Company, 

 Richardson and Wilkens (1958) reported the 

 existence of certain errors in sea surface radia- 

 tion measurements from aircraft. These ap- 

 peared to result primarily from the reflection of 

 solar radiation from the sea surface and the 

 atmospheric conditions at the time of recording. 

 The atmospheric errors were due to radiation 

 absorption by atmospheric water vapor in the 5 

 to 7 micrometer band, and by carbon dioxide in 

 the 14 to 16 micrometer band; thus the 8 to 13 

 micrometer window was found to be most useful 

 for infrared remote sensing (KETCHEN et al, 

 1977). 



International Ice Patrol has been using the 

 Barnes PRT-5 for ART surveys, operating with 

 a 9.5 to 11.5 micrometer window while flying at 

 altitudes of 1000 feet or lower. Even with this 

 window, any appreciable amount of water vapor 

 in the air column between the aircraft and the 

 water surface (including light fog, thin cloud 

 cover and 1 water spray from strong surface 



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