APPENDIX C 



AN EVALUATION OF THE AIRBORNE RADIATION THERMOMETER FOR 

 THE INTERNATIONAL ICE PATROL 



by LTJG S. R. OSMER, USCG 



Late in the 1974 Season, an airborne radiation 

 thermometer (ART) was made available to Com- 

 mander, International Ice Patrol, and was de- 

 ployed for utilization and evaluation by the Ice 

 Patrol Detachment. In 1954 the Ice Patrol 

 conducted unsuccessful tests with an airborne ra- 

 diation thermometer for the purpose of distin- 

 guishing between iceberg and non-iceberg radar 

 targets under conditions of poor visibility. This 

 device was called a bolometer. During the 1964 

 season, an airborne radiation thermometer was 

 tested by the International Ice Patrol. While 

 the actual water temperatures recorded by this 

 instrument were not considered sufficiently re- 

 liable, the instrument was useful in detecting 

 changes in surface water temperature, and there- 

 fore in locating the approximate position of the 

 Labrador Current and its branches. 



The main reason Commander, International 

 Ice Patrol requested the ART was to, hopefully, 

 improve the operational efficiency of the flights 

 by determining sea surface temperature (SST) 

 in the vicinity of icebergs to provide optimum 

 deterioration data. Commander, International 

 Ice Patrol , on a regular basis, "melts" icebergs. 

 This "melt" is based upon conservative historical 

 temperature deterioration data. The resulting 

 survey could also map temperatures in the adja- 

 cent areas for continued iceberg melting as they 

 drift. 



Additionally, it was thought possible that the 

 Labrador Current could be monitored on a con- 

 tinuous basis during routine flights. Although 

 the Labrador Current is salinity driven, many of 

 its features can be identified from themal meas- 

 urements as can the northern wall and eddies of 

 the North Atlantic Current. These determina- 

 tions should then aid in predicting the direction 

 of iceberg drift due to surface currents. 



After a training period in June, the ART was 

 flown on thirteen (13) ice reconnaissance flights 

 in July. The normal altitude for such flights 

 was 1000 feet. The data collected were then 

 plotted and contoured. These isotherms were 

 compared with the mean sea surface tempera- 

 tures for July and the weekly SST charts pro- 

 duced by the Canadian Maritime Command 

 (MARCOM). The MARCOM SST charts are 

 used by the Ice Patrol Headquarters for the reg- 

 ular computing of iceberg life expectancy. These 

 SST data are displayed in figures C-l through 

 C-7. All temperatures are in degrees Celsius 

 (°C). 



Four Ice Patrol flights were made during 7 

 to 10 July, four flights during 16 to 20 July, and 

 five flights during 24 to 30 July. The flight 

 tracks are shown on the ART charts. The gaps 

 in data are due to the continuing problem Inter- 

 national Ice Patrol faces each year on the Grand 

 Banks — bad weather, in particular heavy fog, 

 rain, and low-lying clouds. The ART is weather- 

 limited in that the concentration of water vapor 

 in the sampling column will cause a biased read- 

 ing due to back radiation. Thus, if the surface 

 to be observed is obscured by weather the ART 

 cannot be used with any great weather reliability. 



The ART SST for 7 to 10 July shows a very 

 good agreement with the MARCOM Halifax 5 

 to 8 July SST. The 8° to 16° isotherms compare 

 very well< while the' 6° isotherm on the MAR- 

 COM chart tends to be further north and east 

 than as shown on the ART chart. 



For the next period, 16 to 20 July, the flights 

 were characterized by large gaps in data collec- 

 tion due to weather. This can be inferred from 

 the chart. The ART SST shows a fair compari- 

 son with the MARCOM SST for the 6° to 12° 

 isotherms. The 4° isotherm on the MARCOM 



