About 11 days after the injection, the bottom particle moves northwest and 

 continues until it hits the shore at Martha's Vineyard 20 days after injec- 

 tion. It should be noted that of the directional data reported by Bumpus 

 (1973), four data points were used (all at a speed of 3.0 nautical miles per 

 day) to advect the particle. 



2.3.6 Summary of Initial Modeling Results 



Five different models were used to predict or hindcast the movement of 

 the oil on the water surface, and, in general, they all were successful in 

 establishing the general direction of drift. Conceptually, they all con- 

 sidered the oil as Lagrangian particles which were advected along by the 

 currents and given a differential oil/water velocity related to the wind. 

 Difference arose in what the models used for the advecting current fields 

 and wind factors, and in the sources of the wind data (real-time winds, cll- 

 matological wind series, or stochastic models). 



In all cases the parameterizations were simple. The advective current 

 fields used were externally specified and were either a general mean current, 

 a predicted tide, or a correction term based on estimates of the errors in 

 the last model up-date. Nontidal time dependence or topographically control- 

 led regional currents were not modeled. The wind drift factor was intended 

 to represent the net effect of Ekman currents, Stokes drift, and momentum 

 transfer by waves. Options ranged from considering the Ekman drift explic- 

 itly, parametrically, or not at all. In all models some form of down-wind 

 motion was used, with the magnitude depending upon whether the Ekman drift 

 was considered separately or not. 



In general, the models reflect a wind-dominated transport for the oil, 

 and the real-time winds coincide fairly well in direction with the climatol- 

 ogically derived winds. This makes the model all behave in a similar manner, 

 and it is difficult to evaluate the relative accuracy of the slightly differ- 

 ent approaches. For the Avgo Mevahant the models all gave useful and en- 

 couraging results. A more critical test will come in an advectively domin- 

 ated region with complex coastal morphology. 



References 



Bumpus, Dean F. , 1973. A description of the circulation on the continental 

 shelf of the east coast of the United States. Progress in Oceanography 

 Vol. 6, pp. 111-157. 



Bureau of Land Management, 1976. Draft Environmental Statement for the Outer 

 Continental Shelf off the North-Atlantic States, U.S. Department of 

 Interior, Visual #2. 



Report of the Task Force - Operation Oil (Clean-up of the Arrow oil spill in 

 Chedabucto Bay, July 1970a, Canada Ministry of Transport. 



COMDT First Naval District letter to CNO file 3120 ser 153 of 4 Jun 1970b. 



63 



