Distance (feet) Time 



^.eft-center pill Left-right pill (seconds) 



89 183 



93 171 10 



(91) (178) 97 



101 - 100 



85 165 214 



Combining sequence Nos. 4 and (Photographs 35 and 36, Appendix III), pro- 

 duces a differential velocity of 0.11 knot. Sequence Nos. 2 and also yield 

 a differential velocity of 0.11 knot directly downwind. Sequence Nos. 1 and 

 3 are too close in time to and 2 to give additional differential velocity 

 values, but are indicative of the precision of the method, i.e., about +10^' 

 Since the USCGC Vigilant recorded a wind speed of 10 knots from 250° at 1100 

 on December 19, the differential velocity obtained in this measurement 

 equates to 1.1% (+ 0.1%) of the wind speed. Simultaneously with the above 

 differential velocity experiment, a Richardson current probe was deployed in 

 the same area. Two photographs of this probe give a mean surface current 

 velocity of 1.6 knots (+5 to 10%). Visual observation of the current probe 

 yielded an estimated separation distance of 200 feet, while the two photo- 

 graphs yielded 186 feet and 206 feet respectively. The current direction was 

 estimated to be 205° using wind wave directions as reference. 



The second set of measurements was obtained on December 20, when the 

 helicopter hovered over a series of five dye pills at altitudes of 500 to 

 1500 feet for 20 minutes. Using visual distance measurements with the USCG 

 viewfinder, J. Mattson and D. Kennedy of the SOR Team measured the speed with 

 which a pancake overtook a dye marker. In this instance, the speed was about 

 0.20 knots. The Vigilant reported winds of 17 knots headed 015° at the time 

 (1200 EST, December 20) , which yields another differential oil/water velocity 

 of 1.1 to 1.2% of the wind speed. A Richardson current probe deployed at 

 that time yielded a surface current of 1.3 knots at 030°, about 15° to the 

 right of the wind. 



Additional differential velocity measurements were made on December 19 

 at 1245 from a fixed-wing aircraft, and on December 22, 1976, from a USCG 

 helicopter. A summary of all differential velocity measurements is contained 

 in Table 2-3. 



2.2.5 Water Mass Measurements 



Expendable bathythermographs (XBTs) were taken during several of the 

 cruises conducted in response to the oil spill. The locations are shown in 

 Figure VII-7 in appendix VII. Eleven were obtained from the first Delaware 

 II cruise on December 22 and 23, while 43 were obtained from the second 

 Delaware II cruise on January 4. Eighty-three XBT stations (not plotted) 

 were taken during cruise 17 of the Oceanus (December 3-9, 1976) and 15 XBTs 

 were acquired during Oceanus cruise 20 (every station except 13) . 



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